CloudSat云底高度外推估计的可行性分析

云底高度对于全球辐射平衡以及航空飞行均具有重要影响。针对CloudSat与MODIS主、被动观测的优缺点,本文提出了利用MODIS云分类信息进行CloudSat云底高度外推估计的技术。首先使用MODIS和CloudSat数据,利用回归分析方法比较了基于云类型（CSAT）与基于距离（MSAT）的云底高度估计方法的优劣。此外,分析了中国及周边地区CloudSat各类云云底高度的均一性特征。最后,利用CloudSat各类云云底高度的统计特征,建立了一种基于云类型和距离权重的云底高度估计方法,并对该方法进行了验证和分析。结果表明,利用该方法得到的MODIS各类云云底高度估计误差的标准差均小于1.5 km,除了积雨云在观测点与待测点距离大于400 km的估计误差均值稍大于1.5 km外,各种情况下其他各类云的云底高度估计误差的均值均小于1.5 km。

Feasibility Analysis of Extending the Spatial Coverage of Cloud Base Height from CloudSat

The height of the cloud base has significant effects on the global radiation balance and the aviation. In allusion to the merit and demerit of active and passive observations, a technique of spreading cloud base height from CloudSat, using the MODIS classification, is advanced. Firstly, based on MODIS and CloudSat data, the method (CSAT) using satellite classification to extend the CloudSat data is compared with a traditional distance weighted approach (MSAT) using regression analysis method. Then, the uniformity of cloud base over China and its neighborhood is analyzed. Eventually, using the statistic features of cloud base heights for different cloud types from CloudSat, a method combining the MODIS classification with distance weighted to estimate cloud base height is established and validated. The result indicates that the standard deviations of cloud base height errors for all MODIS cloud types are totally less than 1.5 km, and the average values are also less than 1.5 km for all MODIS cloud types except cumulonimbus, of which the mean in the case of the distance between observed and predicted sites being greater than 400 km is slightly greater than 1.5 km.