| 贺兰山东麓极端暴雨的中尺度特征 |
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| 引用本文： | 陈豫英,苏洋,杨银,张肃诏,杨婧.贺兰山东麓极端暴雨的中尺度特征[J].高原气象,2021(1):47-60. |
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| 作者姓名： | 陈豫英 苏洋 杨银 张肃诏 杨婧 |
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| 作者单位： | 中国气象局旱区特色农业气象灾害监测预警与风险管理重点实验室;宁夏气象防灾减灾重点实验室;宁夏气象台 |
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| 基金项目： | 国家自然科学基金项目(41965001);中国气象局预报员专项(CMAYBY2019-130,CMAYBY2018-084)。 |
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| 摘 要： | 利用近10年宁夏逐时自动气象站降水、银川CD雷达、FY-2、探空和ECMWF再分析0.125°×0.125°等高分辨率多源气象资料,在中尺度系统分型基础上,对比分析贺兰山东麓6次极端暴雨的中尺度特征。结果表明:(1)低空偏(东)南急流夜间增强并配合贺兰山地形,在东坡山前触发或增强了暴雨中小尺度系统,造成地形处降水增幅,极端暴雨都是伴有短时强降水的对流性暴雨,主要集中在东坡山前,中心在山洪沟口,夜雨特征显著。(2)环境场都满足对流性暴雨的3个基本条件:700 hPa(东)南急流将暖湿水汽输向暴雨区,低层高温高湿促进了大气不稳定与动力、热力、地形抬升触发机制;深对流过程850 hPa无明显急流,水汽主要来自孟加拉湾,水汽输送受限,但大气稳定度更低,更有利于对流性暴雨发生,混合对流过程850 hPa与700 hPa急流路径重合,水汽来自孟加拉湾、南海、黄海和渤海,水汽输送更充沛,更有利于持续性暴雨产生。(3)极端暴雨主要有暖区对流降水、锋面对流降水、锋区层状云降水3种性质;暖区对流主要在山区,地形抬升是触发机制,锋面对流的触发是低层暖湿气流沿着冷垫抬(爬)升,平原和山区皆有;对流系统的移动与低层风场一致,山区和平原分别沿山体和低空急流轴传播,通常移动与传播方向平行,山区低层为偏东风时,移动与传播近似垂直,列车效应明显。(4)线型对流系统过程冷空气弱,以暖区或(和)锋面对流性降水为主,对流系统在山前沿山体传播形成组织化程度高的带状线型回波,移动与传播有平行有垂直,受地形抬升作用,对流系统在山前稳定少动、发展强盛,降水历时短、范围小、雨强大、有间歇性,3~4 h的累计雨量占过程总量的85%左右,区域平均雨量远小于暴雨量级,地形性强对流暴雨特征凸显。(5)非线型对流系统过程冷空气强,以锋面对流性降水和锋区层状云降水为主,对流系统在山前和平原沿山体和急流轴传播和移动形成非线型回波,平原地区传播与移动平行,山区两者垂直,对流系统组织化程度不高、移速快、强度弱,降水历时长、范围大、雨强小,连续降水累计雨量大,区域平均雨量接近或达到暴雨量级,混合性降水特征明显。(6)降水强度R与CAPE增幅、回波强度Z、强回波持续时间、回波顶高、液态水含量呈正相关,与TBB呈负相关,相关性在深对流过程更清晰;Z≥40 dBZ时,Z-R满足关系式:R=3.67×10-8Z5.222+4.835。
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| 关 键 词： | 极端暴雨 中尺度对流系统 低空急流 地形影响 列车效应 |
The Mesoscale Characteristics of Extreme Rainstorm in the Eastern Region of Helan Mountain |
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| CHEN Yuying,SU Yang,YANG Yin,ZHANG Suzhao,YANG Jing.The Mesoscale Characteristics of Extreme Rainstorm in the Eastern Region of Helan Mountain[J].Plateau Meteorology,2021(1):47-60. |
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| Authors: | CHEN Yuying SU Yang YANG Yin ZHANG Suzhao YANG Jing |
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| Institution: | (Key Laboratory for Meteorological Disaster Monitoring and Early Warning and Risk Management of Characteristic Agriculture in Arid Regions,CMA,Yinchuan 750002,Ningxia,China;Ningxia Key Laboratory of Meteorological Disaster Prevention and Mitigation,Yinchuan 750002,Ningxia,China;Ningxia Meteorological Observatory,Yinchuan 750002,Ningxia,China) |
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| Abstract: | Using high-resolution multi-source data such as the hourly precipitation of automatic weather stations in the past 10 years,Yinchuan CD radar,Temperature of Black Body of FY-2 satellite,radiosonde data and ECMWF reanalysis data(0. 125°×0. 125°),the mesoscale characteristics of six extreme rainstorms in the Eastern Region of Helan Mountain were analyzed based on the classification of mesoscale systems. The rainstorm dominated by linear convection system is deep convection,while the rainstorm dominated by nonlinear convection system is mixed convection. The results show that:(1)The low-level southeast jet enhances and triggers mesomicro scale rainstorm systems in the eastern slope of Helan Mountain at night,leading to the extreme rainstorms are convective rainstorms with short-time heavy rainfall. The rainstorm is mainly concentrated in the eastern slope of Helan Mountain especially centralizes in the mouth of shanhong ditch with remarkable characteristics of night rain.(2)All the extreme rainstorm environment fields meet the three basic conditions of convective rainstorm. Low-level southeast jet at 700 hPa transports warm and moist flow to heavy rainfall areas,which promotes the atmospheric static instability,dynamic,thermodynamic and topography lifting trigger mechanism.There is no obvious low-level jet at 850 hPa in the rainstorm dominated by deep convection system. Vapor source is the Bay of Bengal. Limited water vapor transport condition but lower atmospheric stability is more favorable to convective rainstorm. However,the path of low-level jet at 850 hPa coincides with low-level southeast jet at 700 hPa in the rainstorm dominated by mixed convection system. Moisture transport from the Bay of Bengal,the South China Sea,the Yellow Sea and the Bohai Sea are the source of the extreme rainstorm. The more moisture transport contributes to sustained rainstorm.(3)Extreme rainstorm is mainly divided into convective precipitation in the warm zone of front,frontal convective precipitation and stratiform precipitation of frontal zone. Convective precipitation in the warm zone of front mainly occurs in the mountain areas,and its trigger mechanism is topographic uplifting. Frontal convective is triggered by warm and moisture flow lifted on the cold surface,and it could occur in plains and mountains. The movement of convective system is consistent with lower wind field. It propagates along mountain in the mountain areas but along the low-level jet in plains. Usually the movement of convective system is parallel to the direction of propagation. However,when the lower level dominated by east wind in the mountain areas,it moves approximately perpendicular to the direction of propagation with obvious train effect.(4)There is a weak cold air in linear convective rainstorm,and the types of rainstorm are mainly convective precipitation in the warm zone of front and frontal convective precipitation. Convective system propagates along the mountain and form the linear zonal echo with high degree of organization,its movement could be parallel or perpendicular to the direction of propagation. It develops strongly and maintains a long time in front of the mountain affected by topographic uplift. So the rainstorm has features such as the short duration,the small range,the great rainfall intensity and the intermittent precipitation. Cumulative rainfall of 3~4 h of rainstorm accounted for about 85% of the total amount of the process,and the area mean rainfall is much smaller than heavy rain magnitude,which reflects the feature of topographic strong convective rainstorm.(5)Cold air is active in nonlinear convective precipitation. It is dominated by frontal convective precipitation and stratiform precipitation of frontal zone. Convective system propagates along the mountain in the mountain areas and along the jet stream axis in plains,forming the nonlinear echo. It moves parallel to the direction of propagation in plains while its movement could be parallel or perpendicular to the direction of propagation in the mountain areas. Convective system moves quickly with weak intensity and low degree of organization. Rainstorm has features such as the long duration,the large range,the small rainfall intensity,the continuous precipitation and the large cumulative rainfall. The area mean rainfall is close to or equal to the heavy rain magnitude. It has the remarkable characteristic of mixed precipitation.(6)The precipitation intensity is positively correlated with CAPE amplification,echo intensity,duration of strong echo,echo tops and vertically integrated liquid,but negatively correlated with TBB. Correlations are clearer in rainstorm dominated by linear deep convection. The positive correlation between precipitation intensity R and echo intensity Z is the most significant when the echo intensity is more than 40 dBZ(R=3. 67×10-8×Z5. 222+4. 835). |
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| Keywords: | Extreme rainstorm mesoscale convective system low-level jet topographic influence train effect |
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