CLDAS融合土壤相对湿度产品适用性评估及在气象干旱监测中的应用

基于2008—2017年全国自动气象观测站逐旬土壤相对湿度观测数据，综合评估中国气象局陆面数据同化系统（CMA Land Data Assimilation System，CLDAS）0～20 cm层融合土壤相对湿度产品在中国地区的适用性，评估表明CLDAS土壤相对湿度产品在中国东北、西北、江南大部及华南等地区存在较大系统性误差，总体上适用性较差。为消除CLDAS土壤相对湿度产品的系统性误差，采用回归订正法、7旬滑动平均订正法和临近加权前旬订正法对CLDAS土壤相对湿度产品进行误差订正处理，对订正结果评估发现：订正处理后CLDAS土壤相对湿度产品与站点观测的相关性显著增加，系统偏差基本消除，适用性明显提高，3种订正方法中临近加权前旬订正法的订正效果最优。最后，采用经不同方法订正后的CLDAS土壤相对湿度产品对2017年5月东北—华北地区一次气象干旱个例进行重现，对比验证表明：相对其他两种订正方法，经临近加权前旬订正法处理后的CLDAS土壤相对湿度产品能更为精准地重现2017年5月东北—华北地区气象干旱的落区和强度。〖JP〗

Applicability evaluation of CLDAS merged soil relative moisture product and its application in meteorological drought monitoring

Based on in-situ dekad soil relative moisture observations of automatic weather stations nationwide from 2008 to 2017, this study makes a comprehensive applicability evaluation of CLDAS (CMA Land Data Assimilation System) merged soil relative moisture product at 0-20 cm layer. The evaluation shows CLDAS soil relative humidity product has large systematic error compared with in situ observations in Northeast China, Northwest China, most areas of Jiangnan, and South China, so it generally has poor applicability. To eliminate the systematic error of CLDAS soil relative humidity product, the regression correction method, seven ten-day moving average correction method, and near weighted last ten-day correction method are used to conduct error correction. The evaluation of the correction result shows the correction of CLDAS soil relative humidity product makes a significant increase of its correlation with in situ observations, the systematic error is basically eliminated, and its applicability has significantly improved. Among the above mentioned three correction methods, the near weighted last ten-day correction method performs the best. Finally, the corrected CLDAS soil relative humidity products with the three methods are used to reproduce one meteorological drought case that happened in Northeast-North China in May 2017. The verification results show that compared with the other two error correction methods, the CLDAS soil relative humidity product processed by the near weighted last ten-day correction method can more accurately reproduce the area and intensity of the meteorological drought in Northeast-North China in May 2017.