Analysis of Tibetan Plateau Vortex Activities Using ERA-Interim Data for the Period 1979-2013

Based on the ECMWF Interim reanalysis (ERA-Interim) 500-hPa height data for the period 1979-2013, the Tibetan Plateau vortex (TPV) activities are investigated with an objective identification and tracking algorithm. The vortex tracks over the Tibetan Plateau (TP) and its vicinity are identified, and the cold/warm nature of the TPV is revealed from the 500-hPa temperature fields. A TPV activity dataset is thus derived. Examination of the TPV frequency, intensity, persistence, geographical location, and migration from the TP suggests an average of 53 TPVs annually during the study period, with 6.7 of them shifting out of the TP. For these vortexes, the longer the lifetime, the lower the frequency, and 81% of the TPVs are initially warm in nature. The particularly high-intensity vortexes occur dominantly in the rainy period (May-September), with their origin mainly in western Nagqu and northern Ali. They disappear largely in the Tanggula maintain area on the east side of the vortex high-frequency center and the Dangqu River valley in western Qinghai Province, possibly due to the topography. It is also found that the frequency of TPVs is decreasing, with 2 fewer TPV occurrences per 10 yr. Meanwhile, it is statistically significant that 1.4 fewer TPVs move out of the TP and the percentage of TPVs moving out of the TP versus the total number of TPVs has reduced by 2.3% every 10 yr.