Seasonal variability of cloud optical depth over northwestern China derived from CERES/MODIS satellite measurements

The seasonal variability of cloud optical depth over northwestern China derived from Clouds and the Earth＇s Radiant Energy System （CERES） Single Scanner Footprint （SSF） Aqua Moderate Resolution Imaging Spectroradiometer （MODIS） Edition IB data from July 2002 to June 2004 is presented. The regions of interest are those with Asia monsoon influence, the Tianshan and Qilian Mountains, and the Taklimakan Desert. The results show that the instantaneous measurements presented here are much higher than the previous results derived from International Satellite Cloud Climatology Project （ISCCP） D2 monthly mean data. Generally the measurements of cloud optical depth are the highest in summer and the lowest in winter, however, Taklimakan Desert has the lowest measurements in autumn. The regional variation is quite significant over northwestern China.     

基于ISCCP卫星资料的南中国海云量特征分析

为较准确地了解掌握可以反映南中国海天气和气候特征的云量分布演变特征,利用1999年1月至2009年12月的ISCCP卫星云量资料,通过物理量特征提取、对比分析等方法,研究了南中国海总云量及高、中、低云量的分布演变特征,以及其与其他海域各季节云量季节性变化特征。结果表明:南中国海低云量四季中均表现为由海区向沿岸递减,总云量和中、高云量夏秋季高于冬春季,低云量则相反。对于不同海域的云量细节特征要依据各季节大气和海洋环流变化来细致区分,这样有助于在掌握规律基础上有效制作海域上空云的预报。     

对云量的长程相关性研究

为了探索云量的变化规律, 利用去趋势波动分析(DFA)方法, 选取北京、上海、太平洋西部和太平洋东部等4个区域, 对ISCCP每3小时的云量时间序列进行了分析, 发现: 这4个区域的云量在大的时间尺度上存在幂律相关性, 即云量具有较强的长程相关性(或持续性); 西太平洋上空云量的长程相关性强于东太平洋上空和其他两个地区。还发现海洋上折点出现的时间迟于陆地上。     

Analyzing global trends of different cloud types and their potential impacts on climate by using the ISCCP D2 dataset

The International Satellite Cloud Climatology roject (ISCCP) D2 dataset is used to study the global distribution of low, middle and high cloud amounts and their rends of 1983-2001. Evidences have shown that global arming has accelerated over the past 20 a and the 1990s as the warmest decade in the instrumental records since 861. Trends of various clouds amounts over this period are nalyzed by employing the linear regression method. The esults show that global mean total cloud amounts, in general,have tended to reduce over the past 20 a. But there are lightly increasing by about 2% before 1987 and decreasing y about 4% since then. Cloudiness trends of both low and igh clouds decrease while increase for the middle cloud.And there exist remarkable discrepancies in different regions.The preliminary analyses suggest that it is likely that the loud change occurring over the past 20 a is a positive feedback to global warming.