Diurnal variations of cloud optical properties during day-time over China based on Himawari-8 satellite retrievals

Abstract

Cloud effective radius (CER) and cloud optical thickness (COT) are two important variables to characterize the optical properties of clouds which facilitate the understanding of cloud radiation. In this study, Japanese Himawari-8 (H8) geostationary satellite cloud retrieval data are used to depict the spatial and temporal variations of CER and COT during day-time in various seasons over China from September 2015 to August 2020. Our results show that northern China tends to have relatively larger CER and smaller COT than southern China. Overall, the CER increases while the COT decreases during the day-time period. In particular, the CER diurnal variation in northern China is stronger than that in southern China in winter. However, the southern China generally has stronger COT diurnal variation than the northern China. For the local sub-regions, the largest diurnal variations of CER and COT occur over the Tibetan Plateau (TP). Specifically, the Southeastern TP usually has larger COT and smaller CER compared with the Western TP. This study implies the importance of considering diurnal variations of cloud properties in the evaluation of the radiative effects of clouds.