2011•Journal of Meteorology and EnvironmentRequires access
Comparison of two rainstorm processes in Zhejiang province caused by northeast cold vortex
Lou Xiao-fen
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Abstract
Two rainstorm processes caused by northeast cold vortex occurred in the early June of 2009 in Zhenjiang province,and both had the different features.Based on the conventional meteorological data,data from automatic weather stations,the NECP reanalysis data and satellite images,the large-scale circumfluence background,dynamical and thermodynamic conditions,water vapor conditions of two processes were compared.The results indicate that weather situation is different because of the differences of temperature fields at middle and low levels and intensity of systems from upstream to downstream.The rainstorm on June 2nd is a continuously regional process and is mainly generated by stratiform cloud.The rain band distribution is zonal.There are large range convergence at low level and divergence at high level.The convergence at low level is stronger than the divergence at high level.The southwest jet steam exists at low level,which provides the important water vapor and dynamical conditions for rainstorm.Atmospheric stratification is stable.By comparison,the rainstorm on June 5th is a severe convection weather process.The distributions of precipitation are uneven,and precipitation intensity is strong and duration is short in this process.There are not large range convergence and divergence areas at high and low levels and southwest jet stream at low level.Water vapor conditions are poor in the early period of precipitation.This process is mainly generated by thermodynamic action,and unstably atmospheric stratification triggers the severe convection weather and results in the local rainstorm.The key points of forecasting are the structures of divergence at high level and convergence at low level as well as southwest jet stream at low level for the first regional rainstorm process,while those are atmospheric stratification instability degree and incursion of dry and cold air from the rear of northeast cold vortex for the second local rainstorm process.