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Meridional seesaw-like distribution of the Meiyu rainfall over the Changjiang-Huaihe River Valley and characteristics in the anomalous climate years
作者姓名:ZHU  XiaYing  HE  JinHai  WU  ZhiWei
作者单位:[1]Key Laboratory of Meteorological Disaster (KLME), Nanjing University of Information Science & Technology, Nanjing 210044, China [2]State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of AtmosphericPhysics, Chinese Academy of Sciences, Beijing 100029, China
基金项目:Supported by the National Natural Science Foundation of China (Grant No. 40605022), the National Basic Research Program of China (Grant No. 2006CB403607), and the Key Project of the Ministry of Science and Technology, China “South China Sea Monsoon Experiment (SCSMEX)”
摘    要:Although Meiyu rainfall has its in-phase spatial variability over the Changjiang-Huaihe River Valley (CHRV) in most years, it is distributed in some years like a seesaw to the north and south of the Changjiang River, when the precipitation tends to be nearly normal throughout the valley, which would inevitably increase difficulties of making short-term prediction of the rainfall. For this reason, EOF analysis is made on 15 related stations’ precipitation from June to July during 1951─2004, revealing that the EOF2 mode shows largely a north-south seesaw-like pattern, and thereby classifying Meiyu patterns into two types: "northern drought and southern flood (NDSF)" and "northern flood and southern drought (NFSD)". Afterwards, the authors investigated ocean-atmospheric characteristics when these two anomalous types occured using the NCEP reanalysis (version 1) and the extended reconstructed SSTs (version 2). The results show that in the NDSF years, the low-level frontal area and moisture convergence center lie more southward, accompanied by weaker subtropical summer mon- soon over East Asia, with the western Pacific subtropical high and 200 hPa South Asia High being more southward. Both the Northern and Southern Hemisphere Annular Modes are stronger than normal in preceding February; SST is higher off China during boreal winter and spring and the opposite happens in the NFSD years. Also, this seesaw-form Meiyu rainfall distribution might be affected to some degree by the previous ENSO event.

关 键 词:气候反常  梅雨  长江-黄河流域  降雨  空间分布
收稿时间:2006-12-18
修稿时间:2006-11-18

Meridional seesaw-like distribution of the Meiyu rainfall over the Changjiang-Huaihe River Valley and characteristics in the anomalous climate years
ZHU XiaYing HE JinHai WU ZhiWei.Meridional seesaw-like distribution of the Meiyu rainfall over the Changjiang-Huaihe River Valley and characteristics in the anomalous climate years[J].Chinese Science Bulletin,2007,52(17):2420-2428.
Authors:Zhu  XiaYing  He  JinHai  Wu  ZhiWei
Institution:(1) Key Laboratory of Meteorological Disaster (KLME), Nanjing University of Information Science & Technology, Nanjing, 210044, China;(2) State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics, Institute of Atmospheric Physics, Chinese Academy of Sciences, Beijing, 100029, China
Abstract:Although Meiyu rainfall has its in-phase spatial variability over the Changjiang-Huaihe River Valley (CHRV) in most years, it is distributed in some years like a seesaw to the north and south of the Changjiang River, when the precipitation tends to be nearly normal throughout the valley, which would inevitably increase difficulties of making short-term prediction of the rainfall. For this reason, EOF analysis is made on 15 related stations’ precipitation from June to July during 1951–2004, revealing that the EOF2 mode shows largely a north-south seesaw-like pattern, and thereby classifying Meiyu patterns into two types: “northern drought and southern flood (NDSF)” and “northern flood and southern drought (NFSD)”. Afterwards, the authors investigated ocean-atmospheric characteristics when these two anomalous types occured using the NCEP reanalysis (version 1) and the extended reconstructed SSTs (version 2). The results show that in the NDSF years, the low-level frontal area and moisture convergence center lie more southward, accompanied by weaker subtropical summer monsoon over East Asia, with the western Pacific subtropical high and 200 hPa South Asia High being more southward. Both the Northern and Southern Hemisphere Annular Modes are stronger than normal in preceding February; SST is higher off China during boreal winter and spring and the opposite happens in the NFSD years. Also, this seesaw-form Meiyu rainfall distribution might be affected to some degree by the previous ENSO event. Supported by the National Natural Science Foundation of China (Grant No. 40605022), the National Basic Research Program of China (Grant No. 2006CB403607), and the Key Project of the Ministry of Science and Technology, China “South China Sea Monsoon Experiment (SCSMEX)”
Keywords:Meiyu  floods and droughts  spatial distribution  ocean-atmospheric singularities
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