The Rapid Cloud Compensation Phenomenon Could Provide Another Piece of Climate Puzzle

Researchers at North Carolina State University described the rapid and dramatic clearing of low cloud cover off the southwestern coast of Africa. This newly observed phenomenon could help climatologists understand how clouds affect the warming and cooling of the Earth.

Sandra Yuter, North Carolina State Atmospheric Scientist and his wife, reviewed many years of satellite data from NASA and the European Organization for Climate Change. ### Exploitation of Meteorological Satellites. The team noticed steep clearings of cloud cover off the coasts of Namibia and Angola.

"Large areas of low cloud are a normal feature over the ocean in subtropical regions in the western continents," Yuter said. "What is unusual in this case is that erosion of clouds occurs rapidly along an organized line several hundred kilometers long, like a cloud of sun torn off." The lines can move west for a day or more and clear a cloud area more than twice that of California. "

The rapid events of cloud removal occur throughout the year and peak in May – occurring on more than half of the days of the month." Yuter and his team noted that the direction of the wind at the cloud level was often perpendicular to that of the clearing.This shows that the cloud is not repelled by the wind.The clearings leave the coast around midnight and continue any the night and the next day, suggesting that solar heating does not cause these events. "This type of cloud erosion has never been documented before," says Yuter. "The way this is done Pass is still a mystery, although we theorize that atmospheric gravity waves are the most likely mechanism. "These waves cause movements up and down in the atmosphere, similar to a boat that floats on the air. We hypothesize that the Africa's offshore winds interact with stable air over the ocean to make these waves, which cross the cloud field and promote the mixing and evaporation of clouds.

Yuter believes that this discovery will improve the understanding of climate processes "We were very surprised by what we found," she says, "it's a way to change large cloudy areas that n & # 39; It has not been documented before Scientists are interested in anything that changes the low cloud area over the ocean because these clouds reflect sunlight and cool the ocean. Earth. "Understanding how this happens will help us predict what might happen to clouds in a warm climate. . "It's about balancing the effects of warming and cooling – and it's one of the pieces that make up that balance."

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The research appears in Science and was supported by the National Science Foundation (grants AGS 1656237 and 1656314) and the US Department of Energy (grants DE- SC0006701, DE-SC0006736 and DE-SC0016522). Yuter, emeritus professor of marine science, earth and atmosphere, is the first and corresponding author of the work. Matthew Miller, Principal Investigator in the State of North Carolina, John Hader, former NC State graduate student, and David Mechem, Associate Professor in the Department of Geography and Atmospheric Sciences of the University of Kansas, contributed to the work.

Note to Editors: A summary of the article follows.

"Sudden clearing of marine stratocumulus in the subtropical southeastern Atlantic"

DOI: 10.1126 / science.aar5836

Authors: Sandra Yuter, John Hader, Matthew Miller, State University of North Carolina; David Mechem, University of Kansas

Published: Science

Abstract:

We document rapid and dramatic clearings of large portions of the low-altitude subtropical marine cloud deck that have implications for global radiative balance and climate sensitivity. In the southeastern Atlantic, large areas of stratocumulus erode rapidly and produce partial or complete clearing along sharp transitions of 100 to 1000s of km moving westward to 8 km. -12m ​​s-1 and move up to 1000+ km from the African coast. The cloud cover moving west has an annual peak in April-May-June. Cloud erosion limits reduce clouds to a 10 km scale in less than 15 minutes, move approximately perpendicular to the average flow, and often accompany cloud patterns. 39, small-scale waves. Observations suggest that cloud erosion is caused by atmospheric gravity waves.

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