Mesoscale analysis on the "6.16" heavy precipitation event in the west of Xinjiang

Based on conventional observational data, TBB data from FY-2G satellite, Doppler weather radar data, CMORPH satellite precipitation fusion data and NCEP/NCAR reanalysis data with 0.25°×0.25° spatial resolution, a rare torrential rainstorm event occurred in the west of Xinjiang from 16 to 17 June 2016 was studied. The results are as follows. (1) The heavy rain event had the features of large accumulated rainfall, strong storm intensity, local rainfall breaking record of daily precipitation, as well as broad distribution of short-time heavy precipitation. Rainstorm area was located in the left side of the export area of southwest jet at 200 hPa, nearby the southerly jet at 500 hPa and the convergence line on 700 hPa. Large values of CAPE and K indices had good instructional significance for the torrential rain. (2) The torrential rain event occurred in the favorable environment of convergence at low-level, divergence at high-level, and sufficient water vapor at low-level. Strong positive vorticity, convergence and ascent movement have continuously transported water vapor and energy upwards, providing very favorable environmental conditions for the generation of heavy rain. (3) In the process of development and evolution of mesoscale rain masses in Central Asia, a southwest-northeast multi-center rain belt was gradually formed, and the center successively arrived in the northern mountainous region of the Ili area, cooperating with the original mesoscale rain masses and resulting in heavy rain weather. The mesoscale convective cloud clusters were continuously generated in Central Asia, which continuously developed and strengthened in the process of eastward migration and arrived at the torrential rain zone in turn, which caused the continuous generation of short-term heavy precipitation in storm regions. (4) There were obvious differences in the mesoscale convective systems between the two periods of heavy rain, and the first time period was mainly isolated mesoscale convective systems. The direct system responsible for the emergence of storm centers and the strongest short-time heavy precipitation at the Borboson station in Yining was a mesoscale-γ convection monomer with obvious wind characteristics and maintenance of little activity in the rainstorm area. The second time period was a linear mesoscale convective system with CR 50 dBz, DVIL 4 g·m^-3, length of 70 km, and width of 10 km, which caused multiple stations short-time heavy rainfall weather in the process of moving eastward.