An Analytical Study Of The Stratosphere-troposphere Exchange Process Caused By A Tropopause Folding And Plateau Deep Convection

The data used in this paper are reanalysis data,meteorological observation data and satellite observation data.The methods used include synoptic diagnostic analysis,mesoscale numerical simulation,tropopause 3D-tag inspection algorithm,potential vorticity diagnostic equation.This paper studies a deep convective process under the background of tropopause folding(referred to as folding)over the Qinghai-Tibet Plateau on July 13,2016.Analyzing the causes of the two and the influence mechanism of folding on deep convection,verifying the influence of deep convective activity on the distribution of ozone,water vapor and other components in the UTLS area.The investigation showed that:(1)The deep convection in the eastern plateau is related to the upstream folding process.The cold vortex is stuck with the subtropical high.The high-altitude jet strengthens and then breaks,with the right side of the jet's entrance area divergeing and influencing on the convective.Unstable stratification,strong ascending motion and sufficient water vapor transport provide favorable conditions for the triggering of deep convection.(2)The tropopause folding occurs at the junction of the center of the north-south wind jet at high altitude,descending and moving eastward with the tilt of the wind field structure.Under the squeezing action of the center of the high-altitude north-south wind jet,the isentropic surface is inclined and the baroclinicity of the atmosphere is enhanced.The secondary circulation generated by the north-south wind high-altitude jet caused the tropopause to squeeze and sink from 150 hPa-120 hPa along the isentropic surface at the junction of the north-south jet to 400 hPa,which is the main weather condition for the formation of folds.(3)The tropopause folding provides a favorable stratification environment and dynamic thermal conditions for the occurrence and development of deep convection,and the release of latent heat from deep convection strengthens the local position vortex in the middle and high levels.The diagnosis of the local variation of the potential vorticity shows that the non-adiabatic heating of the convective precipitation process is beneficial to the increase of the local potential vorticity in the middle and high levels.(4)Deep convection causes an obvious exchange process in the upper troposphere-lower stratosphere,which affects the distribution of atmospheric composition in this region.The transport effect of deep convection penetrating the tropopause dilutes the ozone concentration in the local stratosphere,increases the water vapor and cloud ice content,and causes turbulence in the tropopause.(5)By using the Wei method's diagnosis of the mass exchange volume generated by crossing the tropopause shows that the mass transport caused by tropopause changes plays a decisive role in the total exchange volume,while the horizontal transport along the tropopause plays a leading role.