meso-SAS对流参数化方案的改进及其在9km分辨率模式中的应用  

IMPROVEMENT OF MESO-SAS CUMULUS PARAMETERIZATION SCHEME AND ITS APPLICATION IN A MODEL OF 9 KM RESOLUTION

作　　者：徐道生[1] 张艳霞[1] 王刚 蒙伟光[1] 陈子通[1] 

机构地区：[1]中国气象局广州热带海洋气象研究所/广东省区域数值天气预报重点实验室,广东广州510080 [2]广州市海珠区气象局,广东广州510080

出　　处：《热带气象学报》2015年第5期608-618,共11页Journal of Tropical Meteorology

基　　金：公益性(气象)行业专项(GYHY201406003;GYHY201406009);自然科学基金项目(41275053;41505084;41505039);对流尺度集合预报技术与业务应用(2013A04);广东省气象局科学技术研究项目(2014B02)共同资助

摘　　要：在分辨率为9 km的华南中尺度模式中引进meso-SAS方案,结合一次季风槽内的华南暖区暴雨天气过程,对原meso-SAS方案中存在的一些问题进行了分析和改进。利用高分辨率模式对积云覆盖比进行诊断,结果表明在9 km网格中积云覆盖比已经不能再忽略不计,因此meso-SAS要比SAS方案更加适用于该模式。原meso-SAS方案中估算的积云覆盖比大致合理,但是分布很不连续,容易导致计算不稳定,通过格点平均垂直速度估算积云覆盖比可以避免出现这个问题。对于受大尺度强迫场影响不是很明显的局地性强降水过程,原meso-SAS方案中使用的"准平衡"闭合假设会引起比较大的降水预报偏差,使用不稳定能量的松弛调整进行闭合可以有效地改善降水预报效果。A meso-SAS cumulus parameterization scheme was applied into a mesoscale model for south China for the prediction of rainstorms happening in the warm section of monsoon troughs, and some of the drawbacks of this scheme were studied. As cumulus fractional area cannot be ignored in the 9 km model in the diagnosis of cloud resolving simulation, the meso-SAS scheme was more reasonable for this model than the original SAS scheme. The estimated cumulus fractional area in the meso-SAS scheme was reasonable though it was discontinuous, leading to computational instability. This problem can be avoided by using a grid-scale vertical velocity to estimate the cumulus fraction. The quasi-equilibrium assumption which was still used in the original meso-SAS scheme will cause obvious deviation in forecasting precipitation near the coastline. Through relaxed adjustment of instability energy in calculation of mass flux at the cloud base, the 48 h forecast of precipitation was substantially improved.

关 键 词：meso-SAS 积云覆盖比 对流参数化 闭合假设 降水预报 

分 类 号：P435[天文地球—大气科学及气象学]