孟加拉湾热带气旋活动及其对我国天气的影响

China suffers severe disasters every year from tropical cyclones, which include not only the typhoons in western North Pacific, but the cyclones in the Bay of Bengal also. The latter usually causes snowstroms in Tibetan Plateau, rainstorms in Southwest China and South China, even heavy rainfall events in the middle and lower Yangtze River reaches. In fact, the Bay of Bengal cyclone plays an important role in monsoon systems which affect China precipitaion greatly. The correct prediction for the Bay of Bengal cyclone activity is needed urgently in order to reduce and prevent its serious influence. However,a special operational forecast system for the Bay of Bengal cyclone is not built untill now in China, which is attributed to the insufficient knowledge on its activity mechanism to some extent.. As tropical cyclone, the study on the Bay of Bengal cyclones is far behind the one of typhoons in western North Pacific in China. Although there are many differences between the tropical cyclones in the two ocean bases, such as their activity features, affecting modes and physical processes etc. the related mechanism is still remained unknown now. So more attention should be paid on the Bay of Bengal cyclone study.. In this study, technical methods such as statistical analysis, cloud cluster tracking, air parcel trajectory tracer, dynamics diagnosis and numerical simulation etc. are employed to explore the activity features of cyclones in the Bay of Bengal and thier impacts on China precipitation at first,and then the impacting mode, physical process, dynamics condiction and the structure change of the Bay of Bengal cylones will be investigated. Finally, the mechanism of heavy rainfall induced by the cyclones is also to be disscussed. .The project aims to get better understanding on the mechanism of the Bay of Bengal cyclone impacts on China weather so as to provide theoretical basis and references for its forecasting level improvement. It also is helpful to suppluement and expand the operation and research on tropical cyclone to another ocean basis from the western North Pacific ocean in China.

我国是热带气旋（TC）影响重灾国，除西北太平洋（包括南海）台风外，孟加拉湾TC也对我国产生严重影响，常造成青藏高原暴雪、西南、华南暴雨、乃至长江中下游的强降水天气，在季风系统中扮演重要角色，其准确预报是防灾减灾的迫切需求。然而与台风相比，其研究和业务都相对落后，不但研究积累薄弱，预报业务也未全面开展。而其活动及对我国天气的影响机理又与台风有很大不同，这方面却认识不足。本项目拟采用统计分析、对流云团跟踪和气块轨迹计算、动力诊断和数值模拟等技术方法，首先分析孟加拉湾TC的活动规律及其对我国天气的影响特征，然后探讨其产生影响的方式、物理过程和动力学条件及影响TC的结构变化，在此基础上研究TC影响下我国强降水的发生机理。从而加强对孟加拉湾TC活动及影响的机理认识，形成孟加拉湾TC影响下我国强降水的概念模型。为建立其预报系统、提高其预报水平提供科学依据。还将有助于丰富和拓展我国TC的业务和研究领域。

孟加拉湾风暴是影响我国天气的除台风以外的又一热带气旋系统。由于生成海域地理环境的特殊性，孟加拉湾风暴对我国降水影响的物理方式与台风有所不同。本项目采用统计分析、动力诊断和数值试验等技术途径，研究了孟加拉湾风暴对我国降水的影响机制。.研究结果首先进一步明确了孟加拉湾风暴与中国降水的重要关系。指出风暴对青藏高原东南部、我国西南部、长江中下游部分地区的降水异常有重要影响，且对秋季降水的影响比初夏降水明显。孟加拉湾风暴影响我国降水的方式以远距离水汽输送以及分离云团北上为主，通过水汽热量输送加强高原切变或东移高原槽等西风带低值系统导致其降水增幅。.风暴影响我国降水的关键物理过程在于其能否与太平洋副热带高压（副高）或西风带南支槽共同配合，形成偏南风低空急流向我国输送低纬海洋的暖湿空气。研究发现，初夏（秋季）孟加拉湾风暴活动与青藏高原东部热源异常呈负（正）相关关系。青藏高原东部的热源异常主要通过影响青藏高压活动对孟加拉湾风暴活动产生影响。而风暴北上活动有利于水汽热量在青藏高原东南部汇聚和上升运动加强，从而影响局地天气和下游环流系统。对比风暴与台风影响我国降水的机制异同，发现风暴整体云系很少能到达我国，主要通过分离云团或输送水汽的方式影响我国，而台风则以其云系直接影响为主。相似之处在于二者均可与副高共同作用，为下游降水区提供水汽热量的远距离输送，导致降水系统的雨量增幅。.本项目在孟加拉湾风暴与我国降水关系及其影响机理等方面取得一些新的认识。发表学术专著1本，期刊论文15篇（SCI收录4篇）。发表硕士学位（博士）论文6（1）本。研发了“孟加拉湾风暴历史样本查询和预警概念系统”，并在国家级或地市级业务单位推广应用。为开展孟加拉湾海域热带气旋预报业务提供了科学依据和参考。