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气象:2021,47(11):1347-1358
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2019年江淮流域梅雨异常特征及成因分析
牛若芸,周兵
(国家气象中心,北京 100081;国家气候中心,北京 100081)
Analysis of Abnormal Characteristics and Causes of Meiyu over the Yangtze-Huaihe River Basin in 2019
NIU Ruoyun,ZHOU Bing
(National Meteorological Centre, Beijing 100081;National Climate Centre, Beijing 100081)
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投稿时间:2020-07-14    修订日期:2021-03-19
中文摘要: 利用梅雨监测、降水量观测以及NCEP大气再分析和海表温度等资料,对2019年江淮流域梅雨异常特征及其大尺度环流成因进行了分析研究,结果表明: 2019年江淮流域梅雨季入梅日期偏晚、长度偏短,梅雨量呈南多北少分布且总体偏少,并且是1951年以来梅雨带在长江以南停滞结束时间最晚的一年。三个子区中,江南区和长江中下游区梅雨期基本同步,江淮区出现空梅。6月上旬末至中旬前期冷空气势力的增强,阻碍和延后了东亚夏季风季节性北进的进程,导致了东亚大气环流型由冬季向初夏季转换时间偏晚及江淮流域入梅偏晚。5—6月印度洋海温偏暖(IOBW指数正异常)、南亚60°~80°E地区对流层中上层经向温度梯度逆转(由负转正)日期偏晚对2019年江淮流域入梅偏晚具有较好的超前指示性能。2019年梅雨季高层南亚高压东部脊和东亚西风急流偏南,中层亚欧中高纬环流经向度偏大、副热带高压西部脊偏南、澳大利亚东侧范围内位势高度偏高,低层东亚夏季风强度偏弱、前沿位置偏南。在上述多个大尺度环流系统异常特征共同影响下,江淮流域的长江中下游沿江以南地区处于高层强辐散和低层水汽通量经向强辐合的叠置区中,非常有利于垂直上升运动发展和强降雨的形成,从而导致了梅雨量南多北少的分布特征。
Abstract:Based on the Meiyu monitoring data, precipitation observation, NCEP reanalysis data and sea surface temperature data, the abnormal characteristics of Meiyu over the Yangtze-Huaihe River Basin (YHRB) in 2019 and its causes of large-scale circulation are analyzed. The results are as follows. The abnormal characteristics of the 2019 Meiyu obviously showed that the Meiyu onset date was later than normal with a shorter duration. The Meiyu rain was generally less than normal, presenting a distribution pattern of the more in the south and the less in the north of the Yangtze River over YHRB. Since 1951, the 2019 Meiyu belt stagnated the longest time in the south of the Yangtze River. Among the three subareas, the Meiyu period in the middle and lower reaches of Yangtze River was almost simultaneous with that in the south of Yangtze River, and the Yangtze-Huaihe River Subarea did not receive Meiyu obviously. Due to the periodical enhancement of the cold air from 8 to 15 June, the seasonal northward of East Asian summer monsoon was impeded and delayed, leading to the late conversion of the circulation pattern in East Asian from winter to early summer and also the late onset of Meiyu over YHRB. It can be regarded as the precursory signals of Meiyu onset date later over YHRB in 2019 that the sea surface temperature in Indian Ocean was warmer than normal in May-June and the reverse date of meridional temperature gradient of the middle-upper troposphere, was later over 60°-80°E of South Asia. Compared with climate mean state, the eastern ridge of South Asian high and East Asia westerly jet were southward in upper air, the circulation meridionality in the middle-high latitude in Eurasia was stronger and the western ridge of Northwest Pacific subtropical high was southward and the geopotential height east of Australia was higher at middle level, the strength of the low-level East Asia summer monsoon was weaker and the northernmost of the monsoon was southward. As a result of the combined influence of the above-mentioned abnormal characteristics, the south of the Yangtze River over YHRB was under the control of the strong divergence at high level and the strong meridional gradient convergence of vapor flux at low level, which is greatly conducive to the development of vertical upward movement and the occurrence of heavy rainfall, contributing to the distribution of the Meiyu precipitation in 2019 with the more in the south and the less in the north of the Yangtze River over YHRB.
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基金项目:国家重点研发计划(2018YFC1507703)资助
引用文本:
牛若芸,周兵,2021.2019年江淮流域梅雨异常特征及成因分析[J].气象,47(11):1347-1358.
NIU Ruoyun,ZHOU Bing,2021.Analysis of Abnormal Characteristics and Causes of Meiyu over the Yangtze-Huaihe River Basin in 2019[J].Meteor Mon,47(11):1347-1358.