GRAPES_MESO模式对一次强降水过程的预报及误差分析

本文应用西南低涡大气科学试验加密观测资料,常规探空与地面资料,自动站资料等,分析国家数值预报中心运行的GRAPES_MESO中尺度模式对2010年7月14～19日四川强降水过程预报能力.结果表明,模式降水预报能一定程度反映实况降水.在模式误差分析基础上,指出造成降水预报偏差的可能原因是模式预报的高度场持续偏低,预报低值系统偏强,高值系统偏弱,不利于四川上空的辐合低值系统维持；预报的登陆台风强度偏强,台风外围气流与副高外围环流结合,导致西南低空急流较强,加之,模式预报盆地水汽场在西部偏多,东部偏少,对流层中低层冷空气活动偏弱,暖湿气流活动较强,急流带北移较快,辐合流场位置偏北偏东,导致了积分后期预报降水与实况出现较大偏差,盆地东北部降水偏弱,预报降水落区偏东、偏北.探空分析还指出,盆地测站温度偏差较大,可能是受复杂地形条件下插值误差以及观测误差影响所致,由于盆地测站风向受周边地形影响较大,各站和各层分析风的不确定性较大.误差分析揭示了高度场预报偏低,温度场偏高,地面气压偏低等基本特征,误差的来源需要作进一步的数值试验与动力诊断分析.

Prediction and Error Analysis of a Heavy Rain Process with GRAPES_MESO Model

Using southwest vortxt experiment data,routine radiosonde and surface data,automatic meteorological observing station data and so on,the prediction performance has been analysed with Grapes_meso model run by National Numerical Prediction Center for a heavy rain process happening over Sichuan province from 14 to 19 July.2010.The results show that the precipitation prediction can reflect real precipitation on some certainty.Based on the model error analysis,the article points out the reasons leading to the error of precipitation prediction that may be the lasting lower height fields of prediction,the stronger low systems and the weaker high system,which made the convergence low system maintain over Sichuan.The stronger landing typhoon prediction,whose periphery air linked to the periphery air of subtropical high leaded to southwest low air prediction stronger.Additionally,vapor prediction was more in western and less in eastern over the basin,cold air intensity prediction was weaker,and warm and wet air were active,the jet band moved faster,so,the place of convergence field was more in northern and eastern,which leaded bigger precipitation error with the model integral time increasing,the rainfall was weaken in the northeast,the precipitation areas were more in northern and eastern.The radiodsonde analysis also indicated the temperature deviation in the basin was bigger,which maybe caused by interpolation error under complex terrain condition and observing error.Due to terrain effect on the stations in the basin,the wind analysis occurred greater uncertainty.The results also revealed the basic error characteristics,such as higher negative error possibility of height and surface pressure,positive error possibility of temperature and so on.The error origin will need to be analysed further by the means of numerical experiments or dynamics diagnose.