The Characteristics Of Soil Temperature Variation In China In Recent 50 Years And The Correlation Analysis Between The DGAT And Atmospheric Circulation Anomaly And Precipitation In Summer

Based on the data of monthly mean soil temperature in the depth of 0.8m from 532 stations in 1954-2001, the characteristics of the soil temperature variation over different areas in China are analyzed. The results indicate that in recent 50 years, the annual mean soil temperature experienced a cooling period, a relative cold period and a warming period. In Northeast China, soil temperature obviously increases after 1990s, while in the eastern part of Southwest China, soil temperature exhibits decreasing tendency. In around 1980, the eastern part of the Tibetan Plateau experienced a climatic jump that is featured by the decrease of soil temperature. In every area, Soil temperature interdecadal variation in winter is different from other seasons, while interannual variation in spring is the most obvious.Meantime, the data of monthly mean ground temperature in the depth of 0cm and air temperature from 695 stations in 1961-2000 are used to calculate the differences between ground temperature and air temperature (DGAT). The distribution of the DGAT in space-time and the correlation between the DGAT and the intensity and location of subtropical high in the western Pacific are analyzed. Then, the index of the DGAT in spring is defined and the relations between the index and the atmospheric circulation anomaly in the same term and the precipitation in summer and the summer monsoon interdecadal variation are analyzed. The results show that firstly, the value of the DGAT is positive all over the country except for the DGAT in Northeast China in winter and there are the different space-time distributions of the DGAT in different seasons. Secondly, the correlated distribution of the positive-negative dipole between the DGAT from March to June and the area of subtropical high in the western Pacific indicates the reverse trend of the zone differences of the DGAT. Thirdly, the interdecadal variation of the index of the DGAT is obvious and there is a corresponding correlation between the index and the atmospheric circulation anomaly in the same term. Fourthly, the positive correlations between the index and the summer precipitation in the middle and lower of the Yangtse Rive, the eastern of the Inner Mongolia and the SinKiang are evident. The interdecadal variation of the index of the DGAT corresponds to the summer monsoon interdecadal variation.