What Causes the Low-Level Cloud Increase from April to May Over the Arctic Ocean?

Overall, clouds play a massive role in regulating the climate in the Arctic. The influence that Arctic clouds have on the temperature of the lower atmosphere varies based on the cloud type, latitude, and season. As a result, it is important to understand how Arctic cloud cover changes throughout the year, since they can influence sea ice loss and enhance Arctic warming. This project specifically focuses on examining the spatial and vertical extent of an observed low level cloud increase in May. Since May marks the beginning of the melt season, understanding this increase is quite important, especially considering the warming effect of Arctic clouds during this period. To conduct this Arctic cloud research, I used the 3S-GEOPROF-COMB data product created by Bertrand et al. (2023), which contains Arctic cloud data from 2006 to 2019. This globally gridded data product contains cloud vertical structure data from the CloudSat radar and CALIPSO lidar. Arctic sea ice data is from the National Snow and Ice Data Center, while potential temperature data is from the NOAA Physical Science Laboratory. Through my research, I determined that the May cloud increase has occurred exclusively in the lower levels of the troposphere (below 3.2 km). In addition, this low-level cloud increase is largest over the Arctic Ocean, and particularly the Beaufort Sea. Even though the greatest May cloud surge occurs over the ocean, this phenomenon does not coincide with a major sea ice decrease over the Arctic Ocean. However, a substantial decrease in low-level stability from April to May occurs in many of the same regions where the most significant low cloud increase takes place. Work leading up to the AMS conference will involve attempting to solve this May cloud mystery and determining whether the increase stems from a surface moisture uptick due to snow melt and ice leads, or if it pertains to atmospheric stability changes alone.

Figure: The map on the left shows the difference in low cloud cover from April to May. The central image shows the May minus April difference in sea ice concentration. The final graphic portrays the May minus April difference in low-level stability, which is represented by the potential temperature difference between 700 hPa and 1000 hPa. The black box outlines the area with the most significant low-level cloud increase. This data was evaluated from 2006 to 2019.