关键词: 西南低涡, 高原涡, 强降水, 对流云团, VVP风场反演

Abstract:

Based on the conventional observation data, NCEP reanalysis data, satellite and Doppler radar data, a southwest vortex rainstorm process in Sichuan-Chongqing region from August 16 to 18 in 2015 was analyzed. The results indicate that the Tibetan Plateau vortices moving eastward and the cold air invading into Sichuan Basin contributed to the development of southwest vortex, and finally led to the heavy rainfall occurring under the relatively stable circulation background at middle-high latitude and low latitude in Asia. At the primary formation stage of southwest vortex, a cold front intruded on the northeast side of the surface thermal low pressure, a warm front formed on the north side of the center and the Southwest vortex was close to the positive pressure. At the stage of stable and sustainable development, the south part of the cold front moved to the south side of the low pressure, and the north part combined with the warm front to form a quasi-stationary front. The baroclinic property of the low vortex was obvious and nearly circular, and the continuous rainstorm mainly appeared near the warm shear line of the southwest vortex and the east side of the cold trough. At the weakening stage of southwest vortex moving eastward, the cold air invaded again, the cold front continued to strengthen, and the southwest vortex moving eastward deformed and weakened. The convergence at low-level, divergence at high-level, abundant water vapor transmission and accumulation of unstable energy played an important role in the deepening and development of southwest vortex and the maintenance of heavy precipitation. The convective clouds which developed near the warm shear line and the cold trough on the south side of low vortex led to the rainstorm. The heavy precipitation mainly occurred in the region with relatively large TBB gradient on the windward side of the cloud cluster. The local circulation of the heavy precipitation was composed of low level jet and shear lines or convergence lines. The wind vector of  wind inversion based on VVP (velocity volume processing) could more intuitively judge wind direction and speed, development stage of weather system, convergence line and shear line. The evolution of low-altitude convergence line, shear line and the intensity and direction of low level jet had important guiding significance for the dynamic conditions, maintenance time and echo extrapolation prediction of heavy rainfall weather.

Key words: southwest vortex, the Tibet Plateau vortices, heavy precipitation, convective clouds;  , wind inversion based on VVP（velocity volume processing）method