GPCP和TRMM PR热带月平均降水的差异分析

A COMPARISON STUDY OF THE TROPICAL MONTHLY PRECIPITATION ESTIMATED BY GPCP VERSION 2 DATASETS AND TRMM PR OBSERVATIONS

中文关键词:  GPCP，TRMM PR，热带月平均降水

英文关键词:GPCP version 2 datasets, TRMM PR, Tropical monthly precipitation.

中文摘要:

      文中利用GPCP（Global Precipitation Climatology Project）和TRMM(Tropical Rainfall Measuring Missio) PR(Precipitation Radar)资料，分析了1998～2002年热带地区月平均降水的差异及其主要原因。结果表明，GPCP和TRMM PR资料能一致地反映热带降水的主要分布特征，但降水的强度和范围存在着差异；两种资料的差异与雨强有密切关系；平均而言，洋面上的降水差异（0.5 mm/d）大于陆地上的差异（0.1 mm/d）。微波发射信号（SSM/I E）的反演结果对洋面降水的高估和地面雨量计的缺乏，是造成两种资料间差异的主要原因。分析结果还表明，洋面上GPCP降水相对于PR降水的最大概率差异随雨强增大呈线性增大；陆地上这种差异则呈非线性关系。文中最后还利用最大概率函数对1979～1997年GPCP气候平均降水的误差进行了分析。

英文摘要:

      Tropical monthly mean precipitation estimated by the latest GPCP version 2 datasets and PR products in large time and space scales were compared and the major causes for the differences between them were investigated. After quantitatively analyzing the relations between the difference and the rain intensity, the results were employed to estimate the error of GPCP climatology precipitation from 1979 to 1997. Results shown that both of the two datasets present similar distribution patterns of long-time mean tropical rainfall but with differences in amplitude and range. In general, the average difference over ocean (0.45 mm/d) was larger than that of over land (0.08 mm/d), and it was the overestimation of rainfall by SSM/I E over ocean and the absence of rain gauge station in some area over land that lead the differences. It was found that the magnitude of difference is highly related to the rain intensity. The precipitation of PR with maximum PDF (Probability Distribution Function) is linear with the given rain intensity of GPCP over oceans, but the relation is nonlinear over land. The departure between them is obviously larger in ocean than that over land when the rain intensity is weaker than 5 mm/d. Almost all the differences over ocean are positive, but negative difference can be found over land when the rain intensity is weaker than 6 mm/d. Using the regression function of the maximum PDF, an error field of the GPCP climatological precipitation was established before 1998, The error estimated by this study has the same distribution pattern with those estimated by GPCP itself , but the former carries some new information. It determined not only the absolute value of the error, just as GPCP did, but also the sign of the error. Additionally, it showed that GPCP has underestimated the error come introduced by passive microwave precipitation retrieval over ocean.