秦岭北麓盛夏典型突发性降水过程中低层风特征  

Characteristics of low-level wind during typical sudden precipitation processes at the northern foot of Qinling Mountains in midsummer

作　　者：刘嘉慧敏 李明[1,2] 欧阳雨 吉庆 王青霞 李文耀 李涵钰 LIU Jiahuimin;LI Ming;OUYANG Yu;JI Qing;WANG Qingxia;LI Wenyao;LI Hanyu(Shaanxi Meteorological Observatory,Xi’an 710014,China;Key Laboratory of Eco-Environment and Meteorology for the Qinling Mountains and Loess Plateau,Xi’an 710016,China;Hunan Meteorological Observatory,Changsha 410118,China;Baoji Meteorological Bureau of Shaanxi Province,Baoji 721006,Shaanxi,China)

机构地区：[1]陕西省气象台,陕西西安710014 [2]秦岭和黄土高原生态环境气象重点实验室,陕西西安710016 [3]湖南省气象台,湖南长沙410118 [4]陕西省宝鸡市气象局,陕西宝鸡721006

出　　处：《干旱气象》2025年第1期41-53,共13页Journal of Arid Meteorology

基　　金：中国气象局复盘总结专项(FPZJ2024-131),中国气象局创新发展专项(CXFZ2025Q020);中国气象局气象能力提升联合研究专项重点项目(24NLTSZ003)共同资助;秦岭和黄土高原生态环境气象重点实验室重点课题项目(2023K-2)。

摘　　要：低层风场变化对突发性降水的形成有重要作用,其通过改变低层大气的流场结构,进而影响低层大气的稳定性及垂直运动,促使对流云发生发展。基于长安站风廓线雷达资料、地面加密观测资料、欧洲中期天气预报中心发布的第五代大气再分析资料及多普勒雷达资料,分析盛夏(7—8月)副热带高压控制下秦岭北麓3次典型突发性降水过程[2023年8月6日11:00—12:00(简称“过程Ⅰ”)、2023年7月13日00:00—01:00(简称“过程Ⅱ”)和2022年8月3日18:00—19:00(简称“过程Ⅲ”)]中低层风场的演变特征。结果表明:3次过程均发生在副热带高压配合低层冷空气侵入的环流背景下,突发性强。过程Ⅰ和过程Ⅱ低层为偏西风冷空气侵入,过程Ⅲ为偏东风冷空气侵入。降水发生前长安地区大气呈显著不稳定状态,对流层中层垂直风切变较弱,这是3次降水过程局地性强的主要原因。盛夏长安站低层风速多年平均总体呈单峰型变化,风速随高度先增加再减小,1 000 m高度以下平均风速不超过3.14 m·s^(-1),小时风速存在明显日变化特征。低层风向随高度增加呈逆时针旋转,由西南风逐渐转为东南风。3次突发性降水过程发生前4~6 h,长安站低层大气存在冷空气侵入过程,且风速较多年平均明显加大。伴随低层冷空气的持续侵入,地面气温迅速下降,气压上升,对流触发,强降水产生。低层冷空气的持续侵入一方面在低层产生强烈的中尺度锋生,为突发性降水提供能量条件和触发条件;另一方面受秦岭北麓及关中盆地局地地形的阻挡作用,迫使低层冷空气强迫抬升,有利于降水增幅。The changes of low-level wind field play an important role in the formation of sudden precipitation,which can change the flow field structure in the lower atmosphere,thereby affect the stability and vertical movement of the lower atmosphere and promote the development of convective clouds.Based on wind profile radar data at Chang’an Station,observation data,the fifth generation atmo⁃spheric reanalysis data released by the European Center for Medium Range Weather Forecasting,and Doppler radar data,this study analyzed the evolution characteristics of the low-level wind field during three typical sudden precipitation events under the control of the subtropical high at the northern foothills of the Qinling Mountains in midsummer.These events occurred on August 6,2023,from 11:00 to 12:00(referred to as“Process Ⅰ”),July 13,2023,from 00:00 to 01:00(referred to as“Process Ⅱ”),and August 3,2022,from 18:00 to 19:00(referred to as“Process Ⅲ”).The results show that all three events occurred under the circulation background of the subtropical high combined with the intrusion of cold air at low level,exhibiting strong suddenness.For Process Ⅰ and Process Ⅱ,the in⁃trusion of cold air at low level was characterized by westerly winds,while for Process Ⅲ,it was characterized by easterly winds.Before the precipitation,the atmosphere over the Chang’an region was in a significantly unstable state,with weak vertical wind shear in the middle troposphere,which was the main reason for the highly localized nature of these three precipitation events.In midsummer,the multi-year average low-level wind speed at Chang’an Station generally exhibited a single-peak pattern,the wind speed initially in⁃creased with height and then decreased.The average wind speed below an altitude of 1000 meters did not exceed 3.14 m·s^(-1),and the hourly wind speed shows distinct diurnal variation characteristics.The low-level wind direction displayed a counterclockwise rotation with increasing height,shifting gradually from so

关 键 词：秦岭北麓 盛夏 突发性降水 低层风场 冷空气侵入 

分 类 号：P468.026[天文地球—大气科学及气象学]