Spatial And Temporal Variations Of Soil Temperature At Shallow In Heilongjiang Province

Soil temperature is one of the factors that have a important impact to climate change. Soil temperature at all layers reflect the level of surface heat amount at earlier stage, will not only change the regional climate conditions, but also have some impact to large-scale circulation, and related to crop growth and yield directly. The analysis of spatial and temporal distribution about soil temperature anomaly and the relationship of soil temperature and other meteorology-cal factors, is very important to understand the character and mechanism of land-atmosphere interaction, causes of climate change, the soil temperature on the response of climate change, and provide scientific basis for long-term forecast. Heilongjiang province is located in the high latitude, and is the sensitive area of climate change. Its climate change is effected by global warming, and also own regional characters. Seasonal freezing and thawing make the analysis about soil temperature more complex. Using 0,5,10,15 and 20cm daily mean soil temperature, air temperature and precipitation data from 16 weather stations in Heilongjiang province, we studied spatial and temporal distribution of soil temperature, the statistical methods include spatial analysis, linear trend and correlation analysis.The main results are as follows:As the latitude increased, the annual mean surface temperature of Heilongjiang Province was decreased from south to north, the variation of isotherm line for most of the region was paralleled with the latitude variation, the isotherm line of eastern region was distributed with the direction of longitude line. In addition to the summer, the variation of the mean surface temperature for other three seasons showed the similar variation characteristics of annual mean surface temperature. Five averages geothermal of May to September had the almost same spatial distribution pattern, the variation of isotherm line for some areas was distributed along the direction of latitude line, the variation of isotherm line for eastern region was distributed along the direction of longitude line.Just for one year, the surface temperature for each site and Heilongjiang Province had the obvious variation of sine functions, the difference among changes during the year for different sites was significant. The annual mean surface temperature of Heilongjiang Province showed the rapid heating process from May to July and slow cooling process from July to September. The vertical gradient of soil temperature decrease gradually from July to September.The surface temperature of Heilongjiang Province and all sites showed increasing trend for 41 years, the annual mean surface temperature of Heilongjiang Province was increased by 0.039℃/a, the linear trend was 0.050,0.027,0.020,0.060℃/a for spring, summer, autumn and winter. The ground temperature was overall lower from the early 1960s to the late 1980s. The surface temperature Significant warmed from 1988, and the surface temperature of period from the late 1980s and throughout the 1990s was relatively high for 41 years. Five averages geothermal of Heilongjiang Province and all sites from May to September showed the warmed trend from 1960 to 2000. Climate trend rate at depth of 0cm was the highest of five depths and the value was 0.030℃/y; the difference among warmed rate of mean soil temperature at depth 5-20cm was not obvious.In winter, the spatial distribution pattern of surface temperature and air temperature had the highest similarity, however, which had highest difference in summer. The spatial distribution pattern of surface temperature was mainly affected by the high or low and transformer of temperature in winter, The influence of precipitation on geo-temperature space distribution was mainly focused on summer, and the effect was notable in southern area near the sea. There was a notable positive correlation relationship between average temperatures and surface temperature of year and each season, the correlation coefficient is the largest in winter and lowest in summer. There was a negative correlation relationship between precipitation and geothermal temperature, the value in summer was up to -0.430, More rainfall of year common corresponds to lower temperature of the surface temperature; There was a positive correlation relationship between rainfall and surface temperature. The effect of air temperature and rainfall on geothermal temperature was decreased as the soil depth increased.