Spatial-Temporal distribution of cloud covers over China during 2001-2020

Abstract

Information of cloud covers is the essential parameter to help better understand weather, climate, water cycle, and solar energy variation of the land surface, as well as the organization of effective satellite-based observations for numerous surface monitoring applications. Compared with traditional cloud information collected by limited ground stations, satellite remote sensing provides the opportunity to investigate the spatiotemporal features of cloud covers from above with actual measurements over global or regional scale. Few previous studies have explored the various cloud types globally or across China. In this work, the 20-year spatial and temporal distribution features and trends of various cloud types (clouds, cloud shadows and cirrus clouds) in China from 2001 to 2020 were investigated using MODIS daily surface reflectance product. Our results showed that: In terms of overall spatial distribution, the southeast was cloudy year-round with up to 75% cloud cover, while the northwest arid zone was mostly clear skies. Cloud shadows were mainly concentrated on complex undulating surfaces composed of high mountains, and cirrus clouds were mostly distributed in the northern regions of high latitudes. In recent 20 years, clouds showed a downward trend in North China, with an annual decreasing rate of more than 0.5% in Inner Mongolia, and a significant increasing trend of up to 0.6% in the middle and lower reaches of the Yangtze River. Cloud shadows had little change in trend in most parts of China. Cirrus clouds had a decreasing trend in most areas, especially in the Greater Khingan Mountains, where the decrease can reach 0.6%.