{"id":4718,"date":"2015-06-17T06:18:55","date_gmt":"2015-06-17T06:18:55","guid":{"rendered":"http:\/\/revoscience.com\/en\/?p=4718"},"modified":"2015-06-17T06:18:55","modified_gmt":"2015-06-17T06:18:55","slug":"small-thunderstorms-may-add-up-to-massive-cyclones-on-saturn","status":"publish","type":"post","link":"https:\/\/www.revoscience.com\/en\/small-thunderstorms-may-add-up-to-massive-cyclones-on-saturn\/","title":{"rendered":"Small thunderstorms may add up to massive cyclones on Saturn"},"content":{"rendered":"

New model may predict cyclone activity on other planets.<\/strong><\/em><\/span><\/p>\n

\"Saturn's<\/a>
Saturn’s north polar vortex.
Image courtesy of Caltech\/Space Science Institute<\/figcaption><\/figure>\n

CAMBRIDGE, Mass<\/strong>—\u00a0For the last decade, astronomers have observed curious \u201chotspots\u201d on Saturn\u2019s poles. In 2008, NASA\u2019s Cassini spacecraft beamed back close-up images of these hotspots, revealing them to be immense cyclones, each as wide as the Earth. Scientists estimate that Saturn\u2019s cyclones may whip up 300 mph winds, and likely have been churning for years.<\/span><\/p>\n

While cyclones on Earth are fueled by the heat and moisture of the oceans, no such bodies of water exist on Saturn. What, then, could be causing such powerful, long-lasting storms?<\/span><\/p>\n

In a paper published today in the journal\u00a0Nature Geoscience,<\/em>\u00a0atmospheric scientists at MIT propose a possible mechanism for Saturn\u2019s polar cyclones: Over time, small, short-lived thunderstorms across the planet may build up angular momentum, or spin, within the atmosphere \u2014 ultimately stirring up a massive and long-lasting vortex at the poles.<\/span><\/p>\n

The researchers developed a simple model of Saturn\u2019s atmosphere, and simulated the effect of multiple small thunderstorms forming across the planet over time. Eventually, they observed that each thunderstorm essentially pulls air towards the poles \u2014\u00a0and together, these many small, isolated thunderstorms can accumulate enough atmospheric energy at the poles to generate a much larger and long-lived cyclone.<\/span><\/p>\n

The team found that whether a cyclone develops depends on two parameters: the size of the planet relative to the size of an average thunderstorm on it, and how much storm-induced energy is in its atmosphere. Given these two parameters, the researchers predicted that Neptune, which bears similar polar hotspots, should generate transient polar cyclones that come and go, while Jupiter should have none.<\/span><\/p>\n

Morgan O\u2019Neill, the paper\u2019s lead author and a former PhD student in MIT\u2019s Department of Earth, Atmospheric and Planetary Sciences (EAPS), says the team\u2019s model may eventually be used to gauge atmospheric conditions on planets outside the solar system. For instance, if scientists detect a cyclone-like hotspot on a far-off exoplanet, they may be able to estimate storm activity and general atmospheric conditions across the entire planet.<\/span><\/p>\n

\u201cBefore it was observed, we never considered the possibility of a cyclone on a pole,\u201d says O\u2019Neill, who is now a postdoc at the Weizmann Institute of Science in Israel.<\/span><\/p>\n

\u201cOnly recently did Cassini give us this huge wealth of observations that made it possible, and only recently have we had to think about why [polar cyclones] occur.\u201d<\/span><\/p>\n

O\u2019Neill\u2019s co-authors are Kerry Emanuel, the Cecil and Ida Green Professor of Earth, Atmospheric and Planetary Sciences, and Glenn Flierl, a professor of oceanography in EAPS.<\/span><\/p>\n

Beta-drifting toward a cyclone<\/strong><\/span><\/p>\n

Polar cyclones on Saturn are a puzzling phenomenon, since the planet, known as a gas giant, lacks an essential ingredient for brewing up such storms: water on its surface.<\/span><\/p>\n

\u201cThere\u2019s no surface at all \u2014 it just gets denser as you get deeper,\u201d O\u2019Neill says. \u201cIf you lack choppy waters or a frictional surface that allows wind to converge, which is how hurricanes form on Earth, how can you possibly get something that looks similar on a gas giant?\u201d<\/span><\/p>\n

The answer, she found, may be something called \u201cbeta drift\u201d \u2014 a phenomenon by which a planet\u2019s spin causes small thunderstorms to drift toward the poles. Beta drift drives the motion of hurricanes on Earth, without requiring the presence of water. When a storm forms, it spins in one direction at the surface, and the opposite direction toward the upper atmosphere, creating a \u201cdipole of vorticity.\u201d (In fact, videos of hurricanes taken from space actually depict the storm\u2019s spin as opposite to what\u2019s observed on the ground.)<\/span><\/p>\n

\u201cThe whole atmosphere is kind of being dragged by the planet as the planet rotates, so all this air has some ambient angular momentum,\u201d O\u2019Neill explains. \u201cIf you converge a bunch of that air at the base of a thunderstorm, you\u2019re going to get a small cyclone.\u201d<\/span><\/p>\n

The combination of a planet\u2019s rotation and a circulating storm generates secondary features called beta gyres that wrap around a storm and essentially split its dipole in half, tugging the top half toward the equator, and the bottom half toward the pole.<\/span><\/p>\n

The team developed a model of Saturn\u2019s atmosphere and ran hundreds of simulations for hundreds of days each, allowing small thunderstorms to pop up across the planet. The researchers observed that multiple thunderstorms experienced beta drift over time, and eventually accumulated enough atmospheric circulation to create a much larger cyclone at the poles.<\/span><\/p>\n

\u201cEach of these storms is beta-drifting a little bit before they sputter out and die,\u201d O\u2019Neill says. \u201cThis mechanism means that little thunderstorms \u2014 fast, abundant, but not very strong thunderstorms \u2014 over a long period of time can actually accumulate so much angular momentum right on the pole, that you get a permanent, wildly strong cyclone.\u201d<\/span><\/p>\n

Next stop: Jupiter<\/strong><\/span><\/p>\n

The team also explored conditions in which planets would not form polar cyclones, even though they may experience thunderstorms. The researchers found that whether a polar cyclone forms depends on two parameters: the energy within a planet\u2019s atmosphere, or the total intensity of its thunderstorms; and the average size of its thunderstorms, relative to the size of the planet itself. Specifically, the larger an average thunderstorm compared to a planet\u2019s size, the more likely a polar cyclone is to develop.<\/span><\/p>\n

O\u2019Neill applied this relationship to Saturn, Jupiter, and Neptune. In the case of Saturn, the planet\u2019s atmospheric conditions and storm activity are within the range that would generate a large polar cyclone. In contrast, Jupiter is unlikely to host any polar cyclones, as the ratio of any storm to its overall size would be extremely small. The dimensions of Neptune suggest that polar cyclones may exist there, albeit on a fleeting basis.<\/span><\/p>\n

The researchers are eager to see whether their predictions, particularly for Jupiter, bear out. Next summer, NASA\u2019s Juno spacecraft is scheduled to enter into an orbit around Jupiter, kicking off a one-year mission to map and explore Jupiter\u2019s atmosphere.<\/span><\/p>\n

\u201cIf what we know about Jupiter currently is correct, we predict that we won\u2019t see these wildly strong cyclones,\u201d O\u2019Neill says. \u201cWe\u2019ll find out next year if our predictions are true.\u201d<\/span><\/p>\n

This research was funded in part by the National Science Foundation.<\/span><\/p>\n","protected":false},"excerpt":{"rendered":"

New model may predict cyclone activity on other planets. CAMBRIDGE, Mass—\u00a0For the last decade, astronomers have observed curious \u201chotspots\u201d on Saturn\u2019s poles. In 2008, NASA\u2019s Cassini spacecraft beamed back close-up images of these hotspots, revealing them to be immense cyclones, each as wide as the Earth. Scientists estimate that Saturn\u2019s cyclones may whip up 300 […]<\/p>\n","protected":false},"author":6,"featured_media":4719,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[17,20],"tags":[],"class_list":["post-4718","post","type-post","status-publish","format-standard","has-post-thumbnail","hentry","category-research","category-space-news"],"featured_image_urls":{"full":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-Planet-Thunder-01.jpg",639,426,false],"thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-Planet-Thunder-01-150x150.jpg",150,150,true],"medium":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-Planet-Thunder-01-300x200.jpg",300,200,true],"medium_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-Planet-Thunder-01.jpg",639,426,false],"large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-Planet-Thunder-01.jpg",639,426,false],"1536x1536":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-Planet-Thunder-01.jpg",639,426,false],"2048x2048":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-Planet-Thunder-01.jpg",639,426,false],"ultp_layout_landscape_large":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-Planet-Thunder-01.jpg",639,426,false],"ultp_layout_landscape":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-Planet-Thunder-01.jpg",639,426,false],"ultp_layout_portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-Planet-Thunder-01.jpg",600,400,false],"ultp_layout_square":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-Planet-Thunder-01.jpg",600,400,false],"newspaper-x-single-post":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-Planet-Thunder-01.jpg",639,426,false],"newspaper-x-recent-post-big":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-Planet-Thunder-01.jpg",540,360,false],"newspaper-x-recent-post-list-image":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-Planet-Thunder-01.jpg",95,63,false],"web-stories-poster-portrait":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-Planet-Thunder-01.jpg",639,426,false],"web-stories-publisher-logo":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-Planet-Thunder-01.jpg",96,64,false],"web-stories-thumbnail":["https:\/\/www.revoscience.com\/en\/wp-content\/uploads\/2015\/06\/MIT-Planet-Thunder-01.jpg",150,100,false]},"author_info":{"info":["Amrita Tuladhar"]},"category_info":"Research<\/a> Space\/ AstroPhysics<\/a>","tag_info":"Space\/ AstroPhysics","comment_count":"0","_links":{"self":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/4718","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/users\/6"}],"replies":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/comments?post=4718"}],"version-history":[{"count":0,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/posts\/4718\/revisions"}],"wp:featuredmedia":[{"embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media\/4719"}],"wp:attachment":[{"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/media?parent=4718"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/categories?post=4718"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.revoscience.com\/en\/wp-json\/wp\/v2\/tags?post=4718"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}