摘要
为加深了解强对流的机制和特点,弥补雷达探测能力的不足,针对一次由3条阵风锋共同触发强对流过程,利用业务中尺度模式WRF进行了数值模拟,通过经本地化改进的指数探索触发关键因素,并与雷达探测资料对比分析。结果表明:(1)本地业务模式对此次过程天气背景与关键系统具有一定的模拟效果,但把握对流单体的能力十分有限,需辅以其他参数方可揭示新生雷暴触发机制。(2)本地化改进Micro Burst Index(MBI)与Turbulent Kinetic Energy(TKE)相互印证,体现了对流与阵风锋的重要特征。MBI高值区的范围、强度与原生对流特征相符,外缘与阵风锋位置吻合,强内核面积与各阵风锋强度一致,反映出各阵风锋及其触发能力存在差异。(3)3条阵风锋及MBI强度、850 hPa风场和下垫面特征的不同,决定了阵风锋各个交汇点是否触发新生对流,以及新生对流的强度与传播方式的不同。(4)强迫上升由3部分组成,其中阵风锋沿地形强迫上升贡献占垂直运动的1.1%,围拢挤压占40.9%,阵风锋的直接强迫最强占58.0%。上述共同作用导致强烈的上升运动,促使地表空气上升到海拔4300 m远超出LFC,并与局地水汽条件相配合,是触发异常强烈新生对流的关键。大气低层自东向西传播的重力波也有利于新生对流的触发。(5)MBI计算简单方便,可揭示模式难以直接反映的重要特征,经不断完善可望为无缝隙网格预报提供关键线索。
In order to further explore the mechanism of severe convection triggered by gust front in arid northwest China,overcome the radar’s incapability to detect gust front,operational numeric model mesoscale WRF is applied to simulate a severe secondary convection which propagated reversely and triggered by three gust fronts in Northwest China arid area.Locally modified index is used to investigate the key factors of triggering mechanisms and comparison analysis between simulations and radar sounding data is conducted.The results show that:(1)The mesoscale WRF model relatively well reproduces the atmospheric backgrounds,but shows a limited capability to describe the convective cells and the gust fronts directly,and it is necessary to develop specific index to reveal the mechanism of convection trigging according to local meteorological situation.(2)MBI and TKE show mutual corroboration and demonstrate the differences between the 3 gust fronts and their trigging characteristics.The areas and intensities of the modified MBI high value regions are consistent with the characteristics of original convections,the out-flow edges align with the positions of the 3 gust fronts,and the core high value areas accord with the intensities of gust fronts.(3)Comprehensive conditions of the areas and intensities of MBI relating to 3 gust fronts,wind field at 850hPa and vapor diversities of surface characteristics,leads to the capability differences of 3 colliding points which trigger secondary convections,and reveal their severities and propagation behaviors.(4)Gust fronts force causes strong updraft of 1.74 m·s-1,upraising the surface air over LFC.Orographic effect contributes 1.1%of uplift,enclosing press and directly force makes up 40.9%and 58.0%respectively.Extraordinary force and favorable vapor are keys to trigger this extreme violent secondary convection,while the gravity wave propagating east at low altitude of atmosphere is favorite to trigging.(5)The numeric simulation and MBI analysis suggest that this simple and practical index is able to depict gust front’s characteristics that are difficult for models to reflect directly.It can be expected to provide clues for seamless grid forecasting after further practice.
作者
胡文东
杨侃
文小航
张莹
HU Wendong;YANG Kan;WEN Xiaohang;ZHANG Ying(Key Laboratory of Plateau Atmosphere and Environment of Sichuan Province,Chengdu 610225,Sichuan,China;College of Atmospheric Sciences,Chengdu University of Information Technology,Chengdu 610225,Sichuan,China;Key Laboratory for Monitoring,Early Warning and Risk Management of Agrometeorological Disasters with Characteristics in Dry Areas,China Meteorological Administration,Yinchuan 750002,Ningxia,China;Ningxia Meteorological Office,Yinchuan 750002,Ningxia,China)
出处
《高原气象》
CSCD
北大核心
2021年第4期773-788,共16页
Plateau Meteorology
基金
国家重点研发计划专项(2018YFC1506104)
四川省科技厅项目(2018JY0056)
宁夏重点研发项目(2018BEG03002)
中国气象局预报员专项(CMAYBY2019-131)
成都信息工程大学启动项目(2016018)
干旱气象科学研究基金项目(IAM201810)
气象信息共享与数据挖掘四川省高校重点实验室项目(QGX18004)。
