| The total area of Shanxi Province is 156000 square kilometers,80.1%of the total area is mountains and hills. Meteorological disasters occurred frequently in this special geographical condition with perplexing valley and complex topography, heavy rain is one of the most important disaster weather. A regional heavy rain in Shanxi at 8-14 July 2013 caused by serious disaster such as landslideds, collapse, houses collapsed, crop damage etc..Conventional and unconventional meteorological data is used in this paper to further study the cause of Shanxi heavy rain weather process. The large scale circulation, mesoscale influence system configuration, infrared satellite images, radar echo characteristics were analyzed. Mesoscale numerical model WRF was used to simulate the process of rainstorm in two rainstorm day, relevant physical quantities are analyzed at the same time. The results show as follows:This rainstorm occurred in the circulation background of east high and west low. There are frequent fluctuations of the trough and ridge in mid-high latitudes, subtropical high is stable and less dynamic with 584 dagpm line swinging in the middle and lower reaches of the Yellow River.The characteristics of mesoscale systems mutual disposition in this strong precipitation is significant. The phase of strong precipitation is consistency with significant wet area in middle and lower layer of troposphere; the southwest airflow on the west of the subtropical high formed the southwest jet below 700hPa layer, strong precipitation is accompanied with the southwest jet and locating in the wind speed convergence at front of the southwest jet; heavy rain occurred between shear of 700hPa and 850 hPa.The cloud related to this continuous intensive precipitation actuated by warm moist air flow at the west of subtropical high and shear line at 700hPa、850hPa. The cloud band shows a northeast-southwest trend alonging the edge of subtropical high, and the variation of it’s intensity is consistent with strength and displacement of mid-low shear. This is a typical rainstorm process caused by maintain of middle and low cloud, TBB of the center cold cloud cover effecting of rainfall area is less than-40℃.The center of this rainstorm fall area is Changzhi. The moving direction and intensity of radar echo is consistent with satellite images of FY-2E. There are two continuous phase of strong radar echo respectively from 04:00 at 9 July to 14:00 at 10 July and from 01:00 at 12 July to 04:00 at 13 July, the corresponding radar echo is mainly proformming stratiform echo and mixed precipitation echo, and the strongest radar echo is 40-63 dbz. Radar echo intensity and rainfall instensity are loosely related.The simulation results show that the rainstorm area is close to the facts, but there is a slight gap in rainfall. The physical quantities such as water vapor flux, water vapor flux divergence, vertical velocity, divergence, vorticity, convective available potential energy(CAPE), K index are analyzed.The simulation results of WRF model has a good reference value, but the accuracy and reliability need more improvement. The two regional rainstorm precipitation near the vapor flux value of the area and the water vapor convergence center, a large number of low-level moisture from the southwest transport to Shanxi, sufficient water vapor is a necessary condition of rainstorm. When heavy rainfall are strong vertical upward movement, the lower level positive vorticity negative vorticity, low-level convergence divergence vertical structures rise significantly, or whole layers of strong convergence, air and strong growth momentum, water vapor the uplift is very obvious. During heavy rain in the lower atmosphere has been in a precarious state, and the corresponding area also has a large CAPE values. Unstable convection continued to promote the development of the low-level moisture upward lifting play a crucial role, and a large convective available potential energy for storm occurs provide a sufficient condition. |
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