Cloud Properties and Its Relation to Precipitation over Northwest China

The temporal and spatial distribution of cloud properties over Northwest China has been analyzed using the ISCCP (International Satellite Cloud Climatology Project) monthly mean D2 data from July 1983 to September 2001. The result shows that the regional average total cloud amount, optical thickness, and water path are 52.5%-58.3%, 2.6-6.6, and 44.9-77.6 g m-2, respectively. The major feature of spatial distribution is that higher value areas of cloud properties are all over Tianshan, Kunlun, and Qilian Mountains, while the lower values of cloud properties are over Tarim Basin, the western desert of Inner Mongolia, and the northwestern part of the Loess Plateau. The higher values of cloud amounts are generally associated with higher level of precipitation. For example, the amounts of stratiform clouds with large water path values are good consistent with precipitation. But the amounts of cumuliform and stratocumuliform clouds do not have de nite relation to precipitation.