Cause Analysis of a Torrential Rain Process in the Northeast Low Vortex
A continuous torrential rain occurred during 15-17 May 2013 in the lower reaches of the Yangtze River,and the error of predicted precipitation numerical model was significant.By using the conventional meteorological data,NCEP 0.5 ° × 0.5°grid data and Doppler radar images to analyze this process,it is indicated that the synoptic scale background was southwest airflow,low-vortex shear and thick wet layers.The torrential rain in the northeast of low vortex was related closely to disturbance and curvature of lower easterly jet.Convergence line on the ground layer triggered the upward movement.The torrential rain areas had good relationship with the superposition of wind shear line at level 700 hPa and surface mesoscale convergence line,and also related closely to negative divergence center of moisture flux at level 925 hPa.The velocity product of Doppler radar indicated obviously convergence,velocity area ratio of positive to negative reached to 1 ∶ 3.The radar echoes continuously generated,the "train effect" emerged at the downstream area.During the heavy rain period,echoes intensity was between 30 to 40 dBz,and precipitation per hour was between 16 to 20 mm.Numerical model tests showed that the easterly jet intensity and cyclonic curvature were underestimated at mid and low-atmospheric layer,which resulted in the heavy rain.The position and intensity deviation of ground convergence line resulted in deviation of rainfall center position.Predicted results could be corrected by analyzing real observation and radar data.
torrential raineasterly jetmoisture flux divergenceradar echo characteristicmodel test
NETL
NSTL
万方数据
维普
