tag:theconversation.com,2011:/us/topics/turbulence-27407/articlesTurbulence – The Conversation2024-02-09T00:36:19Ztag:theconversation.com,2011:article/2228532024-02-09T00:36:19Z2024-02-09T00:36:19ZHigher, faster: what influences the aerodynamics of a football?<figure><img src="https://images.theconversation.com/files/573580/original/file-20240203-27-i63qjv.jpg?ixlib=rb-1.1.0&rect=0%2C0%2C5472%2C3579&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">In addition to a player's ability to throw it, a number of factors will influence a ball's flight, including its size, inflation pressure and texture.</span> <span class="attribution"><span class="source">(Shutterstock)</span></span></figcaption></figure><p>With <a href="https://www.nfl.com/news/super-bowl-lvii-averages-audience-of-113-million-viewers-fox-sports">113 million viewers in the United States</a> and 40 million more around the world, the Super Bowl is the most popular sports event in North America. This year’s event on Sunday – with the added attraction of a <a href="https://www.cnn.com/videos/sports/2024/02/06/super-bowl-players-vegas-taylor-swift-wire-nc-vpx.cnn">romance in the spotlight</a> – promises to attract as many fans.</p>
<p>In Canada, the most recent Grey Cup final, last November, reached a <a href="https://twitter.com/RDS_RP/status/1726722586816430330">record audience</a> of 3.7 million viewers who tuned in to watch the Montréal Alouettes’ victory.</p>
<p>The two leagues definitely don’t enjoy the same popularity – far from it. Nor do they have the same rules. But there is another difference: although similar in appearance, the famous oval balls used in football have specific characteristics on both sides of the border that can affect their aerodynamics, i.e. the forces exerted by the air on the ball during its flight. The design and characteristics of the ball have an impact on the magnitude of these forces.</p>
<p>It might be news to football players, but their talent for throwing balls long distances is not the only thing that matters. A number of factors affect the ball’s aerodynamics, including the way it is made and its inflation pressure.</p>
<p>As a professor in the Department of Mechanical Engineering at Québec’s École de technologie supérieure, I am interested in experimental fluid dynamics. I study the physics of fluid flows and certain applications (e.g. propulsion of aquatic vehicles, aerodynamic applications). Fluid dynamics is a vast field and affects many aspects of our lives, such as the flow of blood in the heart, the flight of aircraft, the beautiful swirling patterns in Jupiter’s atmosphere or the perfect football pass for a touchdown.</p>
<h2>Ball size affects flight stability</h2>
<p>The NFL and CFL have the same <a href="https://cfldb.ca/faq/equipment/#:%7E:text=The%20CFL%20football%20dimensions%20are,to%2028%201%2F2%20inches">rules</a> regarding the dimensions of their balls. They must be between 11" and 11.25" long. They must also be inflated to between 12.5 psi and 13.5 psi, giving them a maximum circumference of between 28" and 28.5" around the length and between 21" and 21.25" around the width.</p>
<p>These dimensions are important. The football acts like a gyroscope. The higher the speed of rotation, the more stable the ball will be during its flight. Different dimensions can therefore have specific effects on the stability of the ball’s flight.</p>
<figure class="align-center ">
<img alt="An American football player catches a ball in mid-flight on a field" src="https://images.theconversation.com/files/573219/original/file-20240203-25-y5at9n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/573219/original/file-20240203-25-y5at9n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=438&fit=crop&dpr=1 600w, https://images.theconversation.com/files/573219/original/file-20240203-25-y5at9n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=438&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/573219/original/file-20240203-25-y5at9n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=438&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/573219/original/file-20240203-25-y5at9n.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=551&fit=crop&dpr=1 754w, https://images.theconversation.com/files/573219/original/file-20240203-25-y5at9n.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=551&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/573219/original/file-20240203-25-y5at9n.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=551&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">The size of the football matters. The ball acts like a gyroscope. The higher the speed of rotation, the more stable the ball will be during its flight.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p>A larger circumference suggests that more of the ball’s mass is located away from its centre line. This means that it will have a higher moment of inertia (resistance to rotation) and, therefore, that the same force applied to make it rotate will result in a lower speed of rotation.</p>
<h2>Two stripes and laces make a difference</h2>
<p>While there are two white stripes on the Canadian ball, as well as laces, American rules don’t mention these.</p>
<p>The differences between the Canadian and American balls can have an effect on their drag. A drag force is the resistance to a moving object in a fluid. In this case, it is mainly the resistance caused by the air (a fluid), which is called form or pressure drag.</p>
<p>Let’s take the example of a golf ball. Its dimples encourage turbulence, which allows the airflow to stick to the ball and reduce its total drag. Less drag means the ball can fly further with the same force applied.</p>
<p>The laces on a football and any other significant modification to its surface (a logo, a valve), in combination with the rotation of the ball, will to some extent have the same effect. It would be interesting to study how <a href="https://www.engineering.com/story/the-aerodynamics-of-a-football">these differences</a> between NFL and CFL footballs affect their respective drag.</p>
<h2>NFL or CFL, which ball is better?</h2>
<p>To do this, we could use a wind tunnel (an experimental installation in the form of a tunnel with a controlled airflow) to simulate the movement of air (fluid flow) around the two balls that will be fixed in space, put into rotation and subject to an airflow speed that would imitate the balls’ speed of flight.</p>
<p>An aerodynamic force balance could be used to measure the differences in drag between the two balls subjected to the same conditions. Ideally, to eliminate other factors of variability, the two balls would have the same dimensions.</p>
<p>The passage of air around the ball could be visualized using smoke or particle image/tracking velocimetry. The latter is a method in which the air is seeded with particles (helium-filled soap bubbles or oil droplets). The movement of these particles could then be captured using a camera to quantify the airspeed at all points around the ball. This would allow regions of flow separation and recirculation to be seen, and provide an idea of the distribution of aerodynamic forces around the ball.</p>
<figure class="align-center ">
<img alt="A gloved hand holds a football on a grassy surface" src="https://images.theconversation.com/files/573221/original/file-20240203-21-3s2qf1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/573221/original/file-20240203-21-3s2qf1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/573221/original/file-20240203-21-3s2qf1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/573221/original/file-20240203-21-3s2qf1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/573221/original/file-20240203-21-3s2qf1.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/573221/original/file-20240203-21-3s2qf1.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/573221/original/file-20240203-21-3s2qf1.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">A ball about to be kicked. A number of factors will influence the aerodynamics of the ball.</span>
<span class="attribution"><span class="source">(Shutterstock)</span></span>
</figcaption>
</figure>
<p>Different rotation speeds and flight speeds could be examined, as there is always the possibility of developing flow instabilities, which would lead to a change in its behaviour around the ball. </p>
<p>This would help determine whether the NFL or CFL ball is better.</p>
<h2>Ball texture influences drag</h2>
<p>There is another type of drag, this one attributable to the friction between the air and the surface of the ball. This is called friction drag.</p>
<p>It depends mainly on the texture of the ball and its speed. The rougher the texture of the ball, the greater the friction drag for the same speed. Similarly, a faster ball speed will have a higher friction drag.</p>
<p>By reducing the form drag, we further reduce the total drag of the ball, which can therefore go further and faster on the football field.</p>
<h2>And then there’s the weather!</h2>
<p>The weather also plays a role in the aerodynamics of the football.</p>
<p>Cold or hot temperatures can affect the size of the ball by reducing or increasing the air pressure inside it.</p>
<p>Similarly, temperature can have some effect on the material properties of the ball, with colder temperatures making it stiffer and warmer temperatures making it softer.</p>
<p>Temperature and humidity also play a role in the physical properties of air, altering its density and viscosity.</p>
<p>Rain will also directly affect drag as, in a sense, it affects the texture of the ball’s surface as felt by the air.</p>
<p>But that won’t be an issue in Las Vegas on Feb. 11 for the Super Bowl game, since Allegiant Stadium is covered.</p><img src="https://counter.theconversation.com/content/222853/count.gif" alt="La Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Giuseppe Di Labbio ne travaille pas, ne conseille pas, ne possède pas de parts, ne reçoit pas de fonds d'une organisation qui pourrait tirer profit de cet article, et n'a déclaré aucune autre affiliation que son organisme de recherche.</span></em></p>A football’s dimensions, pressure and texture affect its aerodynamics, i.e. the forces exerted by the air on the ball as it flies.Giuseppe Di Labbio, Professeur adjoint, École de technologie supérieure (ÉTS)Licensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2217802024-01-24T17:39:08Z2024-01-24T17:39:08ZHere’s what happens to your body during plane turbulence – and how to reduce the discomfort it causes<figure><img src="https://images.theconversation.com/files/570863/original/file-20240123-19-j98p69.jpg?ixlib=rb-1.1.0&rect=0%2C12%2C8179%2C5444&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/woman-firmly-holds-mans-hand-during-1806710980">H Ko/Shutterstock</a></span></figcaption></figure><p>This week has seen another barrage of <a href="https://www.theguardian.com/uk-news/2024/jan/22/uk-weather-storm-jocelyn-to-follow-isha-with-more-strong-winds-and-heavy-rain">unsettled weather</a> sweep across the UK, with many flights delayed or cancelled. Some of those who were fortunate enough to take off found themselves arriving at destinations that weren’t on their boarding passes – such as passengers travelling from Stansted to Newquay who eventually diverted to <a href="https://uk.news.yahoo.com/storm-isha-creates-flight-diversion-142821278.html?">Malaga</a>.</p>
<p>One thing that was consistently described by passengers was that parts of the flights and the attempted landings were some of the most unnerving they’d ever experienced, due to turbulence.</p>
<p>Turbulence results from uneven air movement, which is <a href="https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2023GL103814">increasing</a> in frequency. If you turn your hair dryer on at home and hold it still, the air moves at a constant rate, but once you begin drying your hair and moving the hairdryer around, the air movement becomes uneven, that is to say, turbulent.</p>
<p>Although turbulence may be unnerving and make you feel unwell, it is important to recognise that it is very common and typically <a href="https://pubmed.ncbi.nlm.nih.gov/18018437/">nothing to worry about</a> if you’re in your seat with your seatbelt fastened.</p>
<h2>How the body detects and responds to turbulence</h2>
<p>The body recognises itself within any environment. Its relationship with objects in terms of distance and direction is called <a href="https://www.sciencedirect.com/science/article/abs/pii/B9780123750006003414">spatial orientation</a>. </p>
<p>When flying, this is typically moving forwards, ascending, some turns and a descent. However, turbulence disrupts this relationship and confuses the sensory information being received by the brain – it makes the body want to respond or recalibrate.</p>
<p>Our inner ears play a pivotal role in all this. It consists of complex apparatuses that undertake more than hearing. These include the cochlea, <a href="https://www.ncbi.nlm.nih.gov/books/NBK279394/">three semi-circular canals</a>, <a href="https://radiopaedia.org/articles/utricle-ear?lang=gb">the utricle</a> and <a href="https://radiopaedia.org/articles/saccule-ear-1?lang=gb">the saccule</a>. </p>
<p>The cochlea is responsible for hearing. It converts <a href="https://www.ncbi.nlm.nih.gov/books/NBK531483/">sound energy into electrical energy</a> that is then “heard” by the brain. The remaining structures are responsible for the balance and position of the head and body. The semi-circular canals are positioned in a vertical (side to side), horizontal and front-to-back plane, detecting movement in a nodding, shaking and touching ear-to-shoulder direction. </p>
<p>Attached to these canals are <a href="https://www.ncbi.nlm.nih.gov/books/NBK532978/">the utricle and saccule</a>, which can detect <a href="https://www.ncbi.nlm.nih.gov/books/NBK10792/">movement</a> and <a href="https://www.cell.com/current-biology/pdf/S0960-9822(05)00837-7.pdf">acceleration</a>. </p>
<p>All of these apparatuses use microscopic hair cells in a specialised fluid called <a href="https://www.ncbi.nlm.nih.gov/books/NBK531505/">endolymph</a> that flows with the head to create a sense of movement. When the plane encounters turbulence, this fluid moves around, but unpredictably. It takes <a href="https://www.ncbi.nlm.nih.gov/books/NBK518976/">about ten to 20 seconds</a> for the fluid to recalibrate its position, while the brain struggles to understand what is going on.</p>
<p>When the aircraft hits turbulence, the balance apparatus <a href="https://www.frontiersin.org/articles/10.3389/fneur.2023.949227/full">cannot distinguish</a> the movement of the plane from that of the head, so the brain interprets the aircraft movement as that of the head or body. But this doesn’t match the visual information being received, which causes sensory confusion.</p>
<p>The reason the inner ear causes so much confusion is because during flights you are devoid of your primary sensory tool relative to the external environment – your sight and the horizon. </p>
<p>Eighty per cent of <a href="https://www.ncbi.nlm.nih.gov/books/NBK518976/">spatial information</a> comes from your eyes during flight. However, you only have the seat in front of you or the cabin as a reference point, which means your inner ear becomes the dominant sensory message to the brain during turbulence and disrupts the <a href="https://www.ncbi.nlm.nih.gov/books/NBK545297/">“vestibulo-ocular reflex”</a>. This reflex keeps your vision <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4130651/">aligned</a> with your balance or expected position. </p>
<p>Vision is the <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6777262/">most valued</a> of the senses and one-third of the brain is attributed to its function, reinforcing its importance in spatial orientation.</p>
<p>This sensory mixed messaging often results in things like dizziness and sweating as well as gastrointestinal symptoms, such as <a href="https://www.airmedicaljournal.com/article/S1067-991X(02)70038-2/fulltext">nausea and vomiting</a>. </p>
<p>Motion sickness can be triggered by turbulence and although research into specific airsickness is limited, other modes that induce motion sickness suggest that <a href="https://pubmed.ncbi.nlm.nih.gov/16018346/">women</a> are <a href="https://pubmed.ncbi.nlm.nih.gov/26466829/">more susceptible</a> than men, particularly in the <a href="https://pubmed.ncbi.nlm.nih.gov/16235881/">early stages</a> of the menstrual cycle. </p>
<p>The turbulence also causes an increase in your heart rate, which is already higher than normal when flying because of a <a href="https://pubmed.ncbi.nlm.nih.gov/15819766/">decrease in oxygen saturation</a>.</p>
<h2>What about the pilots?</h2>
<p>Commercial pilots accrue thousands of hours at the controls, they are subject to the same forces as the passengers. </p>
<p>Over time, they can <a href="https://academic.oup.com/milmed/article/180/11/1135/4160573">adapt to these forces</a> and <a href="https://pubmed.ncbi.nlm.nih.gov/15828634/">experiences</a>, but they also have a couple of additional resources that most passengers don’t. </p>
<p>They have the view out of the cockpit windows, so have a horizon to use as a reference point and can see what lies immediately ahead. </p>
<p>If it is cloudy or visibility is low, their instruments provide additional visual <a href="https://www.faa.gov/sites/faa.gov/files/regulations_policies/handbooks_manuals/aviation/phak/19_phak_ch17.pdf">reference</a> to the position of the aircraft. This doesn’t mean they are immune to the effects of turbulence, with some studies reporting up to <a href="https://pubmed.ncbi.nlm.nih.gov/26540704/">71% of trainee pilots</a> reporting episodes of airsickness.</p>
<h2>How to reduce the discomfort</h2>
<p>A window seat can help, or even looking out the window. This gives the brain some sensory information through visual pathways, helping calm the brain in response to the vestibular information it is receiving.</p>
<p>If you can get one, a seat towards the front or over the wing reduces the effects of turbulence.</p>
<p>Deep or rhythmical breathing can help reduce motion sickness induced by turbulence. Focusing on your breathing <a href="https://pubmed.ncbi.nlm.nih.gov/25945662/">calms the nervous system</a>.</p>
<p>Don’t reach for the alcohol. While you may feel it calms your nerves, if you hit turbulence it’s going to interfere with your <a href="https://pubmed.ncbi.nlm.nih.gov/7610847/">visual and auditory processing</a> and increase the likelihood of vomiting.</p>
<p>If you suffer from motion sickness and are worried about turbulence while flying, then there are also <a href="https://www.ncbi.nlm.nih.gov/pmc/articles/PMC6241144/">drugs that can help</a>, including certain <a href="https://www.nhs.uk/medicines/cinnarizine/about-cinnarizine/">antihistamines</a>. </p>
<p>Finally, it’s important to remember that although turbulence can be unpleasant, aircraft are designed to withstand the forces it generates and many passengers, even frequent fliers, will rarely encounter the most severe categories of turbulence because pilots actively plan routes to avoid it.</p><img src="https://counter.theconversation.com/content/221780/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Adam Taylor does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>An anatomist explains why turbulence on flights makes us feel so ill and disoriented.Adam Taylor, Professor and Director of the Clinical Anatomy Learning Centre, Lancaster UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/2069202023-06-20T18:25:21Z2023-06-20T18:25:21ZHurricanes push heat deeper into the ocean than scientists realized, boosting long-term ocean warming, new research shows<figure><img src="https://images.theconversation.com/files/532027/original/file-20230614-23-paym8a.png?ixlib=rb-1.1.0&rect=1182%2C376%2C2629%2C1747&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Satellite data illustrates the heat signature of Hurricane Maria above warm surface water in 2017.</span> <span class="attribution"><a class="source" href="https://climate.nasa.gov/explore/ask-nasa-climate/3181/a-force-of-nature-hurricanes-in-a-changing-climate/">NASA</a></span></figcaption></figure><p>When a hurricane hits land, the destruction can be visible for years or even decades. Less obvious, but also powerful, is the effect hurricanes have on the oceans. </p>
<p>In a <a href="https://doi.org/10.1073/pnas.2301664120">recent study</a>, we show through real-time measurements that hurricanes don’t just churn water at the surface. They can also push heat deep into the ocean in ways that can lock it up for years and ultimately affect regions far from the storm.</p>
<p>Heat is the key component of this story. It has long been known that hurricanes <a href="https://www.whoi.edu/know-your-ocean/did-you-know/how-does-the-ocean-affect-storms/">gain their energy from warm sea surface temperatures</a>. This heat helps <a href="https://youtu.be/wPDoIrGUrEc">moist air near the ocean surface rise</a> like a hot air balloon and form clouds taller than Mount Everest. This is why hurricanes generally form in tropical regions.</p>
<p>What we discovered is that hurricanes ultimately help warm the ocean, too, by enhancing its ability to absorb and store heat. And that can have far-reaching consequences.</p>
<figure class="align-center ">
<img alt="Schematic showing the formation of a hurricane, which gains its energy from warm ocean surface water." src="https://images.theconversation.com/files/531237/original/file-20230611-186962-ohn2oi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/531237/original/file-20230611-186962-ohn2oi.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=262&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531237/original/file-20230611-186962-ohn2oi.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=262&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531237/original/file-20230611-186962-ohn2oi.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=262&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531237/original/file-20230611-186962-ohn2oi.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=329&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531237/original/file-20230611-186962-ohn2oi.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=329&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531237/original/file-20230611-186962-ohn2oi.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=329&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">How hurricanes draw energy from the ocean’s heat.</span>
<span class="attribution"><a class="source" href="https://commons.wikimedia.org/wiki/File:Hurricane-en.svg">Kelvin Ma via Wikimedia</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>When hurricanes mix heat into the ocean, that heat doesn’t just resurface in the same place. We showed how underwater waves produced by the storm can push the heat <a href="https://doi.org/10.1073/pnas.2301664120">roughly four times deeper</a> than mixing alone, sending it to a depth where the heat is trapped far from the surface. From there, deep sea currents can transport it thousands of miles. A hurricane that travels across the western Pacific Ocean and hits the Philippines could end up supplying warm water that heats up the coast of Ecuador years later.</p>
<h2>At sea, looking for typhoons</h2>
<p>For two months in the fall of 2018, we lived aboard the research vessel Thomas G. Thompson to record how the Philippine Sea responded to changing weather patterns. As <a href="https://scholar.google.com/citations?user=c9pivSIAAAAJ&hl=en">ocean</a> <a href="https://scholar.google.com/citations?user=kAGkuGgAAAAJ&hl=en">scientists</a>, we study turbulent mixing in the ocean and hurricanes and other tropical storms that generate this turbulence.</p>
<p>Skies were clear and winds were calm during the first half of our experiment. But in the second half, three major typhoons – as hurricanes are known in this part of the world – stirred up the ocean. </p>
<figure class="align-right ">
<img alt="A photo of an instrument being lowered into the ocean. It's a long thin line with sensors attached." src="https://images.theconversation.com/files/531240/original/file-20230611-22144-y4s1b9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/531240/original/file-20230611-22144-y4s1b9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=800&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531240/original/file-20230611-22144-y4s1b9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=800&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531240/original/file-20230611-22144-y4s1b9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=800&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531240/original/file-20230611-22144-y4s1b9.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1005&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531240/original/file-20230611-22144-y4s1b9.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1005&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531240/original/file-20230611-22144-y4s1b9.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1005&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Microstructure profilers are used to measure ocean turbulence. This one is designed and built by the Ocean Mixing Group at Oregon State University.</span>
<span class="attribution"><span class="source">Sally Warner</span></span>
</figcaption>
</figure>
<p>That shift allowed us to directly compare the ocean’s motions with and without the influence of the storms. In particular, we were interested in learning how turbulence below the ocean surface was helping transfer heat down into the deep ocean.</p>
<p>We measure ocean turbulence with an instrument called a microstructure profiler, which free-falls nearly 1,000 feet (300 meters) and uses a probe similar to a phonograph needle to measure turbulent motions of the water. </p>
<h2>What happens when a hurricane comes through</h2>
<p>Imagine the tropical ocean before a hurricane passes over it. At the surface is a layer of warm water, warmer than 80 degrees Fahrenheit (27 degrees Celsius), that is heated by the sun and extends roughly 160 feet (50 meters) below the surface. Below it are layers of colder water. </p>
<p>The <a href="https://youtu.be/H5-ZW8sH9ws">temperature difference</a> between the layers keeps the waters separated and virtually unable to affect each other. You can think of it like the division between the oil and vinegar in an unshaken bottle of salad dressing.</p>
<p>As a hurricane passes over the tropical ocean, its strong winds help stir the boundaries between the water layers, much like someone shaking the bottle of salad dressing. In the process, cold deep water is mixed up from below and warm surface water is mixed downward. This causes surface temperatures to cool, allowing the ocean to absorb heat more efficiently than usual in the days after a hurricane.</p>
<p>For over two decades, scientists <a href="https://news.mit.edu/2010/hurricane-thermostate-0304">have debated</a> whether the warm waters that are mixed downward by hurricanes could heat ocean currents and thereby shape global climate patterns. At the heart of this question was whether hurricanes could pump heat deep enough so that it stays in the ocean for years.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/531238/original/file-20230611-82779-r41xfk.png?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="Schematic with five stages showing the ocean's warm surface layer mixing during a hurricane, heat continuing to be pushed down after the hurricane passes and remaining there for months." src="https://images.theconversation.com/files/531238/original/file-20230611-82779-r41xfk.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/531238/original/file-20230611-82779-r41xfk.png?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=206&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531238/original/file-20230611-82779-r41xfk.png?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=206&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531238/original/file-20230611-82779-r41xfk.png?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=206&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531238/original/file-20230611-82779-r41xfk.png?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=258&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531238/original/file-20230611-82779-r41xfk.png?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=258&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531238/original/file-20230611-82779-r41xfk.png?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=258&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">These illustrations show what happens to ocean heat before, during, after and many months after a hurricane passes over the ocean.</span>
<span class="attribution"><span class="source">Sally Warner</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>By analyzing subsurface ocean measurements taken before and after three hurricanes, we found that underwater waves transport heat roughly four times deeper into the ocean than direct mixing during the hurricane. These waves, which are generated by the hurricane itself, transport the heat deep enough that it cannot be easily released back into the atmosphere.</p>
<h2>Implications of heat in the deep ocean</h2>
<p>Once this heat is picked up by large-scale ocean currents, it can be transported to distant parts of the ocean. </p>
<p>The heat injected by the typhoons we studied in the Philippine Sea may have flowed to the coasts of Ecuador or California, following current patterns that carry water from west to east across the equatorial Pacific. </p>
<p>At this point, the heat may be mixed back up to the surface by a combination of <a href="https://doi.org/10.1007/s10236-005-0115-1">shoaling currents</a>, <a href="https://oceanservice.noaa.gov/facts/upwelling.html">upwelling</a> and <a href="https://doi.org/10.1038/nature12363">turbulent mixing</a>. Once the heat is close to the surface again, it can warm the local climate and affect ecosystems. </p>
<p>For instance, coral reefs are particularly sensitive to extended periods of heat stress. El Niño events are the typical culprit behind <a href="https://doi.org/10.1016/B978-044451388-5/50020-5">coral bleaching in Ecuador</a>, but the excess heat from the hurricanes that we observed may contribute to stressed reefs and bleached coral far from where the storms appeared.</p>
<figure class="align-center ">
<img alt="Schools of striped tropical fish swim through a coral reef." src="https://images.theconversation.com/files/531242/original/file-20230611-26322-dj1p3x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/531242/original/file-20230611-26322-dj1p3x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=382&fit=crop&dpr=1 600w, https://images.theconversation.com/files/531242/original/file-20230611-26322-dj1p3x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=382&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/531242/original/file-20230611-26322-dj1p3x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=382&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/531242/original/file-20230611-26322-dj1p3x.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=480&fit=crop&dpr=1 754w, https://images.theconversation.com/files/531242/original/file-20230611-26322-dj1p3x.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=480&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/531242/original/file-20230611-26322-dj1p3x.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=480&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Coral reefs are essential habitat for fish and other sea life, but they are threatened by rising ocean temperatures.</span>
<span class="attribution"><a class="source" href="https://www.noaa.gov/education/resource-collections/marine-life/coral-reef-ecosystems">James Watt via NOAA</a></span>
</figcaption>
</figure>
<p>It is also possible that the excess heat from hurricanes stays within the ocean for decades or more without returning to the surface. This would actually have a mitigating impact on climate change. </p>
<p>As hurricanes redistribute heat from the ocean surface to greater depths, they can help to slow down warming of the Earth’s atmosphere by keeping the heat sequestered in the ocean. </p>
<p>Scientists have long thought of hurricanes as extreme events fueled by ocean heat and shaped by the Earth’s climate. <a href="https://doi.org/10.1073/pnas.2301664120">Our findings</a>, published in the Proceedings of the National Academy of Sciences, add a new dimension to this problem by showing that the interactions go both ways — hurricanes themselves have the ability to heat up the ocean and shape the Earth’s climate.</p><img src="https://counter.theconversation.com/content/206920/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Noel Gutiérrez Brizuela receives funding from the Mexican Council for Science and Technology (CONACYT). </span></em></p><p class="fine-print"><em><span>Sally Warner has received funding from the National Science Foundation and the Office of Naval Research.</span></em></p>Currents can carry that deep ocean heat hundreds of miles to surface again at distant shores.Noel Gutiérrez Brizuela, Ph.D. Candidate in Physical Oceanography, University of California, San DiegoSally Warner, Associate Professor of Climate Science, Brandeis UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/1968722022-12-20T04:34:03Z2022-12-20T04:34:03ZWhat is air turbulence?<figure><img src="https://images.theconversation.com/files/502061/original/file-20221220-18-124g72.jpg?ixlib=rb-1.1.0&rect=29%2C14%2C4882%2C3254&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">
</span> <span class="attribution"><a class="source" href="https://unsplash.com/photos/iiqpxCg2GD4">Philip Myrtorp / Unsplash</a></span></figcaption></figure><p>You probably know the feeling: you’re sitting on a plane, happily cruising through the sky, when suddenly the seat-belt light comes on and things get a little bumpy.</p>
<p>Most of the time, turbulence leads to nothing worse than momentary jitters or perhaps a spilled cup of coffee. In rare cases, passengers or flight attendants might end up with some injuries.</p>
<p>What’s going on here? Why are flights usually so stable, but sometimes get so unsteady?</p>
<p>As a meteorologist and atmospheric scientist who studies air turbulence, let me explain.</p>
<h2>What is air turbulence?</h2>
<p>Air turbulence is when the air starts to flow in a chaotic or random way. </p>
<p>At high altitudes the wind usually moves in a smooth, horizontal current called “laminar flow”. This provides ideal conditions for steady flight.</p>
<figure class="align-center ">
<img alt="A diagram showing laminar flow and turbulent flow." src="https://images.theconversation.com/files/502063/original/file-20221220-20-4bvy8f.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/502063/original/file-20221220-20-4bvy8f.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=376&fit=crop&dpr=1 600w, https://images.theconversation.com/files/502063/original/file-20221220-20-4bvy8f.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=376&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/502063/original/file-20221220-20-4bvy8f.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=376&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/502063/original/file-20221220-20-4bvy8f.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=472&fit=crop&dpr=1 754w, https://images.theconversation.com/files/502063/original/file-20221220-20-4bvy8f.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=472&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/502063/original/file-20221220-20-4bvy8f.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=472&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">In ‘laminar flow’, air moves smoothly in one direction. When turbulence begins, it goes every which way.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>Turbulence occurs when something disrupts this smooth flow, and the air starts to move up and down as well as horizontally. When this happens, conditions can change from moment to moment and place to place.</p>
<p>You can think of normal flying conditions as the glassy surface of the ocean on a still day. But when a wind comes up, things get choppy, or waves form and break – that’s turbulence.</p>
<h2>What causes air turbulence?</h2>
<p>The kind of turbulence that affects commercial passenger flights has three main causes.</p>
<p>The first is thunderstorms. Inside a thunderstorm, there is strong up-and-down air movement, which makes a lot of turbulence that can spread out to the surrounding region. Thunderstorms can also create “atmospheric waves”, which travel through the surrounding air and eventually break, causing turbulence. </p>
<p>Fortunately, pilots can usually see thunderstorms ahead (either with the naked eye or on radar) and will make efforts to go around them.</p>
<p>The other common causes of turbulence create what’s typically called “clear-air turbulence”. It comes out of air that looks perfectly clear, with no clouds, so it’s harder to dodge.</p>
<figure class="align-center ">
<img alt="A diagram showing mountains, air currents and turbulence." src="https://images.theconversation.com/files/502065/original/file-20221220-16-45aimu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/502065/original/file-20221220-16-45aimu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=464&fit=crop&dpr=1 600w, https://images.theconversation.com/files/502065/original/file-20221220-16-45aimu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=464&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/502065/original/file-20221220-16-45aimu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=464&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/502065/original/file-20221220-16-45aimu.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=583&fit=crop&dpr=1 754w, https://images.theconversation.com/files/502065/original/file-20221220-16-45aimu.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=583&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/502065/original/file-20221220-16-45aimu.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=583&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Jet streams and mountains are common causes of clear-air turbulence.</span>
<span class="attribution"><span class="source">Shutterstock</span></span>
</figcaption>
</figure>
<p>The second cause of turbulence is jet streams. These are high-speed winds in the upper atmosphere, at the kind of altitudes where passenger jets fly. </p>
<p>While air inside the jet stream moves quite smoothly, there is often turbulence near the top and bottom of the stream. That’s because there is a big difference in air speed (called “wind shear”) between the jet stream and the air outside it. High levels of wind shear create turbulence.</p>
<p>The third thing that makes turbulence is mountains. As air flows over a mountain range, it creates another kind of wave – called, of course, a “mountain wave” – that disrupts air flow and can create turbulence.</p>
<h2>Can air turbulence be avoided?</h2>
<p>Pilots do their best to avoid air turbulence – and they’re pretty good at it!</p>
<p>As mentioned, thunderstorms are the easiest to fly around. For clear-air turbulence, things are a little trickier.</p>
<p>When pilots encounter turbulence, they will change altitude to try to avoid it. They also report the turbulence to air traffic controllers, who pass the information on to other flights in the area so they can try to avoid it. </p>
<p>Weather forecasting centres also provide turbulence forecasts. Based on their models of what’s happening in the atmosphere, they can predict where and when clear-air turbulence is likely to occur.</p>
<h2>Will climate change make turbulence worse?</h2>
<p>As the globe warms and the climate changes in coming decades, we think air turbulence will also be affected.</p>
<p>One reason is that the jet streams which can cause turbulence are shifting and may become more intense. As Earth’s tropical climate zones spread away from the equator, the jet streams are moving with them.</p>
<p>This is likely to increase turbulence on at least some flight routes. Some studies also <a href="https://www.nature.com/articles/s41586-019-1465-z">suggest</a> the wind shear around jet streams has become more intense.</p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/could-climate-change-have-played-a-role-in-the-airasia-crash-36002">Could climate change have played a role in the AirAsia crash?</a>
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<p>Another reason is that the most severe thunderstorms are also likely to become more intense, partly because a warmer atmosphere can hold more water vapour. This too is likely to generate more intense turbulence.</p>
<p>These predictions are largely based on climate models, because it is difficult to collect the data needed to identify trends in air turbulence. These data largely come from reports by aircraft, the quality and extent of which are changing over time. These measurements are quite different from the long-term, methodically gathered data usually used to detect trends in the weather and climate.</p>
<h2>How dangerous is air turbulence?</h2>
<p>Around the globe, air turbulence causes hundreds of injuries each year among passengers and flight attendants on commercial aircraft. But, given the hundreds of millions of people who fly each year, those are pretty good odds.</p>
<p>Turbulence is usually short-lived. What’s more, modern aircraft are engineered to comfortably withstand all but the most extreme air turbulence. </p>
<p>And among people who are injured, the great majority are those who aren’t strapped in. So if you’re concerned, the easiest way to protect yourself is to wear your seat belt. </p>
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<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/heres-the-real-reason-to-turn-on-aeroplane-mode-when-you-fly-188585">Here's the real reason to turn on aeroplane mode when you fly</a>
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<img src="https://counter.theconversation.com/content/196872/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Todd Lane receives funding from the Australian Research Council.</span></em></p>When something disrupts the smooth, laminar flow of high-altitude winds, your flight might get a little bumpy.Todd Lane, Professor, School of Geography, Earth and Atmospheric Sciences, The University of Melbourne, The University of MelbourneLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/971712018-06-19T20:20:54Z2018-06-19T20:20:54ZTurbulence isn’t just a science problem<figure><img src="https://images.theconversation.com/files/221910/original/file-20180606-137312-13n1frf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">A crowd of people moving at different rates is a form of turbulence. </span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/view-drone-crowd-people-concert-760175308?src=y1sT8opK4GcahTI7fHuG4Q-1-17">from www.shutterstock.com </a></span></figcaption></figure><p><em><strong><a href="https://theconversation.com/au/topics/making-science-for-people-55106">Making science for people</a></strong> is a series that explores how humanities, arts and social sciences expertise is applied to problems typically corralled into the science and technology space. The first piece in the series is <a href="https://theconversation.com/creating-research-value-needs-more-than-just-science-arts-humanities-social-sciences-can-help-97083">here</a>.</em> </p>
<p><em>Today’s article takes a look at turbulence as a question of science – and of humanity.</em> </p>
<hr>
<p>Most of us have an understanding of what atmospheric turbulence is – nauseating plane movement is hard to forget. </p>
<p>But turbulence is all around us: not just in the air, but also in water, and even in crowds of moving people. </p>
<p>Perhaps surprisingly though, details around the science of turbulence are not all that well understood. Researchers studying flow and turbulence within different disciplines are yet to fully understand its complex operation – and as a result, solving problems related to turbulence is difficult. </p>
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<p>
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<strong>
Read more:
<a href="https://theconversation.com/explainer-how-dangerous-is-turbulence-and-can-it-bring-down-a-plane-59098">Explainer: how dangerous is turbulence ... and can it bring down a plane?</a>
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<h2>Turbulence all around us</h2>
<p>In a simple sense, turbulence can be described as a state of fluid flow. And although it makes some plane flights uncomfortable, turbulence in our atmosphere is essential to the existence of all life on earth. </p>
<p>Turbulence mixes heat, moisture, carbon dioxide and pollutants to and from the earth’s surface, maintaining our biosphere in a habitable state. Without turbulence, the air near the ground would be a lot hotter – when the sun is up, your feet would melt while your head would be freezing!</p>
<p>More than two-thirds of the Australian population <a href="http://www.abs.gov.au/ausstats/abs@.nsf/Lookup/by%20Subject/2071.0%7E2016%7EMain%20Features%7ESnapshot%20of%20Australia,%202016%7E2">live in capital cities</a>, creating problematic forms of turbulence. Highly populated regions with reduced vegetation cover absorb heat from the sun and release it through buoyant turbulent plumes. This process can create complex <a href="https://theconversation.com/walking-mightnt-be-good-for-you-if-its-through-australias-polluted-city-streets-88772">micro-climates with significant air quality issues</a>. </p>
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Read more:
<a href="https://theconversation.com/walking-mightnt-be-good-for-you-if-its-through-australias-polluted-city-streets-88772">Walking mightn't be good for you if it's through Australia's polluted city streets</a>
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<p>Smog and <a href="https://theconversation.com/are-toxic-algal-blooms-the-new-normal-for-australias-major-rivers-59526">algal blooms</a> are extreme circumstances where reduced levels of turbulence and flow affect us in a negative way. </p>
<figure class="align-center ">
<img alt="" src="https://images.theconversation.com/files/221094/original/file-20180531-69484-wljsgg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/221094/original/file-20180531-69484-wljsgg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=389&fit=crop&dpr=1 600w, https://images.theconversation.com/files/221094/original/file-20180531-69484-wljsgg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=389&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/221094/original/file-20180531-69484-wljsgg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=389&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/221094/original/file-20180531-69484-wljsgg.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=489&fit=crop&dpr=1 754w, https://images.theconversation.com/files/221094/original/file-20180531-69484-wljsgg.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=489&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/221094/original/file-20180531-69484-wljsgg.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=489&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Blue-green algae (or cyanobacteria) grows when water turbulence is low.</span>
<span class="attribution"><a class="source" href="http://www.scienceimage.csiro.au/tag/irrigation/i/4628/blue-green-algae-in-irrigation-drain/">Willem van Aken, CSIRO/ Wikimedia Commons</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>Turbulence in water <a href="https://www.youtube.com/watch?v=gU33NhsLG4k">certainly slows it down</a> – without turbulence, drifting in a canoe on the Yarra River would happen at a hair-raising 2,000 km per hour, instead of a lazy one km per hour.</p>
<p>In engineering terms, our inability to precisely model and control turbulent flows leads to inefficient over-design, and limits future technologies in a vast array of applications. About 10% of all the electricity generated every year is currently consumed in the process of <a href="https://www.bloomberg.com/view/articles/2018-01-29/this-physics-breakthrough-could-help-save-the-world">overcoming the effects of turbulence</a>.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/gU33NhsLG4k?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">Turbulence - it’s complicated.</span></figcaption>
</figure>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/are-toxic-algal-blooms-the-new-normal-for-australias-major-rivers-59526">Are toxic algal blooms the new normal for Australia's major rivers?</a>
</strong>
</em>
</p>
<hr>
<h2>Da Vinci’s ‘turbolenza’</h2>
<p>In the humanities disciplines, the notion of turbulence is widely employed in artistic representations and literary expressions right through to philosophical theories, economic modelling and descriptions of political revolution.</p>
<p>By contrast to their scientist counterparts, humanities scholars tend to use the concept of turbulence almost exclusively in a negative sense as disorder, disruption, agitation and commotion. </p>
<p>This sense of the word can be seen in one of the earliest documented considerations of flow patterns in water. Leonardo da Vinci, considering the whirling movement of water around an obstacle, described it as agitated and disrupted: as “turbolenza”. </p>
<p><a href="https://theconversation.com/why-leonardo-da-vinci-was-a-genius-54207">Da Vinci’s art and science</a> did not occur in a vacuum but was deeply shaped by the world around him. This was a world at war, which drove him across the Italian states and eventually to France. Some of his studies of air and water flow, and his inventions adapting bird flight, were directly intended as contributions towards military technologies in these conflicts. </p>
<p>Turbulence, therefore, was not just an abstract research subject for da Vinci but also a lived experience, and its design applications a critical source of income. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/why-leonardo-da-vinci-was-a-genius-54207">Why Leonardo da Vinci was a genius</a>
</strong>
</em>
</p>
<hr>
<p>Looking at Leonardo reminds us of the crucial but often ignored point that studies of turbulence have a long history. Understanding this history is fundamental to grasping how turbulence has been conceptualised in the past, which has informed how we understand it now, and how we will conceive of it in the future. </p>
<p>Such considerations are determined by the current problems of the day – be they technological, cultural, social and/or political. One of the most urgent issues of our time – and one which encapsulates turbulence in all of these facets – is the refugee crisis. This has created a flow of humans across lands in proportions historically unprecedented. </p>
<p>The use of chemical warfare on civilians in Syria also reflects the intersections between industrialisation, atmospheric turbulence and human flow. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/syrias-latest-chemical-massacre-demands-a-global-response-94668">Syria's latest chemical massacre demands a global response</a>
</strong>
</em>
</p>
<hr>
<h2>Solving problems with diverse expertise</h2>
<p>Understanding turbulence better may reduce drag, improve efficiency, lower fuel use and create better environmental outcomes when <a href="http://www.abc.net.au/catalyst/stories/3285559.htm">flying</a>. This is especially important to a country like Australia which relies so heavily on long-haul air travel. </p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/_w6OnK-Djns?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">How turbulence affects planes.</span></figcaption>
</figure>
<p>Or, by establishing reliable and validated models for the magnitudes and scales of turbulence on wind and tidal energy farms, we could improve their reliability, and reduce risks associated with <a href="https://www.windpowerengineering.com/design/how-turbulent-wind-abuse-wind-turbine-drivetrains/">turbine failure and loss of power supply</a>. </p>
<p>Understanding turbulence in coastal and inland waters will assist in identifying best practice maintenance of riverine, estuarine and coastal ocean health.</p>
<p>In the longer term, engineering capability regarding turbulence from may help us understand turbulent flow of people, for example following the use of chemical weapons in war and in refugee crises. </p>
<p>Partnerships across science, technology, engineering, arts and humanities help us consider how and why turbulence is understood in different cultural knowledge systems, and understand how turbulent flows in everyday and extreme contexts are understood, modelled, and managed.</p>
<p>That is how we can build a sustainable future. </p>
<hr>
<p>
<em>
<strong>
Read more:
<a href="https://theconversation.com/creating-research-value-needs-more-than-just-science-arts-humanities-social-sciences-can-help-97083">Creating research value needs more than just science – arts, humanities, social sciences can help</a>
</strong>
</em>
</p>
<hr>
<img src="https://counter.theconversation.com/content/97171/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Ivan Marusic receives funding from the Australian Research Council</span></em></p><p class="fine-print"><em><span>Joy Damousi receives funding from the Australian Research Council </span></em></p><p class="fine-print"><em><span>Susan Broomhall receives funding from the Australian Research Council.</span></em></p>You might be familiar with turbulence as you experience it on a plane, or as scholars describe combustible forces of social change. But understanding how it operates is far more complex.Ivan Marusic, Professor of Mechanical Engineering, The University of MelbourneJoy Damousi, Professor of History, The University of MelbourneSusan Broomhall, Professor of History, The University of Western AustraliaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/806362017-08-08T00:57:14Z2017-08-08T00:57:14ZScientist at work: Why this meteorologist is eager for an eclipse<figure><img src="https://images.theconversation.com/files/181075/original/file-20170804-27483-1h1khg2.jpg?ixlib=rb-1.1.0&rect=209%2C0%2C1622%2C1072&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">Hiscox and students practice for the big day with a weather balloon.</span> <span class="attribution"><span class="source">Joshua Burrack</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span></figcaption></figure><p>By all accounts a total solar eclipse is a life-changing event. I wouldn’t know, I’ve never seen one. Fortunately for me and millions across the U.S., that will change this summer.</p>
<p>I’m not really an eclipse expert, even though I can’t wait for August 21. I’m actually a meteorologist, and a fairly specialized one at that. Six months ago, I didn’t know the difference between an umbra and penumbra. What I did know is that the sun provides energy for everything that happens on our planet, and that the daily cycle of sun rising and setting is a key component of what happens in the atmosphere, and how air circulates locally and globally. </p>
<p>So why is someone who worries about subsecond- and submeter-scale winds interested in this astronomical-scale event? Because any change in incoming sun – such as the complete blackout during a total solar eclipse – will affect the energy received by the land, and in turn the energy transferred back to the atmosphere. And because the total eclipse period is short, those changes will be small. It’s both an exciting event and an interesting challenge: a scientist’s dream.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/181116/original/file-20170806-10088-1o0whzd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/181116/original/file-20170806-10088-1o0whzd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/181116/original/file-20170806-10088-1o0whzd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=408&fit=crop&dpr=1 600w, https://images.theconversation.com/files/181116/original/file-20170806-10088-1o0whzd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=408&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/181116/original/file-20170806-10088-1o0whzd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=408&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/181116/original/file-20170806-10088-1o0whzd.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=513&fit=crop&dpr=1 754w, https://images.theconversation.com/files/181116/original/file-20170806-10088-1o0whzd.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=513&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/181116/original/file-20170806-10088-1o0whzd.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=513&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The mini-night caused by the moon blacking out the sun during the day is an opportunity to investigate many scientific questions.</span>
<span class="attribution"><a class="source" href="http://www.apimages.com/metadata/Index/Russia-Europe-Solar-Eclipse/44d1094c93774d39a3324d19adb5efee/1/0">AP Photo/Dmitry Lovetsky</a></span>
</figcaption>
</figure>
<p>Coupled with advances in observational techniques, every eclipse offers a new chance to prove meteorological theories. This one even more so because coordination across the entire length of the continental United States almost guarantees that someone will have ideal observing conditions. We’re prepping our weather balloons and weather stations to take advantage of that opportunity – to see exactly what a short blackout does to atmospheric motion.</p>
<h2>Meteorology all goes back to the sun</h2>
<p>From how <a href="https://www.epa.gov/ozone-pollution">pollutants are formed and transported</a>, to how plants exchange carbon using photosynthesis, to what direction the wind blows, daytime processes are <a href="https://doi.org/10.1175/JAS3654.1">different from nighttime processes</a>. Without energy input from the sun, the lower atmosphere slowly flips itself at night. </p>
<p>During the day, it’s warm near the ground and cooler up above; at night it’s just the opposite. This “stable” (warmer over cooler) air inhibits vertical motion of the air and anything suspended in it. So <a href="https://doi.org/10.1191/0309133305pp442ra">pollutants can stay closer to the ground</a>, <a href="https://doi.org/10.1175/1520-0469(2001)058%3C1409:FADONB%3E2.0.CO;2">clouds form differently</a>, <a href="https://doi.org/10.1175/1520-0469(1967)024%3C0029:KWITEA%3E2.0.CO;2">air flows faster down valleys</a> and at the coasts <a href="http://www.srh.noaa.gov/jetstream/ocean/seabreeze.html">wind blows offshore instead of on</a>. </p>
<p>While those generalities are known, the nuances and timings aren’t fully understood, and thus they are not completely predictable. That’s my sphere of science – turbulence. I’m interested in the atmospheric changes in short times and small spaces that can eventually influence the larger “weather” most people are familiar with.</p>
<p>The total solar eclipse is a mini-night experience, so we will use it as a natural experiment. Is a brief period without solar radiation enough to cause detectable changes in turbulence and stability, or is it the slower interactions of land and atmosphere over a whole night that are required? We’ll take what we find and use it to think about normal non-eclipse conditions.</p>
<h2>Head in the sky</h2>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/181066/original/file-20170804-6948-1y2u1lq.gif?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/181066/original/file-20170804-6948-1y2u1lq.gif?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/181066/original/file-20170804-6948-1y2u1lq.gif?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=329&fit=crop&dpr=1 600w, https://images.theconversation.com/files/181066/original/file-20170804-6948-1y2u1lq.gif?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=329&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/181066/original/file-20170804-6948-1y2u1lq.gif?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=329&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/181066/original/file-20170804-6948-1y2u1lq.gif?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=413&fit=crop&dpr=1 754w, https://images.theconversation.com/files/181066/original/file-20170804-6948-1y2u1lq.gif?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=413&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/181066/original/file-20170804-6948-1y2u1lq.gif?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=413&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The troposphere is the part of the atmosphere closest to Earth’s surface and includes the air we breathe.</span>
<span class="attribution"><a class="source" href="https://www.giss.nasa.gov/research/features/201210_shindell/">NASA ESPO/INTEX-NA Educational Outreach</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>By launching a series of weather balloons before, during and after the eclipse we will see the evolution of winds and temperatures above the Earth’s surface over time. The instrument packages attached to the balloons take measurements from about 100 meters above the surface up through the lower atmosphere, troposphere and lower stratosphere, eventually reaching nearly 20 kilometers. Scientists are coordinating all across the eclipse’s path, and will conduct this same experiment at <a href="http://eclipse.montana.edu/">several sites</a> across the country.</p>
<p>At our site in South Carolina, we are focusing on the question of whether a total eclipse can generate internal atmospheric <a href="http://glossary.ametsoc.org/wiki/Gravity_wave">gravity waves</a>: parcels of air moving together as chunks trying to regain an equilibrium in temperature and density. (These are different from the <a href="https://theconversation.com/gravitational-waves-discovered-top-scientists-respond-53956">gravitational waves</a> that result when black holes collide.) Sometimes gravity waves are visible in clouds. During previous eclipses <a href="https://doi.org/10.1098/rsta.2015.0222">there has been promising evidence</a> of gravity wave activity, but not enough data from enough locations to fully understand them.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/181044/original/file-20170804-10658-igira4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/181044/original/file-20170804-10658-igira4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/181044/original/file-20170804-10658-igira4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=462&fit=crop&dpr=1 600w, https://images.theconversation.com/files/181044/original/file-20170804-10658-igira4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=462&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/181044/original/file-20170804-10658-igira4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=462&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/181044/original/file-20170804-10658-igira4.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=580&fit=crop&dpr=1 754w, https://images.theconversation.com/files/181044/original/file-20170804-10658-igira4.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=580&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/181044/original/file-20170804-10658-igira4.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=580&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The pattern of atmospheric gravity waves is visible in this satellite image of double, overlapping arcs of clouds over the Indian Ocean.</span>
<span class="attribution"><a class="source" href="https://visibleearth.nasa.gov/view.php?id=69463">Jacques Descloitres, MODIS Rapid Response Team, NASA/GSFC</a>, <a class="license" href="http://creativecommons.org/licenses/by/4.0/">CC BY</a></span>
</figcaption>
</figure>
<p>The vertical profiles of temperature, relative humidity, wind speed and wind direction we collect will be used to answer a number of other scientific questions as well. First, we’ll add to the sparse database of eclipse-induced temperature changes and provide quantitative measures of how strong the temperature change is and how long the lag between the total blackness at solar minimum and the temperature minimum is.</p>
<p>We will also be able to see if the cooling when the sun disappears and sudden rewarming when it returns propagates vertically and, if so, how far above the Earth’s surface it goes. In terms of wind, questions to be answered center around changes in wind speed and turbulence intensity. We believe we will see a reduction of both, which provides further explanation for the eerie “<a href="https://phys.org/news/2016-08-mystery-eclipse-years.html">eclipse wind</a>” so often cited by human observers.</p>
<p>This more comprehensive examination of the troposphere and stratosphere in time and space will help inform our modeling and prediction of regional weather and climate.</p>
<h2>Feet on the ground</h2>
<p>But what if the changes are smaller? A helium-filled balloon leaves the ground quickly – ideally at five meters per second – and the first reliable measurement is almost 100 meters above the ground. A lot can happen in 100 meters.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/181067/original/file-20170804-2386-s32kso.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/181067/original/file-20170804-2386-s32kso.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/181067/original/file-20170804-2386-s32kso.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/181067/original/file-20170804-2386-s32kso.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/181067/original/file-20170804-2386-s32kso.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/181067/original/file-20170804-2386-s32kso.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/181067/original/file-20170804-2386-s32kso.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/181067/original/file-20170804-2386-s32kso.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Postdoc Alexandria McCombs and graduate students Mayra Roman-Rivera and Peter Tereskiewicz work on installing meteorological instruments in preparation for the eclipse experiment.</span>
<span class="attribution"><span class="source">Ian Giammanco, Insurance Institute for Business & Home Safety,DisasterSafety.org</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>To fill in that gap, at our site in South Carolina, we are adding other measurements. We’ve erected a small tower with fine thermocouples every half-meter from the ground up. These thin wires can detect temperature changes over 0.1-second time periods and will help us see if the darkness causes a very shallow layer of cooler air to start to grow under the typical daytime warmth. </p>
<p>The tower will also house two sonic anemometers – sensors that use disruption in a sound pulse to measure the wind speed in three dimensions at very fast rates – to see if a <a href="http://glossary.ametsoc.org/wiki/Wind_shear">wind shear</a> develops near ground level.</p>
<p>An infrared gas analyzer will record carbon fluxes throughout the eclipse period to see if there is any detectable change in plant respiration. Remember, they “breathe” in carbon dioxide. <a href="http://sciencing.com/animals-reaction-solar-eclipse-3503.html">Some animals interpret an eclipse as night</a> – do the plants?</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/181069/original/file-20170804-2386-e2v3uh.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/181069/original/file-20170804-2386-e2v3uh.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/181069/original/file-20170804-2386-e2v3uh.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=400&fit=crop&dpr=1 600w, https://images.theconversation.com/files/181069/original/file-20170804-2386-e2v3uh.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=400&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/181069/original/file-20170804-2386-e2v3uh.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=400&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/181069/original/file-20170804-2386-e2v3uh.JPG?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=503&fit=crop&dpr=1 754w, https://images.theconversation.com/files/181069/original/file-20170804-2386-e2v3uh.JPG?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=503&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/181069/original/file-20170804-2386-e2v3uh.JPG?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=503&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">The USC backscatter lidar at a recent field deployment in New Zealand.</span>
<span class="attribution"><span class="source">April Hiscox</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>Finally, we’ll also deploy a lidar system. That’s like a radar, but with a laser that will point upward. This is to see if there are any changes in the depth of the boundary layer – a transition point between where the atmosphere is affected by the Earth’s surface to the free troposphere above.</p>
<p>And we’re going to do all of this in just two minutes and 36 seconds. A tiny window for a big impact.</p>
<figure class="align-center zoomable">
<a href="https://images.theconversation.com/files/181070/original/file-20170804-7490-3b1kae.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/181070/original/file-20170804-7490-3b1kae.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&fit=clip" srcset="https://images.theconversation.com/files/181070/original/file-20170804-7490-3b1kae.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=338&fit=crop&dpr=1 600w, https://images.theconversation.com/files/181070/original/file-20170804-7490-3b1kae.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=338&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/181070/original/file-20170804-7490-3b1kae.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=338&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/181070/original/file-20170804-7490-3b1kae.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=424&fit=crop&dpr=1 754w, https://images.theconversation.com/files/181070/original/file-20170804-7490-3b1kae.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=424&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/181070/original/file-20170804-7490-3b1kae.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=424&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">A practice weather balloon soars above the USC campus.</span>
<span class="attribution"><span class="source">Patrick Remson</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<h2>Collating the data to flesh out the theory</h2>
<p>A total solar eclipse is often referred to as a meteorological playground, and that is just how it feels. We’re taking out all our scientific toys to see what we can find. Eclipse events are relatively rare; meteorologists like me take what we know about the interactions between land and air to think logically about what will happen during an eclipse. But until we see it, put an equation on it and predict the next one, it still falls into the realm of theory, not reliably predictable weather. </p>
<p>I feel like a kid again – the eclipse has forced me to think about meteorology in a new and different way – just like looking at the world while hanging upside down from monkey bars.</p><img src="https://counter.theconversation.com/content/80636/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>April Hiscox receives funding for eclipse related research from South Carolina Space Grant and The University of South Carolina Office of Research. </span></em></p>Meteorology researchers across the country are prepping experiments for the mini-night the eclipse will bring on August 21 – two minutes and 36 seconds without the sun in the middle of the day.April Hiscox, Associate Professor of Geography, University of South CarolinaLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/807952017-08-03T00:59:51Z2017-08-03T00:59:51ZHow hot weather – and climate change – affect airline flights<figure><img src="https://images.theconversation.com/files/180077/original/file-20170727-8486-3gcmgf.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">When is it too hot to fly?</span> <span class="attribution"><a class="source" href="https://www.shutterstock.com/image-photo/heat-wave-airplane-airport-665107561">Dmitri Fedorov/Shutterstock.com</a></span></figcaption></figure><p>Hot weather has forced <a href="https://www.washingtonpost.com/news/capital-weather-gang/wp/2017/06/20/its-so-hot-in-phoenix-that-airplanes-cant-fly/">dozens of commercial flights to be canceled</a> at airports in the Southwest this summer. This flight-disrupting heat is a warning sign. Climate change is projected to have far-reaching repercussions – including <a href="http://dx.doi.org/10.1098/rsta.2012.0294">sea level rise inundating cities</a> and shifting weather patterns causing <a href="http://dx.doi.org/10.1073/pnas.0906865106">long-term declines in agricultural yields</a>. And there is evidence that it is beginning to affect the takeoff performance of commercial aircraft, with potential effects on airline costs.</p>
<p>National and global transportation systems and the economic activity they support have been <a href="http://dx.doi.org/10.1038/nature15725">optimized for the climate</a> in which it all developed: Machines are designed to operate in common temperature ranges, logistical plans depend on historical weather patterns and coastal land development is based on <a href="http://cpo.noaa.gov/sites/cpo/Reports/2012/NOAA_SLR_r3.pdf">known flood zones</a>. In the aviation sector, airports and aircraft are designed for the weather conditions experienced historically. Because the climate is changing, even fundamental infrastructure elements like airports and key economic sectors like air transportation may need to be redesigned and reengineered.</p>
<p>As scientists focused on the <a href="http://dx.doi.org/10.1175/WCAS-D-15-0063.1">impacts of climate change and extreme weather</a> on human society and natural ecosystems around the world, our research has quantified how extreme heat associated with our <a href="http://dx.doi.org/10.1007/s10584-017-2018-9">warming climate may affect flights</a> around the world. We’ve found that major airports from New York to Dubai to Bangkok will see more frequent takeoff weight restrictions in the coming decades due to increasingly common hot temperatures.</p>
<h2>Climate changes flights</h2>
<p>There is robust evidence that extreme events such as heat waves and coastal flooding are happening with <a href="http://dx.doi.org/10.1073/pnas.1222469111">greater frequency and intensity</a> than just a few decades ago. And if we fail to reduce greenhouse gas emissions significantly in the next few decades, the frequency and intensity of these extremes is projected to <a href="http://dx.doi.org/10.1002/jgrd.50188">increase dramatically</a>. </p>
<p>The effects on aviation may be widespread. Many airports are built near sea level, putting them <a href="https://doi.org/10.1016/j.trpro.2016.05.036">at risk of more frequent flooding</a> as oceans rise. The frequency and intensity of <a href="http://dx.doi.org/10.1038/nclimate1866">air turbulence may increase</a> in some regions due to <a href="http://dx.doi.org/10.1007/s00376-017-6268-2">strengthening high-altitude winds</a>. Stronger winds would force airlines and pilots to <a href="https://doi.org/10.1088/1748-9326/11/2/024008">modify flight lengths and routings</a>, potentially increasing fuel consumption. </p>
<p>The July heat-related <a href="https://www.circa.com/story/2017/06/20/nation/american-airlines-canceled-flights-in-phoenix-because-its-too-hot-for-planes-to-fly">Phoenix flight cancellations</a> happened at least in part because airlines’ operational manuals didn’t include information for <a href="http://www.fox10phoenix.com/news/arizona-news/262509476-story">temperatures above 118 degrees Fahrenheit</a> – because that kind of heat is historically uncommon. It’s another example of how procedures may need to be updated to adapt to a warmer climate.</p>
<h2>Flying in the heat</h2>
<p>High air temperatures affect the physics of how aircraft fly, meaning aircraft takeoff performance can be <a href="https://doi.org/10.1175/WCAS-D-14-00026.1">impaired on hot days</a>. The amount of lift that an airplane wing generates is affected by the density of the air. Air density in turn depends mostly on air temperature and elevation; higher temperatures and higher elevations both reduce density. </p>
<figure class="align-right zoomable">
<a href="https://images.theconversation.com/files/179073/original/file-20170720-1588-51jqbs.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=1000&fit=clip"><img alt="" src="https://images.theconversation.com/files/179073/original/file-20170720-1588-51jqbs.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/179073/original/file-20170720-1588-51jqbs.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=874&fit=crop&dpr=1 600w, https://images.theconversation.com/files/179073/original/file-20170720-1588-51jqbs.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=874&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/179073/original/file-20170720-1588-51jqbs.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=874&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/179073/original/file-20170720-1588-51jqbs.jpeg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=1098&fit=crop&dpr=1 754w, https://images.theconversation.com/files/179073/original/file-20170720-1588-51jqbs.jpeg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=1098&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/179073/original/file-20170720-1588-51jqbs.jpeg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=1098&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px"></a>
<figcaption>
<span class="caption">Hot air is less dense than cooler air. That affects the amount of lift an airplane can generate.</span>
<span class="attribution"><span class="source">The Conversation (via Piktochart)</span>, <a class="license" href="http://creativecommons.org/licenses/by-nd/4.0/">CC BY-ND</a></span>
</figcaption>
</figure>
<p>The lower the air density, the faster an airplane must travel to produce enough lift to take off. It takes more runway to reach a higher speed, and depending on how long the airport’s runway is, some airplanes might risk running out of room before reaching sufficient speed. When this occurs, the only immediate option is to reduce the aircraft’s weight to lower its required takeoff speed – by removing passengers, luggage and cargo. This is referred to as a weight restriction. </p>
<p>Weight restrictions happen now, especially in hot places like Phoenix and <a href="http://www.ldeo.columbia.edu/news-events/surging-heat-may-limit-aircraft-takeoffs-globally">Dubai</a> and at airports with short runways like <a href="https://www.wsj.com/articles/la-guardias-runways-come-up-short-1479078957">New York’s LaGuardia</a> and Washington, D.C.’s Reagan National, but our research suggests that they may become much more common in the future. </p>
<p>Global temperatures have been <a href="https://www.ipcc.ch/report/ar5/wg1/">steadily rising for decades</a>, and they will almost certainly continue to do so. In some regions, there is evidence that the <a href="http://dx.doi.org/10.1002/2015GL064914">hottest temperatures may increase at a faster rate</a> than the average, <a href="http://dx.doi.org/10.1007/s40641-016-0042-x">further stacking the deck</a> in favor of extreme heat. These hotter temperatures will reduce air density and make it much more likely weight restrictions are needed for flights taking off during the hottest parts of the day. </p>
<p>The frequency and magnitude of weight restrictions is projected to increase – in some locations, the number of days requiring at least some amount of weight restriction for certain aircraft could double or triple, perhaps covering 50 or more days per year.</p>
<h2>The economics of adaptation</h2>
<p>On most affected flights, the amount of cargo, passengers and fuel that must be removed to allow for takeoff will usually be small – between 0.5 percent and 4 percent of the total load. That means fewer paying customers on airplanes, and less cargo on board. When those restrictions add up across the global air transport system, the costs can be significant.</p>
<p>Carrying just a fraction of a percent fewer passengers or less cargo can add up to <a href="https://www.wired.com/2012/09/how-can-airlines-reduce-fuel-costs/">millions of dollars in lost revenue</a> for an airline over years of operation. That makes even small weight restrictions a concern in such a highly competitive and optimized industry. These limits could disproportionately affect <a href="https://www.ft.com/content/689a1618-814d-11e5-8095-ed1a37d1e096">long-haul flights</a>, which require large fuel loads and often take off near their maximum weights.</p>
<p>There are ways that airlines could mitigate increasing weight restrictions. The most feasible is to reschedule some flights to cooler hours of the day – although with <a href="http://www.iata.org/pressroom/pr/Pages/2016-10-18-02.aspx">air traffic increasing</a> and many airports already <a href="http://www.accessmagazine.org/spring-2016/manage-flight-demand-or-build-airport-capacity/">operating near capacity</a>, this could prove difficult. </p>
<p>Another potential solution is to build longer runways. But that’s not always possible: Some airports, like New York’s LaGuardia, are on coastlines or in dense urban environments. Even where a longer runway is technically possible, buying the land and expanding an airport’s physical area may be <a href="http://www.bbc.com/news/business-35011620">expensive and politically difficult</a>.</p>
<p>Aircraft could be optimized for takeoff performance, but redesigning aircraft is <a href="http://www.seattletimes.com/business/boeing-aerospace/will-787-program-ever-show-an-overall-profit-analysts-grow-more-skeptical/">extremely expensive and can take decades</a>. <a href="http://www.boeing.com/features/2016/01/innovation-777-lighter-01-16.page">Manufacturers are always working</a> to build planes that are <a href="https://www.wired.com/2015/06/planes-get-efficient-heres/">lighter and more fuel-efficient</a>. In the future, those efficiency improvements will be necessary just to maintain today’s performance.</p>
<h2>Broader implications</h2>
<p>These changes are merely examples of the countless procedures, processes and equipment requirements that will have to be adjusted for a changing climate. Even if those adaptations are successful, they will take effort and money to achieve.</p>
<p>Many sectors of the economy, including the aviation industry, have yet to seriously consider the effects of climate change. The sooner, the better: Both airport construction and aircraft design take decades, and have lasting effects. Today’s newest planes may well be <a href="http://www.airspacemag.com/need-to-know/what-determines-an-airplanes-lifespan-29533465/">flying in 40 or 50 years</a>, and their replacements are being designed now. The earlier climate impacts are understood and appreciated, the more effective and less costly adaptations can be. Those adaptations may even include innovative ways to dramatically reduce climate-altering emissions across the aviation sector, which would help reduce the problem while also responding to it.</p><img src="https://counter.theconversation.com/content/80795/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>The authors do not work for, consult, own shares in or receive funding from any company or organization that would benefit from this article, and have disclosed no relevant affiliations beyond their academic appointment.</span></em></p>Major airports around the world will see more frequent flight restrictions in the coming decades because of increasingly common hot temperatures.Ethan D. Coffel, Ph.D. Student in Earth & Environmental Sciences, Columbia UniversityRadley Horton, Associate Research Scientist, Center for Climate Systems Research, Columbia UniversityLicensed as Creative Commons – attribution, no derivatives.tag:theconversation.com,2011:article/590982016-05-12T08:53:50Z2016-05-12T08:53:50ZExplainer: how dangerous is turbulence … and can it bring down a plane?<figure><img src="https://images.theconversation.com/files/121703/original/image-20160509-20616-syu0so.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=496&fit=clip" /><figcaption><span class="caption">There may be trouble ahead.</span> <span class="attribution"><a class="source" href="http://www.shutterstock.com/dl2_lim.mhtml?src=pp-same_artist-185886419-m8tFG1MIdSfhTTe7ygCZfw-1&clicksrc=download_btn_inline&id=210086296&size=medium_jpg&submit_jpg=">Shutterstock</a></span></figcaption></figure><p>If you have ever travelled on an aeroplane the chances are you have experienced some form of turbulence. For those of us who fly infrequently, it can be alarming and unnerving, but rest assured that for the pilots and crew who experience turbulence every day, it is business as usual.</p>
<p>You will normally receive a message to return to your seats and fasten your seat belts as the biggest risk is passenger injury as the aircraft is jostled about. </p>
<p>But is it always so innocent? Earlier this month, more than 30 passengers were reportedly injured when an <a href="http://www.bbc.co.uk/news/world-36209833">Etihad A330-200 airliner flew through “severe” turbulence over Indonesia</a>. The plane landed safely, but could similar conditions trigger an even worse accident – or even destroy an aircraft?</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/NWpRc07X_AU?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The Indonesian incident caught on camera.</span></figcaption>
</figure>
<p>In fact, aircraft are engineered to take a remarkable amount of stresses and strains, and a huge safety margin is built into the designs so that even very severe turbulence will not exceed the design limits of the aircraft. For example, the level of turbulence required to bend a wing spar is something even most pilots will not experience in a lifetime of travelling. </p>
<p>Wings are designed to withstand a load 1.5 times that which they would usually experience in flight. That means the wing tips are flexed up to 90 degrees <a href="http://www.bbc.com/future/story/20140319-stress-tests-for-safer-planes">during testing</a>. The flexing and bending of a wing in flight is intended by design, and a very rigid wing would break much more easily. Skyscrapers are also designed this way, to <a href="http://www.livescience.com/10532-skyscraper-sways-grass-wind.html">actually sway a little</a> – it makes them far more robust.</p>
<h2>What is turbulence?</h2>
<p>In its most simple sense, <a href="http://www.turbulenceforecast.com/atlantic.php">turbulence</a> is a disturbance in the air, and is not unlike the movement of waves and sea currents. If there are no obstacles in the way of an incoming wave it will “flow” nicely, but if it hits a sea wall, say, it will break up and you can see the disruption to the wave. As air flows over man-made structures and natural terrain such as mountains, the air flow is disrupted and causes the air above and around it to become turbulent. So if you take off or land from an airport close to a mountain range or very hilly terrain you are more likely to experience this kind of turbulence during and shortly after take-off.</p>
<p>Turbulence at higher altitudes is more likely caused by weather conditions creating pressure differentials which again disrupt the air flow. Often the term “air pocket” is used to explain this to passengers but these are not really pockets of air – the aircraft is in fact following the direction of the turbulent air which may be up or down or side to side. It often causes a quick drop in altitude which you feel by being lifted from your seat, or even a climb which presses you into your seat. When you are seated inside the aircraft cabin these movements feel amplified and you may feel like the aircraft has moved much more than it actually has.</p>
<p>Turbulence is usually described using qualitative measures such as <a href="http://maps.avnwx.com/help/turb_desc.html">“light”, “moderate”, “severe” and “extreme”</a>. In very extreme conditions and very certain scenarios, it can lead to accidents but it should be noted that these conditions are very rare. One method that is often used for analysing aircraft accidents is called the “Swiss cheese model”.</p>
<figure>
<iframe width="440" height="260" src="https://www.youtube.com/embed/QdLZFiUonPk?wmode=transparent&start=0" frameborder="0" allowfullscreen=""></iframe>
<figcaption><span class="caption">The Swiss cheese model made simple.</span></figcaption>
</figure>
<p>In the model, slices of Swiss cheese are stacked up, and each slice represents a defence that is put in place to prevent an accident happening. The slices have holes in them which represent weaknesses in the defence, and when all the holes line up, an accident occurs. So an accident can occur when the holes line up, but also if a slice is missing entirely (no defence in place). When we apply this model to an example of how turbulence has resulted in an aircraft crash, we can see some obvious holes or slices missing. </p>
<h2>When things do go wrong</h2>
<p>Sadly, human error and turbulence together can lead to fatalities. In 1966, a Boeing 707 was <a href="http://news.bbc.co.uk/onthisday/hi/dates/stories/march/5/newsid_2515000/2515321.stm">brought down by turbulence</a> when the pilot had diverted from his planned flight path out of Tokyo to show his passengers Mount Fuji. The 140 mph wind off the mountain ripped the tail to pieces and the aircraft crashed, killing everyone aboard. </p>
<p>To prevent this kind of turbulence from causing an accident, one of our “Swiss cheese” layers is the routine task of flight planning. Pilots are trained to understand risks and causes of turbulence, and aircraft routes are designed to minimise these risks. By changing the flight plan during flight, the pilot effectively removed a Swiss cheese layer – that which minimised the probability of flying into turbulence and exposing the aircraft to risk. </p>
<figure class="align-left ">
<img alt="" src="https://images.theconversation.com/files/122115/original/image-20160511-18140-15o2ydj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=237&fit=clip" srcset="https://images.theconversation.com/files/122115/original/image-20160511-18140-15o2ydj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=600&h=451&fit=crop&dpr=1 600w, https://images.theconversation.com/files/122115/original/image-20160511-18140-15o2ydj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=600&h=451&fit=crop&dpr=2 1200w, https://images.theconversation.com/files/122115/original/image-20160511-18140-15o2ydj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=600&h=451&fit=crop&dpr=3 1800w, https://images.theconversation.com/files/122115/original/image-20160511-18140-15o2ydj.jpg?ixlib=rb-1.1.0&q=45&auto=format&w=754&h=567&fit=crop&dpr=1 754w, https://images.theconversation.com/files/122115/original/image-20160511-18140-15o2ydj.jpg?ixlib=rb-1.1.0&q=30&auto=format&w=754&h=567&fit=crop&dpr=2 1508w, https://images.theconversation.com/files/122115/original/image-20160511-18140-15o2ydj.jpg?ixlib=rb-1.1.0&q=15&auto=format&w=754&h=567&fit=crop&dpr=3 2262w" sizes="(min-width: 1466px) 754px, (max-width: 599px) 100vw, (min-width: 600px) 600px, 237px">
<figcaption>
<span class="caption">Too many holes and you can expect an accident.</span>
<span class="attribution"><a class="source" href="http://www.shutterstock.com/dl2_lim.mhtml?src=KE1oOPru5LKTdKr9_OwseQ-1-0&clicksrc=download_btn_inline&id=253185553&size=medium_jpg&submit_jpg=">Shutterstock</a></span>
</figcaption>
</figure>
<p>In the Mount Fuji case, a second layer of Swiss cheese had a hole in it, too – the aircraft design itself, which had known stress limits and weaknesses. The <a href="http://aviation-safety.net/database/record.php?id=19660305-1">accident report stated</a>: “The aircraft suddenly encountered abnormally severe turbulence over Gotemba City which imposed a gust load considerably in excess of the design limit.” (Note that modern aircraft are designed to higher standards of stress and strain resilience and would probably have not been brought down if a similar situation arose today).</p>
<p>Pilots tend to report incidents of turbulence and aircraft sometimes radio ahead to ask if any has been experienced. It can begin very quickly which is why you are advised to keep your seat belts fastened when flying. But rest assured, modern aircraft are extremely tough and have been designed to endure severe turbulence – you might spill your drink though.</p><img src="https://counter.theconversation.com/content/59098/count.gif" alt="The Conversation" width="1" height="1" />
<p class="fine-print"><em><span>Darren Ansell does not work for, consult, own shares in or receive funding from any company or organisation that would benefit from this article, and has disclosed no relevant affiliations beyond their academic appointment.</span></em></p>It’s all to do with the ‘Swiss cheese model’.Darren Ansell, Space and Aerospace Engineering Lead, University of Central LancashireLicensed as Creative Commons – attribution, no derivatives.