海温对东亚夏季风年代际及冬季风年际变异的影响

【作者】 付建建；

【导师】 罗德海； 李双林；

【作者基本信息】 中国海洋大学 ， 气象学， 2009， 博士

【摘要】 本文从海温的异常出发，研究了其对东亚夏季风的年代际和东亚冬季风的年际变异的影响，借助大气环流模式和观测资料进行研究分析，主要得到以下结论：(1)用1979至1998年20年的气候月平均海温作为强迫场，来检验GFDLAM2模式对东亚冬、夏季风的模拟能力，发现该模式能较好的模拟东亚冬、夏季风的气候特征。(2)借助GFDLAM2模式，通过集合试验探讨了全球海温、热带海温、热带外海温变化对发生在1970s中后期的东亚夏季风的年代际变异的影响，结果显示全球海温在气候平均的变化的确能引起东亚夏季风的年代际变异和与之相关联的大气环流变化。相比热带外海温的影响，热带海温的变化对南亚高压、西北太平洋副热带高压、越赤道气流的变化的影响更为重要。(3)利用观测分析和AGCM试验，研究和讨论了2007／2008年强La Ni(?)a事件和前期北大西洋异常增暖对“0801”雪灾形成的影响。结果表明，强La Ni(?)a事件能部分解释“0801”南方偏冷和降水偏多及有关的部分大气环流异常，如高原南支槽加强、蒙古高压增强及西太平洋区域呈“负-正-负”西南-东北走向的异常环流型。但它不能解释乌拉尔地区的异常环流形势。进一步的分析认为，前期北大西洋的异常增暖对乌拉尔环流正异常的形成维持有重要影响。于是，“0801”雪灾的形成可能是包括强La Ni(?)a事件、北大西洋异常增暖等在内的多种因素共同作用的结果。(4)将ENSO的分为强、中等强度，合成分析了其对东亚冬季风环流的影响，东亚冬季风对强El Ni(?)o(La Ni(?)a)事件的响应上，数值模拟结果与已有资料的历史合成分析结果非常一致，对于中等强度的ENSO事件，东亚冬季风对其的响应要复杂的多，不能仅依赖ENSO信号来判断东亚冬季风环流情况，必须考虑其它因子的综合影响。更多还原

【Abstract】 East Asia experienced a significant interdecadal climate shift around the late 1970s, with more floods in the valley of the Yangtze River of central-eastern China and more severe drought in North China since then. Furthermore, snow and freezing-rain in January 2008 affected the Southern China and caused very serious damage. Whether global sea surface temperature (SST) has played a role in climate shift is unclear. In the present study, statistical analysis and numerical model are employed to investigate the impact of SST variations on the East Asian Monsoon, the main results are as follows:(1) The GFDL AM2 model simulates both the observed East Asian Summer Monsoon (EASM) and East Asian Winter Monsoon (EAWM) well.(2) The model results suggest that decadal global SST variations may have played a substantial role in this climate shift. Further examination of the associated atmospheric circulation shows that these results are physically reasonable. The interdecadal variation of tropical SST has more important effects on the climate shift of South Asia High(SAH), West Pacific Subtropical High(WPSH) and cross-equator air stream than extratropical SST.(3) By analyzing the observational data and conducting experiments in an AGCM GFDL AM2, we investigated the influence of the La Nina event. The results suggest that the strong La Ni(?)a can explain the colder climate and more precipitation than usual in South China, as well as the associated circulation anomalies like Mongolia Cold High. But, it can’t explain the enhancements of the west Pacific subtropical high and the blocking high over the Ural Mountains. Subsequently, we discussed the influence of the North Atlantic warmth using the results from a previous modeling study, and speculated that the warmth has played an important role for the maintenance of the persistent blocking over the Urals. Thus, it is concluded that the disastrous climate event happened in January 2008 may be resulted from the coordinate interaction of several factors including strong La Nina and North Atlantic warmth. (4) The response of EAWM to ENSO events are analyzed by using the composite method based on the Nino 3.4 Index and NCEP/NACR reanalysis data with four categories of strong El Ni(?)o (La Ni(?)a) and moderate El Nino (La Ni(?)a) events. The results suggest that when the El Ni(?)o (La Ni(?)a) events are not strong, other factors may partly have influence the response of atmosphere on ENSO events.更多还原