王钦,李双林,付建建,李国平. 2012. 1998和2010年夏季降水异常成因的对比分析:兼论两类不同厄尔尼诺事件的影响[J]. 气象学报, 70(6):1207-1222, doi:10.11676/qxxb2012.102
1998和2010年夏季降水异常成因的对比分析:兼论两类不同厄尔尼诺事件的影响
On the formation of anomalous summer precipitation in the years of 2010 and 1998: A comparison of the El Nino’s impact between Modoki and typical El Nino cases
投稿时间:2011-06-13  修订日期:2012-04-17
DOI:10.11676/qxxb2012.102
中文关键词:  厄尔尼诺和中部型厄尔尼诺, 长江中下游夏季降水, 西北太平洋异常反气旋, 个例对比
英文关键词:El NiNo and El NiNo Modoki, Summer rainfall in the middle and lower reaches of the Yangtze River, The western North Pacific anticyclone, Case comparison
基金项目:科技部公益性(气象)行业专项(GYHY201006022、GYHY200906018)
作者单位
王钦 成都信息工程学院, 大气科学学院, 成都, 610225
中国科学院大气物理研究所, 竺可桢 南森国际研究中心和东亚区域气候与环境重点实验室, 北京, 100029
中国民用航空飞行学院, 广汉, 618307 
李双林 中国科学院大气物理研究所, 竺可桢-南森国际研究中心和东亚区域气候与环境重点实验室, 北京, 100029 
付建建 中国科学院大气物理研究所, 竺可桢-南森国际研究中心和东亚区域气候与环境重点实验室, 北京, 100029 
李国平 成都信息工程学院,大气科学学院,成都,610225 
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中文摘要:
      1998和2010年夏季长江流域均发生了明显的洪涝灾害,且都是厄尔尼诺事件的次年(衰亡位相)。不同的是:1997/1998年冬季的厄尔尼诺事件是传统东部型,而2009/2010年冬季的厄尔尼诺事件是中部型(EL NiNo Modoki)。首先利用中国160个台站月降水观测资料,对比了1998和2010年降水异常情况,结果显示除长江流域多降水这一共同特征外,1998和2010年降水分布还存在一定差异。利用NCEP/NCAR再分析资料,对比了大气环流异常特征。结果表明:与1998年相比,2010年西北太平洋对流层低层异常反气旋中心位置偏北偏西,西太平洋副热带高压偏强、脊线偏北,使得南海—孟加拉湾西南风减弱而东亚南风加强,导致自印度洋、南海向内陆的水汽输送减少,而自西太平洋的水汽输送增加并输送到偏北的位置,雨带比1998年偏北,中国西南地区降水比1998年偏少。进一步分析厄尔尼诺的影响, 揭示环流形势的变化与中部型厄尔尼诺年赤道太平洋异常上升气流比传统厄尔尼诺年偏西、西太平洋异常下沉气流随之变化有关。利用GFDL大气环流模式AM2.1,进行了给定1998和2010年实际观测海温强迫的试验,显示海温差异能够部分解释观测到的环流异常。最后,将这两个个例与历史合成进行了比较,发现2010年与历史合成的中部型厄尔尼诺存在较大差异,表明中部型厄尔尼诺对中国夏季降水的影响比以前所认识的要复杂。
英文摘要:
      In the summers of 1998 and 2010, severe floods occurred in the middle and lower reaches of the Yangtze River. Although both the summers follow an El NiNo event, difference between the events is significant. The 1997/1998 El NiNo is a conventional one with warming in the central eastern Pacific whereas the 2009/2010 event is an El NiNo Modoki with warming in the central Pacific. In this study, summer rainfall anomalies in China in the two years are first compared by using the gauged rainfall dataset in 160 stations within mainland China with each other. The results show a significant difference. To understand the underlying mechanism for the difference, the atmospheric monsoonal circulation systems, particularly the western North Pacific anticyclone (WNPAC) and the western Pacific subtropical high (WPSH) as well as the lower level air flow, are compared by using the NCEP/NCAR reanalysis data. The results display that the WNPAC in 2010 is stronger, in comparison with 1998, in addition to a shift to the northwest, causing weakened southwesterly in the region from the Bay of Bengal to the South China Sea but intensified southerly in eastern China. This results in less water vapor transport from the tropical Indian Ocean and the South China Sea but more from the western subtropical Pacific to East Asia. Subsequently, the rainfall band in 2010 shifted northward. Difference in the WNPAC is caused by the anomalous ascending motion associated with the different warming location in the two El NiNo events from one another. Furthermore, the role of tropical SSTs in modulating these differences is investigated by conducting sensitive experiments using the atmospheric model, GFDL AM2.1. Two kinds of experiments are performed, one with the observed monthly SSTs and the other with the persistent June SSTs in summer for the two years. The results suggest that the primary difference in the monsoonal circulation system in the two years is well simulated. It is concluded that the difference in El NiNo events shapes the rainfall patterns in the two years of 1998 and 2010. At last, the case of 2010 is compared with the composite of the historical El NiNo Modoki events, and difference is significant. This indicates that the impact of El NiNo Modoki events is more complicated than that revealed previously.
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