基于CloudSat资料的东海及周边云层垂直分布特征

Characteristics of cloud stucture based on CloudSat data in the East China Sea area

利用2007—2010年CloudSat二级产品中的2B-GEOPROF和2B-GROPROF-Lidar数据,分季节、昼夜统计分析东海海区及其周边的云层频率、云层厚度、云层间隙等云垂直参数的时空分布特征,并利用EOF分解给出了云层出现频率的第一、二模态。结果表明:无论任何季节、昼夜,云层的数目与其出现的频率均成反比,即云层数越少出现的频率越高,出现最多的是单层云,年平均出现频率在60%以上;其次是双层云,年平均出现频率在20%～30%之间;出现三层云及以上的情况很少。云层数越多,底层云底高越低,顶层云顶高越高,每层云的厚度越薄,每层云之间云层间隙也越小。云的垂直结构受季节和地域影响较大。单层云频率月异常的第一、二模态分别反映了海陆下垫面不同的影响以及东亚大槽和西太平洋副高的影响,并均具有年变化。双层云第一模态则表现为在东海及其周边的绝大部分范围,春季出现的频率高,秋冬季出现的频率低,并也有年变化;而第二模态则无年变化。

Based on 2B-GEOPROF and 2B-GROPROF-Lidar data of CloudSat from 2007 to 2010, the spatial and temporal distribution characteristics of cloud layers frequency, thickness and rifts in clouds in the East China Sea Area under daily and seasonal time scale are analyzed using the EOF decomposition method.The results show that the numbers of clouds are inversely proportional to the clouds occurrence frequency at both seasonal and daily scale. The highest frequency of occurrence is a single layer cloud, followed by double layer cloud and four layer clouds. The more cloud numbers, the lower cloud base height. The higher cloud top height, the thinner the thickness of each cloud layer and layer of cloud gap. The vertical structure of cloud has an obvious seasonal and spatial features. The first and second mode of single layer cloud occurrence frequency reveals the different impacts of land and sea underlying surface, and the influence of East Asia major trough and west pacific subtropical high with annual variation features, respectively. The first mode of double layer of cloud occurrence frequency indicates the highest frequency of occurrence in spring and the lowest frequency in autumn and winter with annual variation features.