2018年浙江梅雨降水异常偏少的大尺度环流特征及前兆信号分析  

Analysis of Large-scale Atmospheric Circulation and Associated Precursory Climatic Signals for Exceedingly Less Meiyu Precipitation over Zhejiang in 2018

作　　者：马浩[1] 陈伯民[2] 樊高峰[1] 刘学华 肖晶晶[1] 高大伟[1] 殷悦 MA Hao;CHEN Bomin;FAN Gaofeng;LIU Xuehua;XIAO Jingjing;GAO Dawei;YIN Yue(Zhejiang Climate Center,Hangzhou 310052,Zhejiang,China;Shanghai Climate Center,Shanghai 200030,China;Lanxi Meteorological Bureau,Lanxi 321199,Zhejiang,China)

机构地区：[1]浙江省气候中心,浙江杭州310052 [2]上海市气候中心,上海200030 [3]兰溪市气象局,浙江兰溪321199

出　　处：《高原气象》2024年第4期933-954,共22页Plateau Meteorology

基　　金：浙江省自然科学基金联合基金重大项目(LZJMD24D050002);国家自然科学基金项目(42175056,41730959);浙江省基础公益研究计划项目(LGF19D050001,LGF22D050007);中国气象局预报员专项项目(CMAYBY2019-048);浙江省自然科学基金探索项目(LQ20D050004);浙江省气象局重点项目(2020ZD14)。

摘　　要：2018年浙江梅雨降水异常偏少,梅雨期平均环流特征欧亚中高纬度为“两槽一脊型”,西太平洋副热带高压(以下简称西太副高)偏东偏北,东亚高空急流偏北,浙江以南缺少低空急流的支持,不利于形成持续降水。6月上、中旬水汽输送不足、南北气流辐合较弱、东亚高空急流偏南、南海夏季风偏强、印度季风偏弱是梅雨开始偏晚的重要原因。梅汛期主要形成了三次降水过程(过程Ⅰ、过程Ⅱ和过程Ⅲ)和一次降水间歇过程,过程Ⅰ和过程Ⅱ表现为南北气流辐合型降水,过程Ⅲ为台风降水。系统分析了与不同过程相对应的大尺度环流及其演变特征,发现由于冷空气活动偏弱、南海夏季风偏强、西南水汽输送偏弱,过程Ⅰ的强度强于过程Ⅱ。在环流分析基础上,进一步挖掘与浙江梅雨有密切关联的海洋、大气和陆面信号,发现对该年梅雨异常偏弱有重要指示意义的前兆信号为冬、春季Ni?o关键区海温指数为正异常且北太平洋中部海温呈现负异常、冬季西南印度洋海温为正异常、春季喀拉海-巴伦支海海冰偏少、4-5月南半球环状模指数和北极涛动指数分别处于正位相和负位相。基于浙江梅雨序列,依托相关系数和同号率两个指标筛选出从前冬到春季稳定维持或有所增强的气候信号,利用多元线性回归、多因子综合判别、联合诊断三种方法分别构造可冬季发布和春季发布的梅雨预测模型,发现线性模型整体上能够较好地预测梅雨降水距平,特别是对降水偏少情形指示意义突出。Meiyu precipitation of Zhejiang province was abnormally less than usual in 2018.During the Meiyu period,mean feature of large-scale circulation in mid-high latitude on 500 hPa exhibited a“trough-ridge-trough”pattern,while in low latitude,western Pacific subtropical High(WPSH)marched eastward and northward.Moreover,the upper-layer westerly jet over East Asia located northward and low-level jet supply south of Zhejiang was not sufficient.All the factors above worked together to form weak Meiyu.Inadequate moisture transport in the first and second ten days of June,inferior convergence of north and south flows,southward-placed westerly jet over East Asia,stronger South China Sea summer monsoon(SCSSM),and weaker Indian monsoon acted jointly to cause a late Zhejiang Meiyu.There were three rainfall processes(process I,process II,and process III)and a time with few precipitation during the entire Meiyu stage.The formation of process I and II could be attributed to meeting of northward and southward air flows,while the essence of process III was typhoon-induced convection.The spatiotemporal variation of large-scale circulation associated with different processes was investigated comprehensively,and the result indicated that compared to process I,precipitation intensity of process II was very limited because of the forceless cold air invasion,more powerful SCSSM,and feeble transport of southwest moisture.Furthermore,the impact of precursory oceanic,atmospheric,and land signals on Meiyu was analyzed,and found that the primary climate characteristics were positive Niño index and negative North Pacific sea surface temperature(SST)anomaly in winter and spring,warm SST over southwest Indian Ocean in winter,decreased sea ice for the Kara-Barents Sea in spring,and Southern Annular Mode and Arctic Oscillation in the positive and negative phases respectively during April-May.Based on the monitoring time-series of Zhejiang Meiyu,the stable or strengthened climatic factors from winter to spring were extracted with two indices of

关 键 词：梅雨降水 降水过程 大尺度环流演变 前兆信号 统计预测模型 

分 类 号：P461[天文地球—大气科学及气象学]