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江淮梅雨期强降水和大气不同时间尺度波动的关系
周宁芳,李勇,贾小龙
1.国家气象中心,北京 100081;2. 南京信息工程大学/气象灾害预报预警与评估协同创新中心,江苏 南京 210044;3. 国家气候中心/中国气象局气候研究开放实验室,北京 100081
摘要:
中国的江淮梅雨具有多时间尺度特征,利用1979—2017年欧洲中期预报中心逐日再分析资料(ERA-interim)和台站逐日降水观测数据,采用滤波和合成分析等统计方法,分析了江淮梅雨期间不同时间尺度强降雨过程的特征,对比研究了不同时间尺度强降水对应的大气环流系统波动的演变特征。研究表明江淮梅雨降水集中期开始前1~9天和10~20天尺度的强降水首先增多,而21~30天时间尺度的强降水在降水集中期开始增多。低频周期波动(10~20天和21~30天)比天气尺度波动可以提供更持续和更深厚的暖平流输送,触发持续时间更长的垂直运动和水汽输送,有利于持续性强降水的发生。与1~9天天气尺度波动相关的强降水主要与上游自中亚经青藏高原向下游传播并不断发展加强的Rossby波能量传播有关,青藏高原对天气尺度涡旋的增强有重要作用;对10~20天尺度强降水,高层中纬度东北亚低频反气旋环流西移南压,长时间维持在江淮地区,低层南海-西太平洋地区准双周振荡西北向传播,伴随西北太平洋副热带高压加强西伸是主要影响过程;对21~30天尺度强降水而言,江淮上空移动性环流不明显,高层反气旋性环流增强的过程与其北南两侧,即贝加尔湖及其以东地区气旋环流和南海-西太平洋气旋环流的发展移动有密切的联系,同时伴随了对流层中低层西北太平洋地区21~30 天尺度低频波的西北传播。
关键词:  江淮梅雨  强降雨  天气周期波动  低频波动
DOI:10.16032/j.issn.1004-4965.2021.002
分类号:
基金项目:
RELATIONSHIP BETWEEN HEAVY PRECIPITATION AND ATMOSPHERIC WAVE WITH DIFFERENT TIME SCALES DURING MEIYU PERIOD IN YANGTZE-HUAI RIVER REGION
ZHOU Ning-fang1,2,3, LI Yong1,2,3, JIA Xiao-lon4,5
1.National Meteorological Center, Beijing 100081, China528000, China;2.3. State Key Laboratory of Remote Sensing Science, Jointly Sponsored by Beijing Normal University and Institute of Remote Sensing and Digital Earth of Chinese Academy of Sciences, Beijing 100875, China;3.4. Beijing Engineering Research Center for Global and Remote Sensing Products, Institute of Remote Sensing Science and Engineering, Faculty of Geographical Science, Beijing Normal University, Beijing 100875, China;4.2. Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters, Nanjing University of Information Science & Technology, Nanjing 210044, China;5.3. National Climate Center, Beijing 100081, China
Abstract:
The heavy rainfall in the Yangtze-Huai Rive region during Meiyu period is subject to the influence of several different meteorological phenomena at different time scales. In the present study, we analyzed the characteristic of the heavy rainfall associated with synoptic, biweekly and 21-30-day background and compared the evolution characteristics of corresponding atmospheric circulation system by using the daily reanalysis data provided by the European Centre for Medium-Range Weather Forecast (ECMWF) and daily precipitation observational data from meteorological stations in China during 1979—2017. The results showed that heavy rainfall with synoptic and biweekly background are active before the concentration period of Meiyu in the Yangtze-Huai River region, while the heavy rainfall with 21-30-day background increases during the concentration period. The low frequency background (10-20-day and 21-30-day) can transport longer and thicker warm airstream than the synoptic distribution does, and trigger longer vertical ascending motion and continuous water vapor, facilitating the development of continuous rainfall processes. Synoptic-scale heavy rainfall is mainly related to the upstream propagation of Rossby wave energy from central Asia. The Qinghai-Tibet Plateau plays an important role in enhancing the synoptic scale vortex. Biweekly scale heavy rainfall is mainly related to the southwest movement of northeast Asia anticyclone, which later remains in the Yangtze-Huai River region for several days. It is also influenced by the northwest propagation of quasi-biweekly oscillations in the lower troposphere over the South China Sea and western Pacific region, and by the western extension of the subtropical high. For the 21-30-day-scale heavy rainfall, the circulation in the lower troposphere of the Yangtze-Huai Rive region is relatively stable; the anticyclone in the high troposphere enhancement is closely related to the development and movement of the circulations on both the north and the south side, and the northwest propagation of low frequency oscillations in the lower troposphere of the western Pacific region.
Key words:  Meiyu in the Yangtze-Huai River region  heavy precipitation  weather fluctuation  low frequency wave
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