The Temporal And Spatial Change Of Sensible Heat Fluxes Over The Tibetan Plateau And Its Impact On Regional Summer Precipitation In China

Energy,matter,and momentum exchange have a considerable effect on global atmospheric circulation and climate fluctuations when it interacting with ground gases,among of which,in the near stratum,the sensible heat fluxes interact with the atmosphere in the form of turbulence.As the average elevation of the Tibet Plateau is greater than 4000 meters above the earth is known as the "third pole",its standing in the high-altitude strong heat heating called heat-driven pump.The heat of the TP is a fatal factor in the Asian monsoon alternation,and it is undoubtedly important for the precipitation in East Asia.At the same time,during the monsoon transition,the sensible heat fluxes over the TP are the vital factor in the heating TP and its surrounding areas,which play an important role in the prediction of summer precipitation:in China.According to the difference of vegetation coverage on the underlying surface of the TP,we divided the TP whose altitude is 3000m into seven sub-regions(area A-G).At the same time,by utilizing the observational data of 78 sites from the TP,the observation data of 830 stations nationwide and the global 17-layers data provided by NCEP(R2),the sensible heat fluxes over the TP and each district were calculated.By means of wavelet analysis,correlation analysis,synthetic analysis and EOF analysis,the temporal and spatial distribution characteristics and variation regulations of sensible heat flux over the TP were studied.What's more,the relationship between the sensible heat flux in April and the summer precipitation in China as well as the relationship between the summer precipitation in the south of Yangtze River in China were also studied.Temporal and spatial variation of sensitive heat flux over the TP,the annual average sensible heat flux,spring and summer,the heat flux cycle are 3-4a,while the season of autumn and winter are 2-3 a.The strongest heat center which includes annual average and seasonal average emerges in Himalayan region.However,the weakest value appears in area A of western TP.Its distributions are uniform during in spring and autumn,and emerges conspicuous gradient distributions in summer and in winter.Its directions,in summer,are from east to west,while the gradient is oppose in winter.Seasonal transformation of the sensible heat flux is jointly determined by the variation of the 10 meter extreme wind speed along the northward and southward and the difference between ground surface temperature and atmospheric temperature.Relationship between sensitive heat flux over the TP and precipitation in the South of the Yangtze River is negative correlation.In April,the Himalayan area(area E)is a vital area influencing the summer precipitation in the south of the Yangtze River.The sensible heat flux over the key areas in April and the summer precipitation in the south of the Yangtze River have the opposite trend,that is,negative correlation,The main period are 4a and 8a sub-period.In 1998,2011,respectively,before and after emerge a turning point.As the sensible heat flux over the critical area of TP is weak,the area of the south of the Yangtze River is in front of the deep trough.With the shear line system,the baroclinicity is very strong and the relative humidity is very high,which jointly contribute to the precipitation.On the contrary,it will not conducive to precipitation.