Multi-year monitoring enables an understanding of the distribution of clouds in the different seasons
Many of Titan's clouds can be seen in infrared images. They form and move like those of Earth, albeit at a slower rate. In the observations that continued 3.5. Years from July 2004 to December 2007 more than 200 clouds were seen. The way they are distributed around Titan is consistent with what was assumed in various models (1). The difference between these clouds and the clouds of the earth is that their movement is not exactly parallel to the seasons. Titan may have been hotter and more humid in the early fall than expected. In 2004, towards the end of the summer in the Southern Hemisphere, extensive clouds were seen over the South Pole (2). Since 2005 the monitoring of the south polar clouds has been more limited. A year after the equinox (the time when the sun is above the equator of Saturn and its moons) which occurs once every 15 years, clouds were seen in a wide area near the equator (3).
In 2007, a large cloud was detected east of the Kraken Mare sea. When this lake is in Milou, its area reaches 400,000 square kilometers. Additional clouds were indeed observed, but according to the researchers' assessment, even if these clouds are not directly related to lakes and seas, it seems that the discovery of these clouds with high frequency at high latitudes in the Northern Hemisphere is related to the large explosion of methane on the ground in this region (4).
Photographs taken between May 2008 and December 2009 show the disappearance of clouds over the North Pole. In one of these photographs the clouds seen in S 0 40 even after the Equinox continued to be active. The first time clouds were seen in this area was during the summer in the southern hemisphere. The August 2009 equinox itself saw seasonal changes as Titan moved from summer in the southern hemisphere to spring in the northern hemisphere. In the 6 years of observation, the Cassini saw cloud clusters in 3 areas at different latitudes - large clouds in the North Pole, patches of clouds in the Southern Hemisphere and a narrow band in the S 0 40 latitude. The researchers noticed signs of seasonal changes on Titan. Clouds in the South Pole disappeared just before the equinox and clouds in the Northern Hemisphere became thinner. These changes were consistent with models that predicted seasonal changes from one hemisphere to the other during winter in the Northern Hemisphere. In Titan's troposphere, ethane clouds formed at the North Pole. The source of these clouds is a flow of ethane and aerosols from a very high altitude - the stratosphere. in the southern hemisphere. The atmospheric gases are enriched with methane that rose from the ground and formed clouds in middle and high latitudes (5).
For two and a half years, you will observe Titan using terrestrial telescopes. These observations were made from mid-spring until near the end of this season in the Northern Hemisphere. During this period few clouds were seen in the atmosphere. On 13.4.2008 there was a dramatic increase in cloud activity. On observation nights made after this date, a cloud system began to develop at latitude S 0 30. After a few days, additional clouds began to appear over the tropical regions and over the South Pole. At this time of the year there should not have been any clouds at this pole. The conclusion was that clouds can form anywhere. without any correlation to the models they thought of. On Titan a storm in one place can cause clouds and storms to form in another. The course of the formation of channels and the depressions at the bottom (streambed) in the tropical desert of Titan can be explained by heavy rains in short periods of time but with an extremely strong intensity, as in the terrain route in the southwest of the USA (6).
The phenomenon of the formation of clouds in one place, which can cause the formation of clouds in one place, is known in the country and its name is atmospheric teleconnections (atmospheric) and it is created by Rossby waves (7). These waves are created when air from the pole moves towards the equator and at the same time Tropical air moves towards the pole Due to the temperature differences between the equator and the poles caused by the solar radiation reaching them, the air moves from low latitudes to high latitudes.
At the beginning of 2011 it was reported about the presence of thin clouds (wispy clouds) made of ice particles and similar to cirrus clouds on Earth. Unlike Titan's brown haze, the thin clouds look like white pearls of fresh snow. These clouds are at a higher altitude than the clouds observed earlier. They are also thinner. The creation of the clouds as a whole is done at high altitude, places where part of the methane breaks down and forms ethane and other hydrocarbons or they combine with nitrogen and form substances called nitriles. This large amount of materials accumulates to the amount suitable for the formation of clouds.
The low temperature essential for cloud formation is created deep within the atmosphere. It is believed that the various compounds are moved downward by a steady stream of gas coming from the pole. of the warm hemisphere towards the opposite pole, where it is colder and sinks. These circulation patterns take a large enough amount of gas from the warm hemisphere to measure the instability of the atmosphere. This flux of gas transports more clouds to the colder hemisphere. The colder the air, the greater amount of gas condenses. At this height of the clouds, an additional amount of gas flows. In the southern hemisphere, measurements were made at 3 locations at latitude S 0 58 and on both sides of the equator at N 0 15 and S 0 15, which makes it possible to identify clouds in these places. The measurements confirmed the hypothesis that in the Northern Hemisphere the amount of clouds was 3 times greater than in the Southern Hemisphere (8).
The big storms, including the arrow-shaped storm, can increase the amount of rain very significantly. The amount of rainfall can be 20 times the seasonal precipitation average (9). Titan's large albedo prevents much of the sun's radiation from reaching the ground. As a result, the atmosphere is more stable because it is heated more from above than from the ground. The solar energy that does reach the ground in the polar region evaporates methane from the lakes and drives convection currents that form clouds (10). The researchers noticed that clouds observed in the last decade during the summer in the southern hemisphere cluster in middle and high latitudes (11).
Sources
1. PIA12004: Titan's lingering clouds
http://photojpornal.jpl.nasa.gov/catalog/PIA12004
2. "Saturn's Titan : A unique world in the solar system- Could life there be Methane based" 18.5.2011
http://www.dailygalaxy.com/my-weblog/20110/05/saturns-Titan-a-unique-world-in -the-solar-system-could-life- there -be- methane –based.html?source=feedu
3. PIA12813: Titan's moving mid-latitude clouds
http://photojpornal.jpl.nasa.gov/catalog/PIA12813
4. PIA12811: Titan's northern polar cloud
http://photojpornal.jpl.nasa.gov/catalog/PIA12811
5. PIA13400: Clouds Clearing around Titan's north pole
http://photojpornal.jpl.nasa.gov/catalog/PIA13400
6. "Clouds discovered over tropics of Saturn's moon" 12.8.2009
http://www.spaceflightnow.com/news/0908/12titan
7. "Storm brews over Titan's tropical desert" 20.8.2009
http://www.saturndaily.com/reports/Storm_Breas_Over_Titan_ Tropical_ Desert_999.html
8. Zubitisky E. - "Surprises hidden in Titan's smog cirrus -like clouds" 4.2.2011
http://www.spacedaily.com/reports/Surprises_Hidden_In_Titan’s_Smog_Cirrus_Like_ Clouds_999.html
9. "What caused a giant arrow-shaped cloud on Saturn's moon Titan" 18.8.2011
http://www.spacedaily.com/reports/What_Caused_A_Giant_Arrow_Shaped_Cloud_ On _Saturns _Moon _Titan_999.html
10. Johnson Scott K.- "Figuring out why most of Titans' s Methane lakes have northern exposure" 1/2012
http://arstechnica.com/science/news/2012/01/titans-methane-lake-have-northern-bias.ars
11. "Three enduring mysteries of Saturn's Titan solved" 4.1.2012
http://www.dailygalaxy.com/my-weblog/2012/01/ Three lingering mysteries of Saturn’s Titan solved.html
