Observational characteristics of summer non-precipitating clouds in Jiulong on the east side of the Qinghai-Tibet Plateau

Abstract

Jiulong is located on the east side of the Qinghai-Tibet Plateau (QTP) and is a region prone to southwest vortex. Cloud detection with new-type detection equipment in this region helps enhance the knowledge of cloud characteristics in the southwest vortex-prone region. In this study, based on the ground-based microwave radiometer data from June to August of 2018-2019 in Jiulong, the observational characteristics of cloud occurrence frequency (COF), liquid water path (LWP), and supercooled liquid water path (SLWP) for non-precipitating clouds during the summer seasons are investigated. The results are as follows. The monthly average COF of summer non-precipitating clouds in Jiulong is between 67%-82%, with low and middle clouds being the main types, and high clouds being less common. For low clouds, the COF is low in daytime and high in nighttime, while it is the opposite for middle and high clouds. The vertical distribution of COF presents an unimodal pattern, with a peak of 8.1% at a height of about 2 km. Due to the diurnal variation of atmospheric thermal stratification, the unimodal pattern of COF shows diurnal differences. Moreover, the average LWP of summer non-precipitating clouds in Jiulong is 0.433 kg·m-2, with the average LWPs of low, middle, and high clouds being 0.665, 0.240, and 0.102 kg·m-2, respectively. The diurnal variation of LWP in low clouds is similar to their COF, while the diurnal variations of LWP in middle and high clouds are not significant. Additionally, the average SLWP of cold clouds among summer non-precipitating clouds in Jiulong is 0.154 kg·m-2, with the average SLWPs of low, middle, and high clouds being 0.065, 0.166, and 0.102 kg·m-2, respectively. On the whole, the proportion of SLWP in LWP is about 34.3%-38.8%. The proportion of SLWP increases with the height of the cloud, which makes the diurnal variations of SLWP in middle and high clouds similar to that of LWP. Compared with central China, the characteristics of summer non-precipitating clouds in Jiulong are significantly different, and this is closely related to the different characteristics of atmospheric water vapor between the two regions.

Keywords

• qinghai-tibet plateau
• southwest vortex
• non-precipitating cloud
• cloud occurrence frequency
• liquid water path
• supercooled liquid water path