Liquid cloud drop effective radius over China: A 20-year MODIS-based assessment

Clouds are one of the most significant and uncertain components in weather forecasting and climate prediction. The 20-year detailed liquid water cloud effective radius (CER) over China from 2001 to 2020 are systematically studied based on the Moderate Resolution Imaging Spectroradiometer cloud products. The spatial distributions of CER show slight alterations of seasonal patterns of changes over China during 2001–2020. The monthly mean CER values over China vary from 12.7 μm in November to nearly 14.4 μm in July. The summer season has the largest average CER, followed by spring and winter, while autumn exhibits relatively lower CER levels over China. The mean CER values during 2001–2020 are found to be 14.7, 11.8 and 13.0 μm over the Tibetan Plateau, inland and coastal regions of China, respectively. High CERs in spring and winter are seen in the Tibet Plateau, whereas the reverse is true over the inland and coastal regions. The impacts of precipitable water vapor (PWV) and aerosol optical depth on the CER over China are complex, whereas the correlations between CER and PWV can be generally expressed by a two-stage linear fitting, showing distinct turning points in different seasons and regions. The CER over different regions of China shows an increase with enhanced PWV under low or high water vapor conditions as opposed to an increase of CER under moderate water vapor levels. Our study indicates a high CER in the Tibet Plateau and low over the Sichuan Basin, and significantly distinct impact of PWV on the CER in the Tibet Plateau.