(ORDO NEWS) — Clouds in the Southern Hemisphere are lighter than in the Northern Hemisphere due to the increased moisture content associated with the small land area and internal gravity waves in the atmosphere.
It would seem that the air does not care in which hemisphere of the planet it is located: the clouds should be the same – both in the North and in the South. However, as observations show, in the Southern Hemisphere of the Earth, the clouds are thicker and lighter; they reflect more incident solar radiation than clouds at the same latitudes in the Northern Hemisphere.
Southern clouds occur less frequently and contain fewer ice particles, but more moisture. This difference was noticed decades ago, but until recently had no good explanation. It was also investigated by the authors of a new article published in the journal Atmospheric Chemistry and Physics .
Martin Radenz and colleagues at the Leibniz Institute for Tropospheric Research (TROPOS) used three-year cloud monitoring data for Leipzig (Germany) and Limassol (Cyprus) in the Northern Hemisphere, as well as for the Chilean Punta Arenas in the Southern Hemisphere.
Observations using radars and lidars were carried out in 2018-2021, within the framework of the DACAPO-PESO project. They showed that at the height of the troposphere, with temperatures between minus 24 and minus eight degrees, 10-40 percent less cloudiness forms over Punta Arenas than over cities in the Northern Hemisphere.
It is worth recalling that the ocean covers a much larger part of the Earth’s southern hemisphere. As a result, fewer fine dust particles enter the air from land. Once at a suitable height, these particles serve as condensation centers – “embryos” on which water droplets form and freeze, forming clouds.
As a result, Southern Hemisphere clouds, other things being equal, contain fewer ice particles and more moisture. “And this means that they interact with the incident sunlight and thermal radiation rising from the Earth differently than in the north,” says Patric Seifert, one of the authors of the work.
Such conclusions have been made before , but a new study has found another interesting mechanism associated with internal gravity waves (IGWs) – air vibrations that occur when it flows around a mountain landscape. Powerful westerly winds coming from the Pacific Ocean rest against the peaks of the Andes and rush to great heights.
Due to this, even at temperatures below minus 25 degrees, the air is saturated with moisture, which is completely uncharacteristic for other regions of the planet. Thus, the differences in the cloudiness of the Northern and Southern Hemispheres can be explained by the different number of aerosol particles in the air, as well as by ascending IGW fluxes.
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