Spatial Distribution and Temporal Variation of Soil Moisture over China Part I: Multi-data Intercomparison
中国土壤湿度的分布与变化 I. 多种资料间的比较

Soil moisture is one of the most important factors affecting the climate.However,deficiency of data coverage has limited the progress of soil moisture studies in terms of its role in climate.In this paper,four sets of widely-used soil moisture data are collected,i.e.the European Centre for Medium Range Weather Forecasting(ECMWF) 40-year reanalysis(ERA40),the National Centers for Environmental Prediction/National Center for Atmospheric Research(NCEP/NCAR) reanalysis data,Global Soil Wetness Project product,and the output of the Community Land Model forced by observational atmospheric conditions.Qualities of these four sets of soil moisture data over mainland China are evaluated by using observational evidences.The results show that the spatial patterns of the four soil moisture data sets generally agree well with the observation.The GSWP2 data are the best one among four datasets in producing the observational pattern,i.e.,the soil moisture gradually increases from northwestern to northeastern and southeastern China,with northeastern and southern China being wet,northern and northwestern China being dry.The seasonal cycle of GSWP2 soil moisture is also better than any of the others.The ERA40 data have the highest correlation with the observation in producing the interannual variability of the soil moisture.All data show significant positive correlation between the precipitation and later time soil moisture,while no significant correlation can be found between precipitation and preceding soil moisture.The relationship between the soil moisture and air temperature is complex and the results are region-dependent.