Some studies found that the Southern Hemisphere has more clouds, and the Northern Hemisphere has more lands. Thus, the albedos of the two hemispheres almost equal to each other. This results in other phenomena, e.g., heat is transported from the Northern Hemisphere to the Southern Hemisphere in the atmosphere, the ITCZ is not at the equator but at the north side of the equator.
I wonder what determines that the Southern Hemisphere has more clouds than its counterpart naturally?
Please also have a look at these useful RG links.
Article The relationship between clouds and dynamics in Southern Hem...
Article Observational Analysis of Cloud and Precipitation in Midlati...
https://www.researchgate.net/post/Why_is_the_Southern_Ocean_so_cloudy
Even if this is not easy to answer to this question, some studies have found that the Southern oceans are no cloudier than the North Atlantic or Pacific oceans. The question may be posed as asking why the midlatitude storm track areas are so cloudy. Consider that there is a permanent polar vortex in the Antarctic delivering cold air northwards cross the Southern Ocean. This cold air undercuts the warm air forming in the Pacific, Atlantic and Indian Oceans in the Southern Hemisphere. So there is a region where these two air masses meet and permanent cloud results from the induced cyclonic systems.
In the Northern Hemisphere however the polar vortex breaks down in the summer when the Arctic sea melts and leads in the ice are found. The surface of this hemisphere is dominated by the Euro-asian and North American continents which restrict the flow of water vapour into the atmosphere. Therefore, the cloud band seen in the Southern Hemisphere may have a larger extent.
In DJF the SH jet stream region always has large cloud fraction, and most of them are low clouds, I was wondering why. On the other hand SH is much clean in aerosol which is not beneficial to clouds. My feeling is that sulfates are better for CCN than sea salts.
Dear all, thank you for the valuable answers. Raffaele Salerno, I only read studies on hemispheric scales, but I think you are right, the important cloudy area is in the SH mid-latitude, which equalizes the hemispheric albedo.
According to the study recently reported by NASA researchers, the main reason for the cloud field asymmetry over the tropical Atlantic Ocean (30° N–30° S) is the presence of Saharan dust. The summary of the results is shown in Figure 5 of the Kishcha et al. (2015): "Saharan dust as a causal factor of hemispheric asymmetry in aerosols and clouds over the tropical Atlantic Ocean", the text available on the following web page:
https://www.tandfonline.com/doi/pdf/10.1080/01431161.2015.1060646?needAccess=true
To estimate the extent of the phenomenon of the Sahara Aerosol Layer (SAL), please consult the following satellite image from NASA.
Dear all,
Thanks for your valuable answers, from which a conclusion can be drawn that the surface condition (more ocean in the Southern Hemisphere) maybe the reason for the cloudiness of the Southern Hemisphere. Please allow me to further this question. What is the nature of the ITCZ at the north side of the equator? What kind of role do the Southern Hemispheric clouds play in the phenomenon, and how they play?
Thank you for sharing the paper Kenneth M Towe
. It is very useful for me.
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