page_title: Atmosphere of Jupiter
section_title: Circumpolar cyclones
hierarchical_section_title: Atmosphere of Jupiter / Discrete features / Circumpolar cyclones
caption_attribution_description: English: This image shows the southern circumpolar cyclones on Jupiter that was taken by JIRAM.
context_page_description: The atmosphere of Jupiter is the largest planetary atmosphere in the Solar System. It is mostly made of molecular hydrogen and helium in roughly solar proportions; other chemical compounds are present only in small amounts and include methane, ammonia, hydrogen sulfide and water. Although water is thought to reside deep in the atmosphere, its directly measured concentration is very low. The nitrogen, sulfur, and noble gas abundances in Jupiter's atmosphere exceed solar values by a factor of about three.
  The atmosphere of Jupiter lacks a clear lower boundary and gradually transitions into the liquid interior of the planet. From lowest to highest, the atmospheric layers are the troposphere, stratosphere, thermosphere and exosphere. Each layer has characteristic temperature gradients. The lowest layer, the troposphere, has a complicated system of clouds and hazes, comprising layers of ammonia, ammonium hydrosulfide and water. The upper ammonia clouds visible at Jupiter's surface are organized in a dozen zonal bands parallel to the equator and are bounded by powerful zonal atmospheric flows known as jets.
context_section_description: Other notable features of Jupiter are its cyclones near the northern and southern poles of the planet. These are called circumpolar cyclones (CPCs) and they have been observed by the Juno Spacecraft using JunoCam and JIRAM. The cyclones have only been observed for a relatively short time from perjoves 1-15 which is approximately 795 days or two years. The northern pole has eight cyclones moving around a central cyclone (NPC) while the southern pole only has five cyclones around a central cyclone (SPC), with a gap between the first and second cyclones. The cyclones look like the hurricanes on Earth with trailing spiral arms and a denser center, although there are differences between the centers depending on the individual cyclone. Northern CPCs generally maintain their shape and position compared to the southern CPCs and this could be due to the faster wind speeds that are experienced in the south, where the average wind speed around 80 m/s to 90 m/s. Although there is more movement among the southern CPCs they tend to retain the pentagonal structure relative to the pole. It has also been observed that the angular wind velocity increases as the center is approached and radius becomes smaller, except for one cyclone in the north, which may have rotation in the opposite direction. The difference in the number of cyclones in the north compared to the south is due to the size of the cyclones. The southern CPCs tend to be bigger with radii ranging from 5,600 km to 7,000 km while northern CPCs range from 4,000 km to 4,600 km.
  The northern cyclones tend to maintain an octagonal structure with the NPC as a center point. Northern cyclones have less data than southern cyclones because of limited illumination in the north-polar winter, making it difficult for JunoCam to obtain accurate measurements of northern CPC positions at each perijove (53 days), but JIRAM is able to collect enough data to understand the northern CPCs. The limited illumination makes it difficult to see the northern central cyclone, but by making four orbits, the NPC can be partially seen and the octagonal structure of the cyclones can be identified. Limited illumination also makes it difficult to view the motion of the cyclones, but early observations show that the NPC is offset from the pole by about 0.5˚ and the CPCs generally maintained their position around the center. Despite data being harder to obtain, it has been observed that the northern CPCs have a drift rate of about 1˚ to 2.5˚ per perijove to the west. The seventh cyclone in the north (n7) drifts a little more than the others and this is due to an anticyclonic white oval (AWO) that pulls it farther from the NPC, which causes the octagonal shape to be slightly distorted.
  Current data shows that the SPC shows a positional variation between 1˚ and 2.5˚ in the latitude and stays between 200˚ to 250˚ longitude and has shown evidence of this recurring approximately every 320 days. The southern cyclones tend to behave similarly to the northern ones and maintain the pentagonal structure around the SPC, but there is some individual movement from some of the CPCs. The southern cyclones don't move around the south pole, but their rotation is more steady around the SPC, which is offset from the pole. Short term observation shows that the southern cyclones move approximately 1.5˚ per perijove, which is small compared to the wind speeds of the cyclones and the turbulent atmosphere of Jupiter. The gap between cyclones one and two provides more movement for those specific CPCs, which also causes the other cyclones that are close to move as well, but cyclone four moves less because it is farthest from the gap. The southern cyclones move clockwise individually, but their movement as a pentagonal structure moves counter-clockwise and drifts more toward the west. 
  
  The circumpolar cyclones have different morphologies, especially in the north, where cyclones have a "filled" or "chaotic" structure. The inner part of the “chaotic” cyclones have small-scale cloud streaks and flecks. The “filled” cyclones have a sharply-bo
caption: JIRAM image of southern CPCs
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