三套再分析降水资料在中国区域的对比评估

Evaluation of Three Reanalysis Precipitation Datasets in China

利用实测资料对NCEP-1、ERA-40和20CR再分析降水资料在中国范围内均值、年际变化、相关性和长期趋势等方面进行比较评估。结果表明,平均而言ERA-40年降水量和实测值最为接近,而20CR和NCEP-1年降水量明显偏多,三者差值百分比分别为-1.3%,55.0%和36.9%三种再分析降水偏差最大区均出现在西南地区,最大偏差值都在600 mm以上;年际变化上,ERA-40和NCEP-1自20世纪70年代中期开始年降水差值百分比出现一定波动性,而20CR在整个研究时段年降水差值百分比基本稳定;三套资料和实测资料的相关性具有明显的区域性特征,东部相关系数明显高于西部,值得一提的是ERA-40在大部地区的相关性好于其他两套资料;ERA-40和20CR则对大部分区域降水变化趋势的描述好于NCEP-1资料。

The NCEP-1, ERA-40, and 20CR reanalysis precipitation data were evaluated by comparing their means, interannual variations, linear trends, and correlations with the observations in China. The results indicate that on the average, the ERA-40 data agreed better with the observations than the other two reanalysis datasets although it underestimated precipitation slightly. Both the NCEP-1 and 20~CR data overestimated precipitation obviously, the percentage deviations of annual precipitation of the ERA-40, 20CR, and NCEP-1 from the observations over China were -1.3%, 55.0% and 36.9%, respectively. The maximum precipitation deviation usually occurred in Southwest China, with a value more than 600 mm. Percentage deviations of annual precipitation of the ERA-40 and NCEP- 1 showed some fluctuations since the mid-1970s while the 20CR＇s showed stability over the whole period. Basically, all three datasets well described the interannual variation of annual precipitation over China, but their correlations with the observations were usually better in the eastern China than in the western China. Of them the ERA-40 exhibited a better correlation in most of China than the other two datasets, and the ERA-40 and 20CR described trends of annual precipitation in most of China better than the NCEP-1.