不同积云对流参数化方案对拉萨强降水过程的模拟

Study on the Simulation of Heavy Precipitation Processes in Lhasa with Different Parameterized Schemes of Cumulus Convection

利用NCEP 1°×1°再分析资料,使用WRFV 4.0中的7种积云对流参数化方案对2019年7月18日至19日拉萨市一次强降水过程进行数值模拟试验。结果表明:WRF模式能够较好地模拟本次高原低涡切变线的强降水过程,K-F、New-Tiedtke和N-SAS方案模拟的南部强降水区域,与实况较符合,但强度偏小,其中,K-F方案最接近实况。将模拟结果与GPM卫星降水资料进行对比发现,两者在北部强降水中心较为吻合。不同方案模拟的小时、累积降水量强度均偏小,强降水出现时间与实况比较一致。模式对小雨的模拟效果最好,各方案的TS评分均超过0.55,其中New-Tiedtke得分最高,为0.88;对中雨及以上量级预报能力不足。在主要降水区,θse和垂直速度剖面模拟结果显示,除BMJ、N-SAS方案以外,其余方案模拟的θse场呈现斜率大、上干下湿型,对本次强降水有一定的指示意义;但垂直速度基本为正值,是导致模式降水预报量级偏弱的原因之一。

A heavy precipitation process in Lhasa on18th and 19th of July in 2019 was simulated using reanaly-sis data of NCEP 1°×1°together with seven cumulus convective parameterized schemes in WRFV 4.0.The re-sults show that the WRF model can be use to simulate heavy precipitation process of the Plateau Vortex Shear Line quite well.In detail,the heavy precipitation in shouthern area simulated by the K-F,New-Tiedtke,and N-SAS schemes is more consistent with the observed one,but with smaller value in intensity.And among the three schemes,the precipitaiton simulated by the K-F scheme is the closest to the observed one.Comparing the simu-lated precipitation results with GPM satellite data,it is found that the northern heavy precipitation center and the occurrence time of the heavy precipitation are consisitent,and the hourly and cumulative precipitation intensity given by different schemes are smallin value.Regarding the simultion of light rain,these models performed very well with the value of TS higher than 0.55,among them the highest value given by New-Tiedtke scheme with the value of 0.88.However,the forecasting ability of moderate rain and above was insufficient.In the main precipita-tion area,the simulation results ofθse and vertical velocity profiles showed that except for the BMJ and N-SAS schemes,theθse field simulated by the others showed a large slope with dry in upper layer and wet in lower layer type,which had certain indicative significance for this heavy precipitation.However,the vertical velocity is posi-tive,which is one of the reasons for the weak magnitude of the precipitation forecast models.