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副高影响下陕西关中强对流发生的环境场特征及触发机制
赵 强1, 陈小婷2, 王 楠3, 彭 力4
(1.陕西省气象台,秦岭和黄土高原生态环境重点实验室灾害性天气研究与应用中心;2.陕西省气象台;3.陕西省气象台,西安;4.陕西省铜川市气象局)
The Environmental Characteristics and Trigger Mechanism of Severe Convection under the influence of Subtropical High in Shaanxi Guanzhong Area
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投稿时间:2020-12-04    修订日期:2021-06-10
中文摘要: 2015-2018年陕西关中出现了四次副热带高压(简称副高)影响下的强对流天气,造成局部地质灾害和城市内涝,全球模式对短时暴雨出现了漏报,本文利用ERA5再分析资料(0.25×0.25)、地面加密自动站和西安站多普勒天气雷达等资料,分析此类强对流的环境场特征和触发机制,为预报预警提供思路。分析结果表明:陕西关中副高控制下的强对流往往与高温天气并存。对流发生时低层水汽含量大,可降水量在50 mm以上;相对于副高外围的系统性暴雨,此类天气水汽输送较弱;水汽输送强弱决定了过程总雨量大小。此类强对流强辐合中心位于地面到800 hPa,相对于系统性暴雨辐合中心位置更低,低层的辐合主要作用是克服对流抑制,释放不稳定能量。对流发生有利的环境条件包括:强的位势不稳定层结、低自由对流高度、中等强度对流有效位能、较厚的暖云层。触发机制主要是地面冷锋和低层风场辐合线,上游冷锋后的降水降温效应,会加大温度梯度使冷锋增强,锋面侵入副高内部高温、高湿大气,触发对流;暖区对流一般由地面中尺度辐合线触发,对流产生的冷池前沿阵风锋触发新生对流。秦岭地形对对流的移动和传播有明显影响,在关中北部新生对流南移过程中容易在秦岭北麓沿山维持,造成暴雨天气。而在秦岭北麓的地形辐合线上新生的对流系统,下山过程中由于势能向动能转化,对流系统移速加快,其出流边界触发平原地区对流发展,强降水持续时间较短,更容易产生大范围雷暴大风天气。
中文关键词: 强对流  阵风锋  大气不稳定  触发机制  锋生  地形
Abstract:Using conventional observation data, doppler radar data of Xi’an station, ground weather station observation data and ERA5 reanalysis data (0.25*0.25), the environmental conditions and triggering mechanism of four severe convection weathers in Guanzhong area under the influence of subtropical high from 2015 to 2018 were comparative analyzed. These four cases resulting in local geological disasters and urban flooding, however, the global model failed to forecast a short-term rainstorm. Results show that the severe convection in Guanzhong area under the control of subtropical high often coexists with the hot weather. When severe convection occurs, low-level atmospheric water vapor content is large, the atmospheric precipitable water can be more than 50 mm, relative to the systemic rainstorm occurred in the peripheral of the subtropical high, the water vapor transmission is relatively weak, the strength of the water vapor transmission determines the total rainfall in the severe convection process. Convergence center is located on the ground to 800 hPa, compared with the systemic rainstorm, the convergence center position is lower, and the main role of low-level convergence is to overcome convection suppression, release unstable energy. Favorable environmental conditions for the occurrence of severe convection including strong potential unstable layer, low LFC, medium intensity convective available potential energy and thick warm clouds. The trigger mechanism is mainly cold front and low-level wind convergence line, when there is a cold front in the upstream, the cooling effect of precipitation behind the cold front will increase the temperature gradient to enhance the cold front, cold air in the lower layer invades the atmosphere with high temperature and high humidity controlled by subtropical high, triggering severe convection occurs; The convection in warm regions is usually triggered by ground convergence line, convection induced cold pools can form gust front and trigger new convection. Qinling terrain has a significant impact on the movement and spread of the severe convection. The convective that triggers in north of Guanzhong area and move southward can easily cause heavy rain storm because of the rain belt blocked by Qinling. The new convective occurred along the terrain convergence line in the northern Qinling triggers new convective development in Guanzhong area, as the potential energy is converted to kinetic energy during the descending process, the convection system moves faster and the duration of heavy precipitation is shorter, it is easier to produce large-scale thunderstorm and gale weather.
文章编号:202012040429     中图分类号:P458.2    文献标志码:
基金项目:2021年度中国气象局创新发展专项《“十四运”预报预警技术研究及应用》(CXFZ2021Z035)及《2020年灾害性天气预报技术总结分析》(CXFZ2021Z034);国家自然科学基金《基于稀疏对应和深度神经网络的雷达回波外推短临降水预报研究》(42075007);;中国气象局预报员专项(CMAYBY2020-129)秦岭和黄土高原生态环境气象重点实验室重点课题(2019Z-1,2020K-1)。
引用文本:
赵 强,陈小婷,王 楠,彭 力,0.The Environmental Characteristics and Trigger Mechanism of Severe Convection under the influence of Subtropical High in Shaanxi Guanzhong Area[J].Meteor Mon,():-.
ZHAO Qiang,CHEN Xiaoting,WANG Nan,PENG Li,0.The Environmental Characteristics and Trigger Mechanism of Severe Convection under the influence of Subtropical High in Shaanxi Guanzhong Area[J].Meteor Mon,():-.