Meridional seesaw-like distribution of the Meiyu rainfall over the Changjiang-Huaihe River Valley and characteristics in the anomalous climate years
Meridional seesaw-like distribution of the Meiyu rainfall over the Changjiang-Huaihe River Valley and characteristics in the anomalous climate years
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DOI：
10.1007/s11434-007-0280-3
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发表时间：
2007-09
影响因子：
--
通讯作者：
Zhu Xiaying;He Jinhai;Wu Zhiwei
中科院分区：
文献类型：
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作者：
Zhu Xiaying;He Jinhai;Wu Zhiwei
尽管江淮流域梅雨降水在大部分年份具有同位相的空间变异性，但在某些年份，梅雨降水在江南和江北呈拉锯式分布，整个流域降水趋于正常，这不可避免地增加了降水短期预报的难度。为此，对1951-2004年6~7月的15个相关测站的降水资料进行了EOF分析，发现EOF2模基本上呈南北拉锯型，从而将梅雨型分为“北旱南涝(NDSF)”和“北涝南旱(NFSD)”两类。然后，作者利用NCEP再分析(版本1)和扩展的重建海温(版本2)研究了这两种异常类型发生时的海气特征。结果表明，在NDSF年，低层锋区和水汽辐合中心偏南，东亚副热带夏季风偏弱，西太平洋副热带高压和200hPa南亚高压偏南。前2月南北半球环型均较常年偏强，中国冬春季海温偏高，非可持续发展年海温偏高。此外，这种翘板状的梅雨降水分布可能会受到前一次ENSO事件的一定影响。
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.