The Spatial-temporal Variation And Prediction Method Of Soil Moisture In Northeast China

Based on the wetness of the climatic background, the spatial andtemporal variations of soil moisture in Northeast China and its key impactfactors are analyzed, by using method of the combine of cluster analysisstatistic test (CAST) and rotated principal component analysis (REOF). Inaddition, the forecast equation of soil moisture in different areas ofNortheast China would be established. The results show that:(1) The climate conditions with soil moisture are analyzed by aridity,which has a great association with evapotranspiration （ET） andprecipitation. The variations of precipitation and ET lead to the change ofaridity, which cause the climate a drying trend in west area. (2)Soil moisture of Northeast China can be divided into five areas. Thefirst area is located in the north part. The second area is located to the westof Great Khingan. The third area is located in the south of Songliao Plain.The fourth area is located around the Nen river and Songhua river. And thelast area is located in the southeast part. The soil moisture shows an upwardtrend in middle area and a downward trend in other areas in NortheastChina, but the west area has the largest decline. From the verticaldistribution, the range of soil moisture in20-30cm layer is larger than in the0-10cm and10-20cm layer expect for the northeast area. In addition, thesoil moisture of Northeast China has a periodic variation of about3-5years,which is mostly about5years.(3)Based on the observation data from1981to2010, the temperatureand precipitation of Northeast China can be divided into different divisions,which are similar to the soil moisture, especially the precipitation. Thespatial variations of precipitation almost coincide with the soil moisture, sothe precipitation does greater contribution to the variation of soil moisturethan the temperature. There has an upward trend for temperature and a downward trend for precipitation in Northeast China. But the regions ofvariation are greater in west area and smaller in north area. The temperatureof Northeast China has a periodic variation of about3-5years, which ismostly about3years. The precipitation has a periodic variation of about5-6years. The variation of soil moisture is closely related to precipitationand temperature. The decline of soil moisture in west area is caused by theobvious decline of precipitation and climate warming in this area. The raiseof temperature in middle area is smaller, but the precipitation is almostunchanged, so the variation of soil moisture is smaller.(4) The significant impact factors of soil moisture are different indifferent areas. But correlation is evident when compared with last dekadprecipitation and soil moisture, the correlation coefficients all throwconfidence tests of0.05. In addition, the soil moisture in southwest area isheavily influenced by the sunshine duration but the temperature, whosecorrelation coefficient is below0.05. The forecast equations of differentareas are established with the data from1981to2007and checked with thedata from2008to2010. The average relative errors in each area are7.47%, 11.59%,12.34%,13.67%and12.16%respectively. From the comparisonbetween predicted and observation values, the real situations of soilmoisture can be showed by this predicted value.