淮河流域土壤湿度的分布特征和记忆能力分析

The Spatio-Temporal Characteristics of Soil Moisture and Its Memory over Huaihe River Basin

利用1992—2013年包括台站观测在内的五套土壤湿度资料,分析了淮河流域土壤湿度的时空分布特征和记忆能力,并验证了卫星遥感和再分析资料在淮河流域的适用性。结果表明,台站观测的土壤湿度在淮河流域表现出北干南湿的空间特征,其年际变率呈现西大东小的特点;总体说来,欧洲中期天气预报中心最新的陆面再分析数据集(ERA5-Land)的土壤湿度在时空分布和演变上与观测最为接近,此外通用陆面模式CLM4离线模拟得到的土壤湿度的年际变化与台站观测也较为接近。流域土壤湿度的记忆能力随时间尺度的增加而增加,但这种差异主要体现在土壤浅层,到40~50 cm深度记忆能力随时间尺度的变化已相对较小;土壤湿度的记忆能力还具有较强的季节变化,流域平均土壤湿度的记忆能力在秋末、冬初较大,而在夏季较小,其中CLM4以及耦合CLM4的IAP大气环流模式模拟的土壤湿度记忆能力的季节循环与台站观测较为接近。就土壤湿度记忆能力的空间分布而言,不同资料均呈现出记忆能力在流域西北部较强,而在南部区域较弱的特点,且这种空间差异在秋季最为显著。

Using five soil moisture data sets of,including the station observation during 1992−2013 over Huaihe River Basin(HRB),the spatio-temporal characteristics of soil moisture variation and its memory are analyzed,meanwhile,the remote-sensed and reanalysis soil moisture dataset are also evaluated against the observation.Based on the station observation,it is found that the observed soil moisture is relatively dry in the northern HRB,and wet in the southern HRB,with stronger inter-annual variability in western HRB and weaker variability in eastern part of the basin.Generally,the latest reanalysis soil moisture,from European Centre for Medium-Range Weather Forecasts(ERA5-Land),agrees well with the station observation in both spatial distribution and temporal variation,and the community land surface model(CLM4)can well reproduce the observed inter-annual variation of soil moisture when forced with observed meteorological variables.The longer memory of soil moisture can be found with increased time scale in surface soil layer,but this enhancement of memory with time scale becomes weak in deeper soil layer,like 40−50 cm.The soil moisture memory also shows strong seasonal variation,with longer memory in late autumn and early winter,and weak memory in summer,and the observed seasonal cycle of soil moisture memory can be well reproduced by both the standalone CLM4 simulation and the IAP atmospheric general circulation model coupled with CLM4.The spatial difference of soil moisture memory can be found for ERA5-Land,CLM4 and IAP-AGCM4.1,with longer memory in the northwest part of HRB and weaker memory in the southern HRB,and the regional contrast of soil moisture memory is the most significant in autumn.