Analysis Of The Characteristics Of Soil Moisture In The Qinghai-Tibet Plateau And Its Influence On Land Surface Processes

Based on the monthly assimilation data of GLDAS_Noah 2.0 from 1950 to 2009,the basic state distribution of soil moisture in the surface layer(0-10cm),shallow layer(10-40cm),middle layer(40-100cm)and deep layer(100-200cm)of the Qinghai-Tibet Plateau and the change trend of its basic state are analyzed by statistical method.The changes of soil moisture in different layers of the whole and different regions of the plateau are deeply understood.Meanwhile,the effects of soil moisture at different levels on sensible heat flux,latent heat flux and radiation flux were analyzed by using land surface parameters in GLDAS data based on differential synthesis analysis.The results show that:(1)In the past 60 years,the soil moisture of each layer decreases gradually from south to North in space,but there is an extreme center in the middle and deep layers of the plateau.The difference of soil moisture in each layer of the mid-eastern parts of the plateau(excluding the deep and middle layers)is the vertical distribution of “wet upper and dry lower”,and the difference between the central and western regions is the vertical distribution of “wet lower and dry upper”,with a trend of strengthening.The first mode of soil moisture in each layer of the summer plateau shows a southwest-north-east reverse type distribution,and as the depth increases,the zero line moves to the northeast.(2)In the past 60 years,the interannual variation of soil moisture in the main layers of the summer plateau is obvious,except for the deep layer,which has a significant downward trend.The early stage is higher and the later stage is lower,while the deep layer is generally opposite.The interannual variation after removing the linear trend,except for the deep layer,decreases in the central region with the increase of soil level,and increases with the increase of soil level in the central and eastern regions.In addition,in addition to the tendency of deep soil moisture to become larger in the middle of the plateau,the trend of soil moisture in each layer is mainly distributed on the plateau to become smaller.(3)The sensible heat flux,the net short-wave radiant flux,the soil heat flux and the ground temperature difference are all spatially small in the west and the east,and the overall interannual variation has a significant downward trend(except the soil heat flux);The amount and net long-wave radiant flux are spatially small in the east and west.Before the 1980 s,the interdecadal changes were dominant.After the 1980 s,the interannual variations were dominant.(4)When the soil moisture in the middle layer and above is too large,the temperature difference in the western part of the plateau is small,resulting in a small sensible heat flux,and the net long-wave radiation is too small,so the net radiation is small,and the temperature difference in the northern and northeastern parts of the plateau is biased.Large,resulting in a large sensible heat flux,the net short-wave radiation flux is too large,so the net radiation is too large.When the soil moisture in the shallow layer and above is too large,the transpiration of the eastern part of the plateau is strong,the latent heat flux is too large,and the sensible heat flux is small(consistent with the EF).When the deep soil moisture is too large,the impact on each land surface parameter is relatively small.