利用CFSR资料分析近30年全球云量分布及变化

在利用MODIS卫星的云产品资料对CFSR(Climate Forecast System Reanalysis)再分析资料云产品质量进行检验评估的基础上,采用CFSR资料对1979—2009年全球总云量及低、中、高云量的平均分布及其随纬度的变化进行了分析;用经验模态分解(EMD)方法分析了近30年全球云量的变化趋势,结果表明:(1)全球近30年平均总云量约为59%,全球总云量及低云量、中云量都有明显的纬向分布特征,全球总云量有3个峰值带和3个低值带。(2)低云量的海陆分布差异较明显,陆地上的低云量明显低于海洋上的,除了两个极圈附近,南半球各纬度的低云量都比北半球相应纬度上的都要多;高云量的高值、低值中心均集中在赤道附近到南、北半球30°之间的中低纬度,并且低值中心主要分布在大洋的东部。(3)总云量的总变化趋势为增长,具体表现为随时间呈现先略减少后大幅增加趋势,其突变点大致在1993年,在1993年之后,总云量显著增多。低云量和高云量均呈现增长趋势,中云量则相反,呈减少趋势。低云量增幅最明显,接近2%,中、高云量则增减幅度较小。

Analysis of Global Cloud Amount over the Past 30 Years Based on CFSR Data

Based on the verification and evaluation of the quality of CFSR (Climate Forecast System Reanalysis) cloud amount reanalysis data by satellite remote sensing data MODIS, we analyze the average distribution of global total and low, middle, high cloud amount from 1979 to 2009 as well as the cloud amount variation along the latitude. Also, by using empirical mode decomposition (EMD) method, we analyze the change trend of each cloud amount in the recent 30 years. The results show that: (1) the global average total cloud amount in recent 30 years is about 59%, the global total and low, middle, high cloud amounts have obvious zonal distribution characteristics, and there are 3 peak value zones and 3 low value zones for the total cloud amount. (2) The difference of land sea distribution for low cloud amount is obvious and the amount of low cloud over the land is significantly lower than that over the ocean. Except for the two polar regions, the amount of low cloud in the Southern Hemisphere is more than that of the corresponding latitudes in the Northern Hemisphere; the locations of maximum and minimum of high cloud amount are between the mid low latitudes (30°) of Southern, and Northern Hemispheres respectively. In addition, the low value center mainly distributes in the eastern ocean. (3) The variation of total cloud amount is in an increasing trend, and it is specificly displayed as skyrocketed after a slightly decrease with the time. Its jump point year is around 1993, after which total cloud amount increases significantly. Low and high cloud amounts show a decreasing trend, in contrast, middle cloud amount is decreasing. Low cloud amount increases the most by nearly 2% while the change of high cloud amount is smaller.