基于CloudSat和ISCCP资料的中国及周边地区云量分布的对比分析

利用2006年7月至2007年6月的CloudSat 2B-GEOPROF-LIDAR产品资料和国际卫星云气候计划(ISCCP)D2月平均云量数据, 统计分析了中国及周边地区午间、凌晨年平均总云量的分布特征, 并对两种探测手段得到的年平均总云量及其昼夜变化进行了对比分析。结果表明, ISCCP与CloudSat总云量的分布形势在午间和凌晨均具有较好的一致性, 即相对多云与少云中心的位置吻合较好。但是, 两种资料得到的总云量在量值上存在一定差异。对于整个研究区域而言, 午间ISCCP较CloudSat平均总云量偏低8.9%, 凌晨偏低15.1%。除了中国北方少云带和日本岛以北海域等区域ISCCP云量高于CloudSat云量外, 其他区域ISCCP云量普遍低于CloudSat云量, 且在青藏高原、帕米尔高原、横断山脉、云贵高原以及印度半岛南端和热带部分岛屿等区域尤其显著。进一步对比表明, ISCCP与CloudSat云量差值总体上随CloudSat云量的增大而呈线性变化, 在CloudSat少云区ISCCP略有偏高, 而在多云区则显著偏低。此外, 对云量昼夜变化的对比分析发现, 青藏高原地区ISCCP云量昼夜变化量显著大于CloudSat。

Comparison of Cloud Amounts from ISCCP and CloudSat over China and Its Neighborhood

Using the CloudSat 2B-GEOPROF-LIDAR product data and the monthly mean data of ISCCP (International Satellite Cloud Climatology Project) D2 from July 2006 to June 2007, the distributions of annual mean total cloud amounts over China and its neighborhood were analyzed and compared at noon and wee hours, respectively. The results show that both the distributive patterns of cloud amounts agree well with each other, and the locations of the maximum and minimum from two kinds of data are close. However, there are some quantitative differences between the two kinds of observations, especially at wee hours. For the whole areas, the difference of mean cloud amounts between ISCCP and CloudSat is respectively -8.9% and -15.1% at noon and wee hours. The annual mean cloud amounts of ISCCP are generally less than those of CloudSat, except in the northern zones of China and the sea area lying to the north of Japanese islands. In addition, the differences of cloud amounts between ISCCP and CloudSat over the Tibetan Plateau, the Pamir Plateau, the Hengduan Mountains, the Yungui Plateau, the southern part of India peninsula and some islands in the Tropics are more significant. Furthermore, it is indicated that the difference of cloud amounts between ISCCP and CloudSat changes linearly with CloudSat cloud amounts increasing. The ISCCP cloud amounts are slightly higher in the case of low CloudSat cloud amounts, and remarkably lower in the case of high CloudSat cloud amounts. Finally, by comparing the difference in annual mean cloud amounts from ISCCP between daytime and nighttime with that from CloudSat, it is found that the disagreements are significantly larger over the Tibetan Plateau than the other areas.