Analysis of Background and Physical Factors of Regional Torrential Rain in Ningxia on August 20-21,2018
[Purposes]By using the routine observation data,sounding data and NCEP/NCAR 1°×1°re-analysis data every 6 hours,the circulation background and physical factors of the regional rainstorm in Ningxia on August 20-21,2018 were analyzed to provide reference for local rainstorm forecast.[Meth-ods]Based on the circulation analysis and physical quantity diagnosis method,the circulation back-ground,influence factors,water vapor,thermal and dynamic factors of the heavy rainfall were analyzed.[Findings]The results showed that the precipitation process was produced under the background of"two grooves and two ridges"in Eurasia,in conjunction with the Low Vortex and shear line.700 hPa water va-por transportation was the main water vapor condition.36°～39°N Under 700 hPa was the strong conver-gence region,and the convergence center was inclined to the north,which was favorable for upward and downward suction and enhanced upward motion.In the horizontal direction,the convergence region and divergence region appeared in pairs,which was beneficial to the enhancement of horizontal convergence and divergence and the maintenance of ascending motion.The persistent existence of northwest-southeast high energy tongue provided sufficient unstable energy for strong convective weather.[Conclu-sions]The favorable circulation background,700 hPa sufficient water vapor,combined with certain dy-namic and thermal conditions caused the formation and development of the heavy rain weather.
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