Variation Characteristics of Soil Temperature & Moisture and Air Parameters in the Source Region of the Yellow River

The source region of the Yellow River (SRYR) located in the northeast of the Tibetan Plateau, is the crucial water conservation area. Soil temperature & moisture variations and associated climate effects have important implications to the change of runoff. Three kinds of frequently used reanalysis datasets, ERA-Interim, CFSR, and JRA-55 are tested using field observations of Maqu Soil Temperature & Moisture Network so as to find the optimal one for SRYR. Combining with observations of Maqu Station, the climate changes in recent 35 years and the temporal variation of soil moisture & temperature are analyzed. In addition, their spatial variations are depicted by reanalysis datasets and CLM4.5(Community Land Model 4.5). Main results are as follows.CFSR is the best dataset to depict the soil moisture variation, and ERA-Interim is better on soil temperature, while JRA-55 is unsuited. Soil temperature has an indication to the climate change, but its response is less significant than air temperature. Soil moisture has an increasing trend, because freezing time becomes shorter and melting time is extending. Air temperature, soil temperature & moisture, except for precipitation, have abruptions in the last 35 years. Air temperature starts to abrupt during 1997-2000, after that it shows significant upward trend. Precipitation decreases from 1987 to 2004 and increases after 2005. Abrupt change of soil temperature takes place during 1985-1986, and beyond the belief line after 1994 with prominent rising. It means soil temperature is more sensitive than air temperature to climate warming. Soil moisture has an upward abruption in 2002. Soil temperature & moisture in 10 cm depth become warm and dry in recent years. Lakes and the Yellow River are the cold and wet centers in warm season, and turn warm and dry in cold season. CLM4.5 has high simulation accuracy, and is capable of describing detailed changes of soil in SRYR. All in all, it is better than reanalysis dataset in simulating the spatial variation of soil temperature & moisture, but still has a long way comparing with observations.