Characteristics and Formation Mechanism of the Cloud Vertical Structure Over the Southeastern Tibetan Plateau in Summer

Abstract

Abstract Cloud vertical structure (CVS) has important influence on cloud radiative effect and atmospheric circulation, especially for the third pole of the world–the Tibetan Plateau (TP). However, the characteristics and formation mechanism of the CVS over the TP are not well understood. This study revealed the characteristics and formation mechanism of the CVS over the southeastern Tibetan Plateau (SETP) in summer using the radiosonde datasets and the ERA5 data sets during June–August from 2015 to 2021. Results show that SETP is cloudy for 71% of the summertime with 73% of the clouds single–layered and 27% multi–layered. Multi–layer cloud occurs more frequently over the eastern SETP. With the number of cloud layers increases, the vertical range of cloud increases but the layer thickness and the inter–layer distance decrease. Water vapor, ascent, circulation and vertical wind shear are important factors for CVS formation. Single–layer cloud tends to form when the strengthening of the water vapor and the ascent is most significant at 400 hPa. In comparison, a stronger South Asian High (SAH) brings more water vapor and stronger ascent to the upper level, helping form the upper cloud and favoring the two–layer cloud structure. Three–layer cloud is likely to form when the upper–level vertical wind shear strengthens and the ascent between the middle and low cloud layer weakens. This study deepens the scientific understanding of the characteristics and formation mechanism of the CVS over the TP, and provides scientific reference for modeling the cloud–climate feedback process over the plateau.