Diagnosis of a Torrential Rain Process in Liaoning Province

By using conventional observation data and NCEP 1°× 1°reanalysis grid data,the circulation background,role of low-level jet in storm rainfall,stability and dynamic conditions of the torrential rain occurred during July 19-20,2010 in Liaoning Province were analyzed.The results showed that:the divergence field at 200hpa,long-wave trough over 500hpa inducing cold air eastward to the storm zone and the stable maintenance of subtropical high constituted very favorable circulation background for the torrential rain.Apparent underlying moisture convergence in the upper level,middle-level moisture divergence occurring over the storm zone and the long-time maintenance of bottom moisture convergence provided favorable moisture conditions for the continuous heavy rain.Invasion of cold advection leads to the energy strength in the storm zone,so the cold advection loop was one of the generation and trigger mechanism of the heavy rainfall.The increasing upper divergent field benefited the enhancements and maintenance of low voltage and strengthened convective instability and vertical circulation over storm zone.