Study On The Characteristics Of Atmospheric Precipitation Change And Its Influence Mechanism On The Qinghai-Tibet Plateau

Utilizing the ERA-Interim monthly reanalysis data of 1979~2015 and using linear tendency estimation,EOF analysis,mutation test,climate tendency rate,correlation analysis and other statistical methods,as well as water vapor budget equation and water vapor transport equation.First,the atmospheric precipitable water over the Qinghai-Tibet Plateau in 1979~2015 was calculated and the spatial distribution of atmospheric precipitable water,the tendency of climate and the characteristics of interannual and annual change are analyzed by stratification.Then the mechanism affecting the precipitable water over the plateau were studied and the variation characteristics of water vapor divergence and water vapor advection were analyzed.Finally the characteristics of water vapor transport over the Tibetan Plateau were studied from the point of view of stationary wave and transient wave.The resulting conclusions are as follows:1.The center position and regional difference of spatial distribution and its climate tendency rate at different layers are not the same,also there are obvious seasonal differences.Through inspection we found that 1995 is the abrupt year.The annual average,spring,summer and autumn value of atmospheric precipitable water before abrupt is higher than that after abrupt change year,however,in winter,the value of atmospheric precipitable water after abrupt is higher than that after abrupt change.Before abrupt change,annual average and seasonal average of atmospheric precipitable water are rising trend,after abrupt change,expect winter is downward trend,the other seasons are upward trend,the rising trend rate before abrupt change is faster than that after abrupt change.From EOF analysis of the first three modes can be known,The spatial distribution of atmospheric precipitable water contain the consistent positive or opposite pattern,and the two spatially-opposite patterns in the East the West and the North and the South.2.Study the influence mechanism of atmospheric precipitable water,the result shows : Water vapor convergence and divergence and water vapor advection have a better correlation with atmospheric Precipitable Water.The overall spatial distribution characteristics of water vapor convergence and divergence are low-layer convergence and upper-layer divergence;in the whole layer and surface layer,the eastern part of the plateau is moist advection,and the rest of the region is dry advection.In the middle layer,the moist advection region is large,and there is almost dry advection in the upper layer.The inter-annual variation of water vapor convergence and divergence shows an increasing trend,in which the increasing trend is the most obvious in the whole layer,surface layer and the middle layer;and the inter-annual variation of the water vapor advection shows a downward trend in the whole layer and the other three layers,most obvious in the middle and upper-layer.With the increase of altitude,the center of climate tendency value of water vapor convergence and divergence also changes;the spatial distribution of climate tendency of water vapor advection is from positive west and negative east to negative whole,and the regions with the largest decreasing trend are the west and southeast part of the plateau.3.The characteristics of water vapor stationary wave transport and transient wave transport in Qinghai-Tibet Plateau are as follows: The spatial distribution of water vapor flux divergence caused by stationary wave appears as low-level convergent and high-level divergence,and the divergence of water vapor flux caused by transient waves is dominated by water vapor divergence in the plateau main area.The strongest intensity and volatility are in summer according to the data.The steady wave transport of water vapor indicates that the zonal direction of the plateau is mainly affected by both the east and west winds.As the altitude increases,it is mainly affected by the westerly wind transport,and the main trend is southerly wind transport.The interannual variation shows that the zonal transport of the annual average steady wave is westerly.Most of them are carried by east wind in winter,mainly by easterly wind in summer,and mainly by south wind in meridional direction throughout the year and winter.The transient transmission of water vapor shows that the plateau zonal westerlies are mostly transported by the westerly winds;the meridional winds are transported by the south winds.It is known from the interannual variations that the whole year and the winter are mainly transported by the westerly winds;the meridional direction,the year and the winter wave are mostly southwards.The wind transports the south wind throughout the summer.The water was mainly from water vapor stationary wave transport,transient wave transport mainly transport water vapor from the low latitude to high latitude area.