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The pattern of circulation in Earth\u2019s atmosphere is pretty straightforward. The Sun warms air around the equator that rises, then rolls over through high altitudes before sinking down to the ground at latitudes near 30\u00b0 north and south (around a third of the way to the poles). From there the moving air blows across Earth\u2019s surface back to the equator. This is a giant convection current \u2013 just like the one that churns over the radiator in your living room \u2013 and the pair straddling Earth\u2019s equator are called the Hadley cells.<\/p>\n\n
There are three great atmospheric circulation cells in each of Earth\u2019s hemispheres. The middle cell of each trio (called the Ferrel cell) is driven round by its neighbours like a cog. Since all of this results in a flow of the atmosphere across latitudes between the equator and pole, the system is known as meridional circulation and it creates the prevailing winds, such as the trade winds and westerlies.<\/p>\n\n
The stripey appearance of Jupiter is also believed to be due to meridional circulation in the atmosphere, but this is much more obvious than on Earth because the rising and sinking regions of Jupiter\u2019s atmosphere cause conspicuous differences in the cloud layers and colours. The horizontal pale \u2018zones\u2019 are caused by upwelling and the formation of high-altitude ammonia ice, and the \u2018belts\u2019 are ruddy-coloured clouds where the air is descending. There are also powerful jet streams in between.<\/span><\/p>\n\n What we don\u2019t know, however, is what happens to these circulation cells deep in Jupiter\u2019s interior \u2013 there\u2019s no solid lower boundary like there is with Earth\u2019s surface. Keren Duer, at the Weizmann Institute of Science in Israel, and her team have been using data returned by the Juno mission to try and find out. Since 2016, when it arrived at Jupiter, NASA\u2019s probe has been measuring the light being reflected off the gas giant at different wavelengths, including infrared and microwave. Any light that\u2019s able to penetrate the top cloud layer allows us, to some degree, to peer into the planet\u2019s interior.<\/p>\n\n By looking at the microwave data from Juno, the team was able to track the ammonia in Jupiter\u2019s atmosphere. This revealed the presence of a series of regions of upwelling and downwelling hidden beneath the visible upper clouds in the midlatitudes of Jupiter \u2013 between 60\u00b0 south and 60\u00b0 north. These form eight deep circulation cells in each hemisphere of the planet, like a whole set of rollers side-byside. And, in a similar way to the middle Ferrel cell in each of Earth\u2019s hemispheres, Jupiter\u2019s mid-latitude circulation cells are driven by active convection at the equator. However, while Earth only has one Ferrel cell in each hemisphere, Jupiter has eight due to its larger size and faster spin.<\/span><\/p>\n\n Duer\u2019s team was able to trace these deep meridional circulation cells by observing ammonia in the microwave data. This only allows detection down to a few hundred kilometres below the cloud decks, so we know Jupiter\u2019s Ferrel cells extend at least as far as that. It\u2019s not the whole story, but it goes a long way towards understanding the atmospheric dynamics hidden beneath Jupiter\u2019s clouds.<\/p>\n\nBeneath the clouds<\/strong><\/h5>\n\n
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