CMORPH卫星降水数据在中国区域的误差特征研究

空报数据和漏报数据是高时空分辨率卫星降水产品误差的重要表现形式,研究漏报和空报数据的特征对于改进降水反演算法、提高卫星降水数据的质量具有重要意义。通过对2009年6~8月中国区域内的CMORPH卫星数据(Climate Prediction Center Morphing)与观测站点逐小时降水数据分析,发现CMOPRH数据中的漏报数据和空报数据存在以下特征:①CMORPH数据中空报数据远远高于漏报数据,导致CMORPH数据模拟的降水面积要高于实际降水面,表明空报数据对CMORPH精度的影响要大于漏报数据;②当降水量小于5 mm时,CMORPH的空报率随着降水量的升高呈现出非线性的下降趋势,经过二次项拟合之后的相关系数达到0.99以上;③CMORPH中空报降水数据的面积与总降水面积之间存在很强的正相关性,二者在6~8月的相关系数分别达到0.9133、0.9474和0.9482,因此可以通过CMORPH数据的总降水面积对空报降水面积进行估算;④从CMORPH空报率的空间分布上看,我国东南沿海以及东北地区的空报率较低,而西北、青藏高原地区的空报率最高。

A Research into the Characters of CMORPH Remote Sensing Precipitation Error in China

The missed and false alarmed precipitation is the main drawback of high-resolution satellite precipitation estimation.In this study,the missed and false alarmed of CMORPH(Climate Prediction Center morphing) with spatial resolution of 0.1°×0.1°and temporal resolution of an hour were calculated by comparing with ground observations.Then the false alarmed ratio was calculated and compared with precipitation ratio and precipitation areas.The results show that:① There is a huge number of false alarmed data in CMORPH which is much more than the missed data,and leads to the precipitation areas of CMORPH enlarged compared with ground observations;②The relationship between the false alarmed area and the total precipitation area is very strong in June,July and August,and the correlation coefficients are 0.9133、0.9474 and 0.9482 respectively.So the area of false alarmed can be estimated by the total precipitation area of CMORPH;③ When the rainfall is below 5mm,the false alarming ratio is related to the rainfall value.As the rainfall value increasing,the false alarming ratio tends to decline;④ The spatial distribution of the false alarming ratio present obvious regional characteristic.The false alarming ratio in southeast,northeast is the lowest,while in the west of china is the highest.All of the conclusion above can be used as the scientific basis in building correction model of CMORPH.