TRMM和CMORPH卫星资料对三峡库区降水的评估分析

利用1998—2016年TRMM和CMORPH两种遥感卫星资料降水和同期三峡库区气象观测站数据,通过比较干、支流和远、近库区气象站点的降水变化和蓄水前后降水量、雨日、降水强度和频率等变化特征,分析评估了基于两种卫星遥感降水和测站降水的三峡库区局地降水变化。结果表明:库区TRMM和CMORPH卫星降水年际变化特征总体上与气象观测站相符,反演效果在日尺度TRMM略逊于CMORPH,在季尺度CMORPH略逊于TRMM;两种卫星资料对冬季降水反演效果都偏弱。三峡库区干流和支流站点的降水变化总体一致,干、支流各站点降水量均具有较强的年际变化特征。TRMM相比CMORPH更能重现干、支流测站降水的年际变化特征,CMORPH降水年际波动振幅总体上比测站偏大。蓄水前后时段(1998—2003年与2004—2016年)对比,从不同等级降水的强度和雨日、季节降水频率和总量等变化反演效果来看,CMORPH资料分布相比TRMM更接近测站的变化趋势,反演效果略优于TRMM;但两种卫星资料的降水频率和降水量分布与测站的误差在蓄水前后变化都不明显。此外,气象测站、TRMM、CMORPH资料都表现出蓄水后三峡远、近库区年降水量的比值呈平稳波动状态,表明三峡水库蓄水后附近地区降水没有明显变化。

Assessment of Precipitation in the Three Gorges Reservoir Area with TRMM and CMORPH Satellite Data

Based on the TRMM and CMORPH remote sensing satellite precipitation data from 1998 to 2016 and the observation data in the Three Gorges Reservoir Area in the same period, this paper evaluates the local precipitation changes in the Three Gorges Reservoir Area by comparing the precipitation changes of the main stream and the branch stream as well as the far and the near meteorological stations, and by comparing the characteristics of precipitation, precipitation days and precipitation intensity before and after impoundment. The results show that the interannual variation characteristics of TRMM and CMORPH satellite precipitation data in the Three Gorges Reservoir Area are generally consistent with those of meteorological observation stations. The inversion effect of TRMM on the daily scale is slightly lower than that of CMORPH, and that of CMORPH on the seasonal scale is slightly lower than that of TRMM. The inversion effects of both satellite data on winter precipitation are weak.The precipitation variations of the main stream and the branch stream stations in the Three Gorges Reservoir Area are generally the same, having strong interannual variation characteristics. Compared with CMORPH, TRMM can roughly reproduce the interannual variation characteristics of precipitation at the main stream and branch stream stations. The interannual fluctuation amplitude of CMORPH precipitation is generally larger than that of meteorological stations. Compared with the time period before and after water storage (1998-2003 and 2004-2016), the CMORPH distribution is closer to the variation trend of the stations than TRMM in terms of the inversion effect of the precipitation intensity, precipitation days, seasonal precipitation frequency and total amount of precipitation at different grades, and the inversion effect is slightly better than TRMM. However, the precipitation frequency and distribution of the two satellites are similar to observation. The errors of the stations do not change significantly before and after impoundment. In addition, the meteorological stations, TRMM and CMORPH data show that the ratio of annual precipitation in the far and the near reservoir areas of the Three Gorges fluctuates stably after impoundment, which indicates that there is no obvious change in precipitation in the vicinity of the Three Gorges Reservoir after impoundment.