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ISSN 1006-9895

CN 11-1768/O4

近50年华东地区夏季异常降水空间分型及与其相联系的遥相关
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国家科技支撑计划项目2007BAC29B02


Anomalous Summer Rainfall Patterns in East China and the Related Teleconnections over Recent 50 Years
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    摘要:

    利用中国华东地区91个站点1961~2007年夏季 (6~8月) 逐日降水资料和NCEP/NACR再分析资料, 用旋转经验正交函数 (REOF) 方法将华东地区夏季降水场分为5个区域, 即I区 (闽赣地区)、II区 (江南)、III区 (长江中下游地区)、IV区 (江淮) 和V区 (黄淮)。这5个区域的夏季降水周期显著不同, 当I区降水的年际周期性强 (弱) 时, II、III、IV、V区降水年际周期性弱 (强)。I~V区夏季降水的年代际及年际变率的年代际变化显著, 且在年代际降水较少或由多变少或由少变多的转换时段, 容易发生较大的年际变化。各区降水异常形成的局地成因有所差别。其中, 江南南部、江南、沿江 (长江中下游) 受低层异常反气旋控制, 该异常反气旋使得这些地区出现水汽辐散, 与异常的非绝热冷却结合, 造成异常下沉气流, 导致干旱发生。对于江淮之间的地区, 由南侧异常气旋性环流和北侧反气旋环流的西部辐散气流控制, 造成水汽向南北两侧辐散, 导致降水偏少; 对于黄淮地区干旱, 可归因于位于蒙古高原上的反气旋异常和位于西太平洋上的气旋性异常之间的异常偏北气流造成该地区水汽的异常辐散所致。华东5个区域的夏季降水和不同类型的遥相关有关。闽赣地区降水受欧亚-太平洋型 (EUP) 遥相关影响; 江南地区降水则可能受东亚-太平洋型 (EAP)/太平洋-日本型 (PJ) 影响, 亦与太平洋-北美型 (PNA) 存在可能的联系; 长江流域则可能受东大西洋型 (EA) 和EAP型影响; 江淮地区降水则明显地受EA/EUP和PJ/EAP的共同影响, 而黄淮降水则与源于地中海地区向东北传播且通过北极涛动 (AO) 产生影响的波列存在联系。这5个区域的夏季降水异常还和东亚地区位涡、 南海夏季风、 Niño3、Niño4区海温、西太平洋副高变动等因子有关。

    Abstract:

    Based on the daily summer (June-August) precipitation at 91 stations in East China from 1961 to 2007 and NCEP/NCAR reanalysis data, five subdivisions of summer precipitation in East China are divided by using rotated empirical orthogonal function (REOF) method. They are subdivision I (Fujian-Jiangxi), subdivision II (South of the Yangtze River), subdivision III (the middle and lower reaches of the Yangtze River), subdivision IV (Huaihe River), and subdivision V (Yellow River-Huaihe River). Anomalies of summer rainfall in these five subdivisions change in different ways on interannual time scale. When the interannual rainfall in subdivision I is more (less) than normal, and other subdivisions’precipitation is less (more) than normal. Both the interdecadal variations and the interdecadal changes of interannual variabilities of the precipitation are remarkable. The maximum interannual variability occurs in the period that the precipitation is less than normal, or in the transition periods that the precipitation become more or less. The rainfall anomalies in different subdivisions are different. The area of Fujian-Jiangxi, the south of the Yangtze River, the middle and lower reaches of the Yangtze River have less rainfall, which is because an anomalous anticyclone causes moisture to diverge outward from these subdivisions. These anticyclonic circulation anomalies along with the abnormal diabatic cooling induce the anomalous descent of air, and henceforth lead to droughts in these subdivisions. In the region between the Yangtze River and the Huaihe River the divergent flow prevails. This divergent flow is caused by the divergence of the gear-coupled anomalous anticyclone north of the Huaihe River and anomalous cyclone south of the Yangtze River. This divergent flow transports the moisture outward from this region, reducing the precipitation there. In the Yellow River-the Huaihe River area, the divergent airflow exists between the anomalous anticyclone over the Mongolian Plateau and the abnormal cyclone over the western Pacific. It is also found that the five patterns of the summer rainfall anomalies are related to different teleconnections. Precipitation anomalies in Fujian and Jiangxi are influenced by Eurasia-Pacific (EUP) teleconnection. JJA (June-July-August) mean precipitation anomalies in the area south of the Yangtze River may be partly affected by East Asia-Pacific (EAP)/Pacific-Japan (PJ)/Pacific-North America (PNA) teleconnections. The JJA precipitation anomalies in the area along the Yangtze River are possibly influenced by East Atlantic (EA)/EAP teleconnection. It is apparently seen that the rainfall anomalies around the Huaihe River are influenced by EA/EUP and PJ/EAP teleconnections. The summer rainfall anomalies in the regions between the Yellow River and Huaihe River are likely to be influenced by the wave train perturbations propagating from the Mediterranean northeastward and influenced by AO (Arctic Oscillation). The summer rainfall anomalies in the five subdivisions are also found to be related to the potential vorticity anomalies in East Asia, anomalous activities of the South China Sea summer monsoon, the sea surface temperature anomalies in the Niño3 and Niño4 regions, and the variabilities of the western Pacific subtropical high.

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金大超,管兆勇,蔡佳熙,等.近50年华东地区夏季异常降水空间分型及与其相联系的遥相关.大气科学,2010,34(5):947~961 JIN Dachao, GUAN Zhaoyong, CAI Jiaxi,et al. Anomalous Summer Rainfall Patterns in East China and the Related Teleconnections over Recent 50 Years. Chinese Journal of Atmospheric Sciences (in Chinese),2010,34(5):947~961

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  • 在线发布日期: 2011-12-06
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