Impact Of Changes In The Intensity Of Weather Systems On Fine Time Precipitation Forecast

Based on FNL(Final Openrational Analysis) data, numerical simulations andtests are made with WRF model on two heavy rainfall processes(one happened inQingdao on BST5July to BST6July,2012and the other one which is a cycloneprocess caused storm surge happened in Qingdao on BST26to BST27May,2013).The study shows that the temperature advection and the heating by latentheat have an significant effect on the intensity and location of weather system inmodels.If the effect can be considered in the interpretation of numerical forecastproducts, the accuracy of timing in meticulous forcast will be improved.The amplitude of the upper trough is strengthened by heating of latentheat,which strengthen the intensity of the surface system.The heavy rain will bemaintained and develop by the positive feedback of latent heat.The all factor controltest and the dry sensitive test are made to study the cyclone process cased storm surgeon the coast of Qingdao BST26to BST27May2013.when the non-adiabatic heatingincrease by the height,the upper trough at500hPa will develop.At the same time,thedevelopment of surface system cause the low-level wind speed increase.So the stormsurge caused by southeast wind made the part of Zhanqiao collapse.The sensitivity to temperature advection of WRF model makes an effect on thelocation and the speed of the surface system.The simulation result of the surface theheavy rain on BST5July to BST6July,2012and the storm on BST26to BST27May,2013is northerly than the actual surface system.The numerical tests show thatthe difference is that the WRF model is sensitive to the temperature advection. Thesensitivity to temperature advection of WRF model is stronger than the actual,so theamplitude of the upper trough by simulation is strengthened.For this reason,thecomponent of the airflow on the front of the upper trough on the warp directionincrease,which cause the location of the surface system is northerly than theactual.Because the warp direction moving component of the surface system incease,the region of the rainfall diverge,the moving speed of the surface system iseffected,and the starting and end time of the rainfall is effected too.The study shows that the effect of the forecast of different numerical modelsrelates to the specific weather system.In the practice of the weather forcast,theanalysis and the decision of the forecast should be made by the characteristic of thedifferent models’ result in the different circulation feature. The judgement cant’t bemade by the general statistics of the accuracy rate of the forecast in the fineforecast,which require the forecaster to make the right decision to the change of theweather system and correct the result of the forecast reasonably based on grasping thefeature of the different numerical models.