Cloudiness characteristics over Southeast Asia from satellite FY-2C and their comparison to three other cloud data sets

摘要

Fengyun-2C (FY-2C), launched in October 2004, is the first operational geostationary meteorological satellite in China. It can provide 1-h interval cloudiness products with a spatial resolution of 0.04 latitude 0.04 longitude. The main characteristics of the regional-scale clouds from a 2-year FY-2C data set (from July 2005 to June 2007) are presented, including the spatial distribution and the annual and diurnal cycles of cloudiness. The reliability of FY-2C cloud products over Southeast Asia is investigated through comparisons to cloud cover from the International Satellite Cloud Climatology Project, the Moderate Resolution Imaging Spectroradiometer on board Terra and Aqua satellites, and conventional ground observations. It is shown that the FY-2C cloud mask performs consistently with other cloud mask products over Southeast Asia. In the boreal winter, the whole domain is dry with little cloudiness. More extensive cloudiness can be observed over the Sichuan Basin, in the East China Sea and the South China Sea, along the northwestern border of China, and around the ITCZ in the Southern Hemisphere. In the boreal summer, the summer monsoon is the dominant system for the studied domain, which is generally humid with extensive cloudiness, corresponding to zones of strong convective activities. Results also reveal considerable discrepancies among different cloud products over extended areas of north China and Mongolia. The Sichuan Basin is another region of large discrepancies among the four cloud products. Diurnal cycles of FY-2C cloudiness for the four seasons of a year are analyzed. The diurnal range of cloudiness is generally larger over land than over ocean. Remarkable diurnal variation is found over the Tibetan Plateau, the northern part of the Indian Peninsula, and central Asia where there is generally less precipitation. The peaks of diurnal cycle of cloudiness appear around local noon over the subtropical land, in the morning over the Indian Peninsula, and in the afternoon near the equator.