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Initiation and Evolution of Long-Lived Eastward-Propagating mesoscale convective systems over the Second-Step Terrain along Yangtze-Huaihe River Valley

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Advances in Atmospheric Sciences 2022年第5期39卷 763-781页

作者： Yuanchun ZHANG Jianhua SUN Ruyi YANG Ruoyun MA Key Laboratory of Cloud-Precipitation Physics and Severe Storms(LACS) Institute of Atmospheric PhysicsChinese Academy of SciencesBeijing 100029China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai 519080China University of the Chinese Academy of Sciences Beijing 100049China Public Meteorological Service Center China Meteorological AdministrationBeijing 100044China

Based on the previous statistical analysis of mesoscale convective systems(MCSs)over the second-step terrain along Yangtze-Huaihe River Valley,eight representative long-lived eastward-propagating MCSs are selected for model-based sensitivity testing to investigate the initiation and evolution of these types of MCSs as well as their impact on downstream *** subject each MCS to a semi-idealized(CNTL)simulation and a sensitivity(NOLH)simulation that neglects condensational heating in the formation *** CNTL experiment reveals convection forms in the region downstream of a shortwave trough typified by persistent southwesterly winds in the low-to *** merging with other convective systems,moist convection develops into an MCS,which propagates eastward under the influence of mid-tropospheric westerlies,and moves out of the second-step *** MCS then merges with pre-existing local convection over the plains;the merged convection reinforces the cyclonic wind perturbation into a mesoscale vortex at 850 *** this vortex moves eastward to regions with local vortex at 850 hPa,another vortex at 925 hPa is also ***,the vortices at 850 and 925 hPa merge together and develop into a mesoscale convective vortex(MCV).In contrast,MCSs fail to form and move eastward in the NOLH *** the absence of eastward-propagating MCSs,moist convection and mesoscale vortices still appear in the plains,but the vortex strength and precipitation intensity are significantly *** is suggested the eastward-propagating MCSs over the second-step terrain significantly impact the development and enhancement of moist convection and vortices in the downstream areas.

关键词： mesoscale convective systems second-step terrain mesoscale convective vortex numerical sensitivity simulation

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ANALYSIS OF mesoscale convective systems OVER TIBETAN PLATEAU IN SUMMER

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Chinese Geographical Science 2006年第2期16卷 116-121页

作者： GUO Zhong-yang DAI Xiao-yan WU Jian-ping LIN Hui Key Laboratory of Geographic Information Science of Ministry of Education East China Normal University Shanghai 200062 P. R. China Department of Geography and Resource Management ＆ Joint Laboratory for Geolnformation Science the Chinese University of Hong Kong Hong Kong P. R. China

In this paper, Geostationary Meteorological Satellite (GMS) infrared black-body temperature (Tbb) data from June to August 1998 are used to automatically track the activity of mesoscale convective System (MCS) over the Tibetan Plateau in China. Consequently, the features of MCS, such as area, intensity, life cycle, activity region and shape, are obtained. High Resolution Limited Area Analysis and Forecasting System (HLAFS) values provided by China National Meteorological Center are used to study the relationships between the MCS trajectories and their environmental physical field values, based on the distribution and trajectories of MCSs over the Tibetan Plateau. Favorable environmental physical field charts of influencing MCS movement out of the Tibetan Plateau in different UTC (Universal Time Coordinate) are developed by using spatial data mining techniques at levels of 400hPa and 500hPa, respectively.

关键词： Tibetan Plateau mesoscale convective systems black-body temperature automatically tracking

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MAGE ANALYSIS OF GEOSTATIONARY METEOROLOGICAL SATELLITE FOR MONITORING MOVEMENT OF mesoscale convective systems OVER TIBETAN PLATEAU

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Chinese Geographical Science 2005年第3期15卷 231-237页

作者： DAI Xiao-yan WU Jian-ping LIN Hui Ministry of Education Key Laboratory of Geographic lnJbrmation Science East China Normal UniversityShanghai 200062 P. R. China Department of Geography and Resource Management ＆ Joint Laboratory for Geolnformation Science the Chinese University of Hong Kong Hong Kong P. R. China

Disaster weather forecasting is becoming increasingly important. In this paper, the trajectories of mesoscale convective systems （MCSs） were automatically tracked over the Chinese Tibetan Plateau using Geostationary Meteorological Satellite （GMS） brightness temperature （Tbb） from June to August 1998, and the MCSs are classified according to their movement direction. Based on these, spatial data mining methods are used to study the relationships between MCSs trajectories and their environmental physical field values. Results indicate that at 400hPa level, the trajectories of MCSs moving across the 105°E boundary are less influenced by water vapor flux divergence, vertical wind velocity, reIative humidity and K index. In addition, if the gravity central longitude locations of MCSs are between 104°E and 105°E, then geopotential height and wind divergence are two main factors in movement causation. On the other hand, at 500hPa level, the trajectories of MCSs in a north-east direction are mainly influenced by K index and water vapor flux divergence when their central locations are less than 104°E. However, the MCSs moving in an east and south-east direction are influenced by a few correlation factors at this level.

关键词： Tibetan Plateau mesoscale convective systems automatically tracking spatial data mining

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OBSERVATION AND MODEL ANALYSES OF POSITIVE CLOUD-TO-GROUND LIGHTNING IN mesoscale convective systems

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Acta meteorologica Sinica 1992年第4期6卷 501-510页

作者： Yan Muhong Guo Changming Qie Xiushu Ge Zhengmo Zhang Guangshu Lanzhou Institute of Plateau Atmospheric Physics,Academia Sinica,Lanzhou 730000

The analyses of spatial and temporal characteristics of positive cloud-to-ground(CG)lightning for four mesoscale convective systems and two severe local convective systems in 1989 and 1990 show that positive CG flash rate usually has two peak *** major peak occurs during the developing stage of the storm and most of the positive CG flashes originate at the lower part of the *** minor occurs during the dissipative stage of the storm and most of the positive CG flashes originate at the upper part of the storm,especially in the region of the wind divergence in the storm *** positive CG flash rate is almost an order of magnitude larger in the developing stage than in the dissipative *** appearing time of the peak of negative CG flash rate is in accordance with that of the valley of pos- itive CG flash rate. The higher the intensity of the radar echo,the higher the positive CG flash *** of the positive CG flashes oc- cur when the weak echo area is larger,and mostly originate in the region where the radar echo intensity is about 10dBz and in the back region of the moving *** spatial distribution of the positive CG flashes is much more dispersive than that of the *** mesoscale analysis reveals a bipolar lightning *** mean bipole--length reaches its minimum during the mature stage of the storm and reaches the maximum during the developing stage of the storm. The vertical distribution of the charge density is calculated by a one-dimensional charging ***,we discuss the producing condition of the positive CG lightning and forming cause of charge structure mentioned above.

关键词： mesoscale convective systems thunderstorm lightning electrification

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Improving the Analyses and Forecasts of a Tropical Squall Line Using Upper Tropospheric Infrared Satellite Observations

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Advances in Atmospheric Sciences 2022年第5期39卷 733-746页

作者： Man-Yau CHAN Xingchao CHEN Department of Meteorology and Atmospheric Science and Center for Advanced Data Assimilation and Predictability TechniquesThe Pennsylvania State UniversityUniversity ParkPennsylvaniaPA 16802USA

The advent of modern geostationary satellite infrared radiance observations has noticeably improved numerical weather forecasts and ***,compared to midlatitude weather systems and tropical cyclones,research into using infrared radiance observations for numerically predicting and analyzing tropical mesoscale convective systems remain mostly *** tropical mesoscale convective systems play a crucial role in regional and global weather,this deficit should be *** study is the first of its kind to examine the potential impacts of assimilating all-sky upper tropospheric infrared radiance observations on the prediction of a tropical squall *** though these all-sky infrared radiance observations are not directly affected by lower-tropospheric winds,the high-frequency assimilation of these all-sky infrared radiance observations improved the analyses of the tropical squall line’s outflow *** from that,the assimilation of all-sky infrared radiance observations improved the analyses and prediction of the squall line’s cloud ***,reducing the frequency of assimilating these all-sky infrared radiance observations weakened these improvements to the analyzed outflow position,as well as the analyses and predictions of cloud fields.

关键词： data assimilation infrared satellite observations numerical weather prediction mesoscale convective systems tropical meteorology

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STATISTIC CHARACTERISTICS OF MCSS OVER ASIA AND WESTERN PACIFIC REGION

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Journal of Tropical Meteorology 2012年第4期18卷 457-472页

作者：束宇潘益农王微 School of Atmospheric Sciences and Key Laboratory for mesoscale of Severe Weather/Ministry of Education Nanjing University Nanjing Meteorology Bureau

mesoscale convective systems (MCSs) are severe disaster-producing weather systems. Previous attempts of MCS census are made by examining infrared satellite imageries artificially, with subjectivity involved in the process unavoidably. This method is also inefficient and time-consuming. The disadvantages make it impossible to do MCS census over Asia and western Pacific region (AWPR) with an extended span of time, which is not favorable for gaining a deeper insight into these systems. In this paper, a fire-new automatic MCS identification (AMI) method is used to capture four categories of MCSs with different sizes and shapes from numerical satellite infrared data. 47,468 MCSs are identified over Asia and western Pacific region during the warm season (May to October) from 1995 to 2008. Based on this database, MCS characteristics such as shape, size, duration, velocity, geographical distribution, intermonthly variation, and lifecycle are studied. Results indicate that the number of linear MCSs is 2.5 times that of circular MCSs. The former is of a larger size while the latter is of a longer duration. The 500 hPa steering flow plays an important role in the MCS movement. MCSs tend to move faster after they reach the maximum extent. Four categories of MCS have similar characteristics of geographical distribution and intermonthly variation. Basically, MCSs are zonally distributed, with three zones weakening from south to north. The intermonthly variation of MCSs is related to the seasonal adjustment of the large-scale circulation. As to the MCSs over China, they have different lifecycle characteristics over different areas. MCSs over plateaus and hill areas, with only one peak in their lifecycle curves, tend to form in the afternoon, mature at nightfall, and dissipate at night. On the other hand, MCSs over plains, which have several peaks in their lifecycle curves, may form either in the afternoon or at night, whereas MCSs over the oceans tend to form at midnight. Affected

关键词： mesoscale convective systems automatic MCS identification (AMI) method velocity geographicaldistribution intermonthly variation lifecycle

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Numerical Simulation of Torrential Rainfall and Vortical Hot Towers in a Midlatitude mesoscale convective System

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Atmospheric and Oceanic Science Letters 2009年第4期2卷 189-193页

作者： ZHANG Man Da-Lin ZHANG WANG Ang-Sheng Institute of Atmospheric Physics Chinese Academy of Sciences Beijing 100029 China Graduate University of the Chinese Academy of Sciences Beijing 100049China Department of Atmospheric and Oceanic Science University of Maryland College Park Maryland 20742 USA

A cloud-resolving model simulation of a mesoscale convective system （MCS） producing torrential rainfall is performed with the finest horizontal resolution of 444 m. It is shown that the model reproduces the observed MCS, including its rainfall distribution and amounts, as well as the timing and location of leading rainbands and trailing stratiform clouds. Results show that discrete convective hot towers, shown in Vis5D at a scale of 2-5 kin, are triggered by evaporatively driven cold outflows converging with the high-θe air ahead. Then, they move rearward, with respect to the leading rainbands, to form stratiform clouds. These convective towers generate vortical tubes of opposite signs, with more intense cyclonic vorticity occurring in the leading convergence zone. The results appear to have important implications for the improvement of summertime quantitative precipitation forecasts and the understanding of vortical hot towers, as well midlevel mesoscale convective vortices.

关键词： torrential rainfall mei-yu front vortical hot towers mesoscale convective systems

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