【作者】 曹璐；

【导师】 江静； 任福民；

【作者基本信息】 南京大学 ， 气象学， 2011， 硕士

【摘要】 本文针对1950—2009年间的东部型(EP)和中部型(CP)ENSO事件,比较了目前国际上常用的ENSO监测指数对它们的监测能力。结果表明：对于EP-/CP-EN SO事件,单一的指数无法同时区分出这两种不同分布型的ENSO事件,其中Nino 3指数只能有效识别EP型ENSO事件,而Nino4指数则对CP型事件具有较强的监测能力。据此本文提出同时以Nino3指数和Nino4指数构建指数组的形式来监测不同类型的ENSO事件。进一步分析表明,该指标组能够较全面监测历史上发生的不同分布类型ENSO事件,且能准确判定事件的峰值强度、起止时间和成熟期等其它特征。在此基础上,本文分析了EP-/CP-ENSO事件的峰值时期以及发展消亡过程中,大气系统的温度场、高度场、风场及环流等特征的不同响应,建立了这两种类型ENSO事件的短期气候特征模型模,并结合2009/2010年的CP.EI Nino事件和2010/2011年CP.La Nina事件进行解释说明。主要结论包括：1)提出同时以Nino3指数和Nino4指数构建指标组的形式来监测不同类型ENSO事件,而目前美国、日本和中国国家气候中心采用的单一指数均不能对事件进行有效的分型,此外该指数还可以准确判定ENSO事件的峰值强度、起止时间和成熟期等其他特征。2)在1950—2009年这60年中发生了36次ENSO事件,其中EI Nino事件有19次,而La Nina事件只有17次。CP.EI Nino相对较多有11次；而在La Nina事件中,EP-La Nina的发生次数明显更多有11次。此外,从这些事件的年代际分布特征看,在1995年以前EP型ENSO事件偏多,而1995年以后CP型事件显著偏多。3)综合指标组定义的ENSO事件中,EP型事件和CP型事件之间的差异很大。大气系统在温度场、高度场、风场及环流等方面对这两种ENSO事件的响应也有显著的差别,海表热源东一西位置上的差异使得加热区发生变化,进而引起大气响应的不同。环流系统在赤道东太平洋靠近秘鲁沿岸(Walker环流的下沉区),出现与中太平洋大部分地区截然相反的影响是CP型事件的标志性特征。4)针对EP-El Nino事件和CP-La Nina事件平均生命期较长、EP-El Nino事件强度等级最高等方面是正反馈的作用。建立EP-/CP-ENSO事件的短期气候特征模板,将这两种类型ENSO事件分开进行监测和预测十分必要且意义重大。更多还原

【Abstract】 Recent studies reavealed that two types of ENSO events were existed:the Eastern-Pacific (EP) and Central-Pacific (CP) type. Therefore, the study examined the monitoring ability of several current operational ENSO indices. The results indicated that single index could not distinguish the type of ENSO events as EP or CP from the historical ENSO events during 1950-2009. The Nino 3 index might only suit for monitoring the EP ENSO, while the Nino 4 index might for the CP type. Therefore, for the purpose of not only capturing the occurrence of ENSO event but also distinguishing its type, a new monitoring index group constructed by both Nino 3 and Nino 4 indices was proposed. Further analysis confirmed that this index group could monitor different types of historical ENSO events with different spatial distribution of sea surface temperature. And it had a better performance in determining some characteristics of those events, including the peak intensity, onset, decay, mature phase, and so on.On this basis, this paper analyzed the different responses of atmospheric temperature field, height field, wind field, circulation field and other characteristics during the peak period and in the process from the development of EP-/CP-ENSO events to the extinction. Short-term climatic characteristics modes of the two types of ENSO events were established, and they are explained with the 2009/2010 CP-E1 Nino event and 2010/2011 CP-La Nina event. The main conclusions include:1) A target group of indices combining both Nino 3 and Nino 4 indices to monitor different types of ENSO events is proposed, while United States, Japan and China National Climate Center are using single index, which can not define the incident type effectively at present. In addition, this target group can accurately determine the peak intensity, beginning and ending time, maturity period, and other features of ENSO events.2) From 1950 to 2009, ENSO events have occurred 36 times, including 19 El Nino events, and 17 La Nina events. The frequency of CP-E1 Nino, which is 11 times, is relatively higher than EP-E1 Nino; while for La Nina, frequency of EP-La Nina is higher happened 1 ltimes. In addition, interdecadal distribution shows that, there are more EP-ENSO events before 1995, while more CP-ENSO events after.3) The EP-ENSO events and CP-ENSO events defined by the Composite Index are much different from each other. There are significant differences between the responses on the atmospheric temperature field, height field, wind field, circulation field, et aL The difference between east part and west part of the heat source of sea surface causes heating zones change, leading to different atmospheric response. In the eastern equatorial Pacific near the Peruvian coast (Walker circulation in the sink area), circulation system showing opposite effects to most parts of Pacific is a landmark feature of CP-type event.4) Facts that average lifetime and intensity of EP-E1 Nino events and CP-La Nina events show a significant positive relationship. It’s necessary to monitor and predict the two types of ENSO events separately, with establishing the short-term climatic characteristics mode for EP-/CP-ENSO events.更多还原