Variation characteristics of Tibetan Plateau vortex during 1979-2016

Tibetan Plateau Vortex(TPV)is one of the major systems that induce heavy rain in China during summer. Based on ERA-Interim daily reanalysis data from 1979 to 2016, we have identified TPVs by using an objective identification method, and compared these TPVs to the TPVs in Tibetan vortex and shear line yearbook (here in after referred to as yearbook) in certain years. The main results are as follow. (1) The average agreement rate between TPVs by objective identification and ones from yearbook was 66.2%, and the frequency and the center geopotential height of both TPVs have a clear correlation. (2) During the past 40 years, the frequency of the TPVs has increased significantly. The annual mean TPV frequency was 56.3, which presents a quasi-six-year and a quasi-ten-year periodic oscillation. (3) The center geopotential height of the TPVs has a normal distribution, whose duration decreased exponentially, and the frequency, center height and duration all presented a pattern of strong or long in summer and weak or short in winter. (4) The high TPV frequency area was situated in 33°-36°N and 80°-90°E, whose axis is located around 35°N, with two high TPV frequency centers being in the eastern Nagqu and northern Ngari. The TPVs generated in the western, central and eastern areas accounted for 32.6%, 46.0% and 21.4% of total TPVs, respectively. The eastward-moving, quasi-stationary and westward-moving types of TPVs accounted for 61.4%, 34.3% and 4.3% of total TPVs, respectively. (5) The TPV dataset established based on the objective identifying method can provide important references for the further research of TPV.