Analysis And Assesment Of Soil Moisture In China Based On The Situ Observation Data

Soil moisture is an important variable in the climate system. Understanding and predicting variations of surface temperature, drought, and flood depend critically on knowledge of soil moisture variations, as do impacts of climate change and weather forecasting. Recent modeling studies have demonstrated that a prior knowledge of land soil moisture state could, under certain circumstances, contribute significantly to the atmospheric predictability. Long-term consistent soil moisture datasets, however, are still very limited and, consequently, extreme or idealized soil moisture conditions are often employed in modeling studies. Such limitation has been addressed by various ongoing land data assimilation efforts, in which land surface model estimates soil moisture indirectly through their integration of observed precipitation and other forcing data.An accurate dataset of soil moisture is crucial for climatological analysis, for model development and evaluation, and for the correlation of remote sensing. Through collection, dissemination, and analysis of soil moisture data from around China, We used 226 stations out of 788 stations to analize the scales of temporal and spatial variations. Based on the result of analysis, we evaluate the reanalysis data of Interim in the European Center for Medium-Range Weather Forcasts (ECMWF), NCEP/NCEP Reanalysis (R-1), NCEP/DOE Reanalysis (R-2), and the modeling result of Variable Infiltration Capacity (Vic) by the forcing data of Global Land Data Assimilation System (GLDAS) in soil moisture trends for the top 10-cm and 50-cm soil layers. Land surface models, in general,do not capture the observed soil moisture variations when forced with either model-generated or observed meteorology.The spatial climate distribution of the soil moisture in China is shown in this study. The soil moisture in Inner Mogolia and North China is low, about 0.12cm3/cm3, the Northeast and Sortheast is higher, about 0.22 and 0.32 cm3/cm3. In the seasonl circle, the observed soil moisture in winter is highest in four seasons, and in summer is lower, in the spring and autumn is lowest. The result of Eof shows that there mainly are two anomaly parts. Yangzi and Huai River are positive anomaly area, Northeast is negative anomaly area. The two parts showed totally opposite change in time series.The comparison in the four soil moisture datasets is showed in the paper. ERA_Interim soil moisture data set is compared with soil moisture observations best. Results of three reanalysis and one land surface model modeling soil moisture (full field and anomaly) as compared to observations will be presented. The persistency decay of soil moisture derived from ERA_Interim and observation datasets will be discussed as well.The result of NASA/AMSR-E is improved by combine the modeling result of CLM and the CDF method. The result is better reflect the soil moisture data by compared it to the observation data in Inner Mogolia and Henan provice.