The Temporal And Spatial Evolution Characteristics Of The Qinghai-Tibet Plateau Vortex And Its Possible Connection With Thermal Effects

Tibetan Plateau Vortex(TPV)is one of the major heavy rain systems in the plateau and surrounding areas during summer.On the basis of ERA-Interim daily reanalysis data from 1979 to 2016,through an objective identification of TPV and comparing with the TPV yearbook in certain years,a TPV dataset is built.Results shows that:The average agreement rate between the results of objective identification and the TPV yearbook is 66.2%;the frequency and the center height are significantly correlated to the TPV yearbook.Therefore,the objective identification method based on ERA-Interim data is scientific and feasible.During the past 40 years,the frequency of the all TPVs had increased significantly with an annual average of 56.3,a 10-year period,and a mutation at1986.Most TPVs are detected from May through August.The frequency of TPVs increased in spring and summer,and decreased in autumn and winter.The same diurnal variation of TPVs can be seen in all seasons,with an active period of nighttime and a weak period of daytime(the maximum at 20:00 and the least in 08:00).The center height of the TPVs was normally distributed;the duration decreased exponentially;the frequency,the center height and duration are stronger or longer in summer than in winter.The highest occurrence lied in the area of 33°-36° N,80°-90°E,with the axis at around 35°N and the center located in the eastern Nagqu and northern Ngari.The geographic distribution of TPVs.Divided by the season,except in autumn,the central TPVs are at most,and eastern TPVs are at least.Divided by the movement type of TPVs,the genesis of eastward-moving and quasi-stationary TPVs are mainly located in the middle or west of the plateau,and westward-moving TPVs are rarely generated in the west.Divided by the season and the movement type at the same time,in all seasons the eastward-moving TPVs are at most,the quasi-stationary TPVs are in second place,and the westward-moving TPVs are at least,even in winter there are no westward-moving TPVs occurred.The time distribution of the surface heat(SH).From 1979 to 2016,the annual and seasonal average surface sensible heat flux(SSHF)of the Tibetan Plateau(TP)all decreased in different degrees.and the trend of autumn and winter was stronger than that of spring and summer.There is a 3-5 year period in annaul,spring and summer mean SSHF,and in autumn there is a 2-3 year period.The surface latent heat flux(SLHF)are increased except in spring.There is a 5-year period of mean SLHF except in autumn.The spatial distribution of SH.Except in winter,the mean SSHF of the western TP is larger than that of the eastern TP,and the mean SSHF of northern is greater than that of the southern.The spatial distribution of SLHF is opposite to that of SSHF.SLHF of eastern TP is larger than that of the western,and SLHF of southern TP is larger than that of the northern.The spatial correlation of SH and the TPVs frequency.There is a positive correlation between SSHF and the TPVs frequency in the main body of the TP,and a negative correlation in the northern TP with low correlation coefficient.Except the westward-moving TPVs,the other TPVs are significantly related to SSHF in the Qaidam Basin,the Kunlun Mountains and the western Ali area in the northern edge of TP.All TPVs,eastward-moving TPVs and the quasi-stationary TPVs are positively related to SLHF over all plateau,and westward-moving TPVs is positively related to SLHF only in the main body of the Plateau.The time correlation between SH and the TPVs frequency.In the summer year,SH is more stronger,SLHF is more greater than SSHF,the TPVs frequency is more.In the winter year,SH is relatively weaker,SSHF is more greater than SLHF,the TPVs frequency is less.