Group seminar on 31. January, 14:15 CET
The role of subtropical highs regarding to the low cloud formation
Previous studies has highlighen the importance of low stratiform clouds, which cover more of Earth’s surface than any other cloud types and play crucial roles in the global engergy budget. They are found to prefer the downstream position of subtropical highs. Subtropical highs could provide strong lower-tropospheric stability, large-scale subsidence, and a ready supply of surface moisture. And they create conditions for inversions beyond the low clouds. This study take the hypothesis that the lower-tropospheric stability and humidity can influence the fraction of low clouds. The lower-tropospheric stability can be regarded as a measure of the strength of the inversion, while a stronger inversion is more effective at trapping moisture within the marine boundary layer. The larger lower-tropospheric stability permits more cloud cover. Based on the linear-positive correlation between low cloud cover and these factors, this research further explores the variation of subtropical highs with respect to the conditions of low cloud formation. The difference among five major subtropical highs and their seasonal cycles is compared, and the reasons of that variation from heat and moisture transport perspective are analyzed.