Vertical structure of stratocumulus clouds and associated dynamics over the Arabian Sea during Indian summer monsoon season

Abstract

Five years of CloudSat observations during the Indian summer monsoon (ISM) season are used to investigate the vertical structure of stratocumulus (Sc) clouds and associated dynamics over the western part of Arabian Sea. The amount of Sc clouds formed over these regions are quantified in terms of their frequency of occurrence (FOC) and the same is used to study their vertical structure, which is very important from their radiative impact standpoint. The analysis revealed that Sc clouds predominantly form in the 0.5- to 3-km altitude region with mean thickness of 2.5 km over the study region. However, the maximum FOC of Sc clouds is found at ∼1.2-km altitude. The prevailing meteorological conditions over the study region are also investigated using ERA-Interim reanalysis datasets, to figure out why the Sc clouds persistently form over this region during ISM period. The analysis revealed that the presence of strong thermal inversion at 850-hPa level formed due to large-scale subsidence, presence of a low-level jet at 850-hPa level, and the advection of dry air at 650-hPa level from the Arabian Desert lead to the inhibition of vertical development of Sc clouds over the Arabian Sea. The significance of the present study lies in characterizing the vertical structure of Sc clouds formed persistently over the Arabian Sea during ISM and divulging the prevailing dynamics and thermal structure responsible for the formation of the Sc clouds over the study region.