高低层多尺度系统耦合作用下一次祁连山降水的数值模拟及诊断  

Numerical Simulation and Diagnosis of a Precipitation in Qilian Mountains under the Coupling of Upper and Lower Systems

作　　者：蒋强 魏林波[1] 李超[2] 李艳[1] 王泓宇 JIANG Qiang;WEI LinBo;LI Chao;LI Yan;WANG HongYu(School of Atmospheric Sciences,Lanzhou University,Lanzhou 730000,Gansu,China;Hubei Key Laboratory of Rainstorm Monitoring and Early Warning,Wuhan Rainstorm Research Institute,China Meteorological Administration,Wuhan 430205,Hubei,China;Qijiang District Meteorological Bureau,Chongqing 401420,China)

机构地区：[1]兰州大学大气科学学院,甘肃兰州730000 [2]中国气象局武汉暴雨研究所暴雨监测预警湖北省重点实验室,湖北武汉430205 [3]重庆市綦江区气象局,重庆401420

出　　处：《高原气象》2023年第5期1298-1310,共13页Plateau Meteorology

基　　金：甘肃省自然科学基金项目(22JR5RA444);国家自然科学基金面上项目(42275045);第二次青藏高原综合科学考察研究项目(2019QZKK0104);西北区域人工影响天气能力建设研究试验项目(ZQC-R18208)。

摘　　要：基于ERA5再分析资料和国家气象信息中心的CLDAS陆面格点降水数据,对祁连山一次典型的系统性降水过程开展了系统性的WRF数值模拟和降水机制诊断研究。环流背景场的动力诊断结果表明,中尺度的高空槽影响系统和低层局地尺度的绕流和爬流的协同作用提供了重要的动力条件,其中高空槽的发展产生的槽前中尺度动力抬升作用决定了此次降水过程强降水带的分布,而低层绕流和爬流为局地强降水的出现提供了直接动力条件。进一步的水汽输送和收支诊断结果表明,此次降水的水汽源地主要来源于四川盆地,绕流会为迎风坡前的降水区输送丰沛的水汽,爬流则会促进水汽沿地形高度的逆梯度输送,并在降水中心附近辐合;在强降水发生阶段,水汽的垂直输送作用对水汽收支的贡献最大,水汽的辐合作用次之,水汽局地变化基本可以忽略。最后大气层结特征的诊断结果表明,当大气动力条件和水汽条件都有利于降水时,配合对流层中低层层结不稳定性的增强,更易触发对流,从而增强迎风坡前强降水。Based on ERA5 reanalysis data and CLDAS land grid precipitation data from the National Meteorological Information Center,a systematic WRF numerical simulation and precipitation mechanism diagnosis of a typical systematic precipitation process in the Qilian Mountains are carried out in this paper.The dynamic diagnosis results of the circulation background field show that the interaction between the mesoscale upper trough system and the local lower flow around and flow over provides important dynamic conditions.The mesoscale dynamic uplift in front of the trough caused by the development of the upper trough determines the distribution of the heavy precipitation belt during the precipitation process,while the lower flow around and flow over provide direct dynamic conditions for local heavy precipitation.The further diagnosis results of water vapor transport and budget show that the water vapor source of this precipitation mainly comes from the Sichuan Basin.The flow around will transport abundant water vapor for the precipitation area in front of the windward slope,and the flow over will promote the reverse gradient transport of water vapor along the terrain height and converge near the precipitation center.In the stage of heavy precipitation,the vertical transport of water vapor contributes the most to the water vapor budget,followed by the convergence of water vapor,and the local variation of water vapor can be basically ignored.Finally,the diagnostic results of atmospheric stratification characteristics show that when both atmospheric dynamic conditions and water vapor conditions are conducive to precipitation,combined with the enhancement of the instability of low and medium tropospheric stratification,it is easier to trigger convection and enhance precipitation in front of the windward slope.

关 键 词：祁连山降水 WRF数值模拟 不同尺度 形成机制 

分 类 号：P426[天文地球—大气科学及气象学]