The Distribution Characteristics Of Soil Temperature In The Qinghai-Tibet Plateau And Its Influence On The Thermal Effect Of The Plateau

As an important parameter to characterize soil thermal conditions,soil temperature is the main factor affecting the atmosphere by the land surface.It can influence climate change by affecting changes in surface energy and water budgets.This paper used the newer,continuous,high-resolution(0.25°×0.25°)GLDAS Noah v2.1 land surface model data,using linear propensity estimation,correlation analysis,empirical orthogonal function decomposition,and sensitivity factors.The following important conclusions were drawn:(1)The characteristics of soil temperature change in the The Tibetan Plateau wereanalyzed by linear tendency estimation,correlation analysis and empiricalorthogonal function decomposition.The results showed that the average soiltemperature in the plateau area was lower than that in the surrounding area,andthe north was lower than the south.EOF analysis of the first mode of soiltemperature showed obviously uniform temperature increasing type over thewhole region.Four layers of soil temperature rise year by year.The warming trendin the plateau was stronger than that in the surrounding areas,and the main part ofthe plateau was warmer in the west than in the east.As the depth increases,thewarming trend gradually decreased.(2)The spatial distribution of annual average latent heat flux over the Tibetan Plateauwas low in the northwest and high in the southeast.The sensible heat flux was justthe opposite.The latent heat flux and sensible heat flux formed a distinct thermalgradient in the northwest-southeast.The annual average surface heat flux had aweak negative area in the southeast corner of the plateau,and other areas werepositive.The four-season spatial distribution characteristics of latent heat flux,sensible heat flux and surface heat flux have common characteristics:the largest insummer and the smallest in winter.The latent heat flux increased significantly at arate of 0.28(W/m~2)/year from 2000 to 2016.There was no obvious trendchange in sensible heat flux.The surface heat flux increased significantly at a rateof 0.03(W/m~2)/year.(3)The effect of soil temperature on heat flux:The effect of soil temperature on latent heat flux:The main part of the plateau hada significant negative correlation except for the high altitude area,and the rest ofthe area was significantly positively correlated.Soil temperature and latent heatflux were in the same increase and decrease year by year.The correlation between soil temperature and latent heat flux was best in autumn.The sensitivity factor of latent heat flux in response to soil temperature change was the largest,indicating that the change of soil temperature in autumn had the greatest influence on latent heat flux.As for the sensitivity factors of the whole year,spring and autumn showed a significant increasing trend,while the summer and winter sensitivity factors showed a significant decreasing trend.The effect of soil temperature on sensible heat flux:the correlation between soil temperature and sensible heat flux with the correlation between soil temperature and latent heat flux were opposite.The southwest hinterland of the plateau was significantly positively correlated.The hinterland of the plateau was negatively correlated.In winter and spring,as the soil temperature increased,the sensible heat flux decreased year by year.Summer sensible heat flux was significantly positively correlated with soil temperature.The summer sensitivity factor was the largest,the change of soil temperature in summer had the greatest influence on the sensible heat flux.The winter sensitivity factor was negative,additionally,the absolute value was the largest.The influence of soil temperature on sensible heat flux in winter was counterproductive as the reaction was the strongest.As for the sensitivity factors of the whole year,autumn and winter showed a significant increasing trend.The sensitivity factor of the whole year and autumn was positive,and the influence of soil temperature on the sensible heat flux increased year by year.The sensitivity factor in winter was negative,and the effect of soil temperature on the sensible heat flux was weakened year by year.The effect of soil temperature on surface heat flux:the main part of the plateau showed a significant positive correlation,and the northern Tibetan plateau had the most significant correlation.There was a significantly positive correlation between areas along the southern edge of the plateau in the Himalayas.The four layers of soil temperature and surface heat flux featured the same trend of changes.The correlation between soil temperature and surface heat flux in spring was the most significant.The sensitivity factors in spring,summer,autumn and winter were reduced in turn.The sensitivity factors of spring and winter showed a significant decreasing trend,while the sensitivity factor of winter had the largest annual rate of change.