Satellite-derived cloud properties over China

Low-level water cloud (cloud top temperature more than 273K) properties such as the optical depth, particle radius, and verticallyintegrated droplet number concentration are derived from satellite remote sensing technique with Advanced High Resolution Radiometer (AVHRR) over the East Asia, mainly China area. Their annual mean characteristics thus obtained are consistent with what the Twomey effect indicates, showing larger optical depth and droplet number concentration, and smaller particle radius over land generally compared to those over ocean. Long-term analysis of cloud particle radius from 1985 to 1994 reveals gradual decrease with time for clouds over both land and ocean. This trend, however, would be affected by some crucial reasons. We need to be careful when we use long-term satellite data. Also, we estimate cloud spherical albedo and shortwave radiative flux by a fast parameterization method. Development of fast computation of cloud-relevant quantities will contribute to better understanding of climate problems.