Spatial and Temporal Distributions of Warm Cloud Properties in Eastern China and Its Adjacent Ocean and Their Relationships with Meteorological Conditions

Spatial distribution and seasonal variation of cloud properties in eastern China and its adjacent ocean are analyzed based on MODerate resolution Imaging Spectroradiometer (MODIS) level three daily cloud products from 2003 to 2016. The relationships of cloud properties with dynamic and thermodynamic conditions and water vapor condition are investigated by combining MODIS and ERA-Interim reanalysis data over the same period. The high cloud fraction (CF) area is found over eastern China in the summer and over southern China and eastern ocean in the winter. The cloud droplet effective radius (CER) decreases from eastern ocean to inland region in both the summer and winter. Compared to that in the summer, the spatial distribution pattern of liquid water path (LWP) in the winter is greatly inhomogeneous with a dividing line between high and low values located near 30°N, which corresponds to the distribution of water vapor. It is found that CF exhibits the same seasonal variation over the land and ocean, i.e., low in summer and high in winter, but the magnitude is larger in eastern China land area than in the adjacent ocean. On the contrary, the CER and LWP are greater over the land than over its adjacent ocean with lower values in the winter and higher values in the summer. In general, CF has an obvious positive correlation with precipitable water vapor (PWV) and low troposphere stability (LTS) and a negative correlation with 850-hPa vertical velocity (ω_850hPa), which indicates that abundant moisture and ascending motion in lower levels are favorable for the formation of clouds while the stable atmospheric stratification suppresses the growth of clouds. This explains why cloud fraction in the middle and lower levels is high. Both the CER and LWP show negative correlations with LTS and ω_850hPa. However, they display low sensitivity to variations of PWV, which suggests that the CER and LWP are mainly affected by dynamic and thermodynamic lifting instead of the atmospheric moisture condition.