Objective Identification Of Plateau Shear Line Based On Reanalysis Data

In order to objectively and efficiently calculate Tibetan Plateau shear line(TPSL),analyze the climatic characteristics of TPSL.Comparing the applicability of three sets of high resolution reanalysis data in common use in plateau area,selecting the CFSR reanalysis data as the basic data,according to the basic standard of artificial identification shear line and knowledge of computer geometry,defining objective identification standard of TPSL,comparative analyzing and verifying the objective identification 2005-2015 TPSL with TPSL yearbook,statistical analyzing TPV and TPSL's climatic characteristics of both concurrent number,generated sequence,and source in recent 12 years.At the last,it is calculated by NCEP/CFSR high-resolution reanalyzed data in 1979 to 2016,which the 38-years-long TPSL statistic database.Further,the climatic character of TPSL is found based on this database.The specific results are showed as follow:(1)In this paper,the method of objective identification TPSL is established,in the generation frequency,monthly distribution and other aspects of Yearbook statistical results are similar,is an effective and objective identification method, the eastern TPSL accounted for about 7 into,is a basic type of TPSL,the western TPSL accounted for about 3;transverse TPSL is far greater than the number of the vertical TPSL,the vertical TPSL accounted for only 3.9%.The objective identification TPSL method can identify TPSL efficiently and quantificationally,it provides a new way to research the TPSL.(2)The maintain time of TPSL is 6h usually,basing on total deformation?vertical vorticity?horizontal divergence to analyze the strength of the meteorological elements of TPSL,it indicates that the great value area of the meteorological elements strength appears in 94°E~95°E.Three physical strength rapidly decreases in 98°E.In winter,TPSL's main deformation is the deformation wind;in summer,TPSL's main deformation is rotating wind and convergence wind.Objective to identify TPSL in eastern area located at 31°N~34°N and 94°E~99°E, the western TPSL of high incidence area located at 34°N~36°N and 85°E~90°E.(3)The objective identification TPV were 45 at an average annual rate in the last 12 years,the TPSL were 48 at an average annual rate,about 30% TPV and TPSL occurred concurrently.The phenomenon of TPV and TPSL appears in the whole plateau.When the two appear together,TPSL usually takes place before the TPV. When TPV appears,TPSL will maintain for a long time,and whether there is TPSL,TPV's holding time remain unchanged.(4)In the last 38 years,the objective recognition of TPSL was generated about 1873,and 49.3 were generated annually.In the last 38 years,the formation ofTPSL showed a slow decreasing trend,and the climate tendency was-0.15/ years.The annual number of TPSL has two change cycles,the quasi 3 year cycle change and the quasi 12 year cycle change.In the summer half year,TPSL accounts for 81.7%,and TPSL accounts for 18.3% of the total in the winter half year.In the high frequency year,the subtropical high and the South Branch slot is stronger than low frequency year,and in high frequency year of TPSL,the plateau is a convergent flow field;the plateau is a divergent flow field in low frequency year.