| 冬季赤道太平洋不同类型海温异常表征指数的再构建 |
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| 引用本文： | 王美,管兆勇,皮冬勤.冬季赤道太平洋不同类型海温异常表征指数的再构建[J].大气科学学报,2016,39(4):455-467. |
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| 作者姓名： | 王美 管兆勇 皮冬勤 |
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| 作者单位： | 南京信息工程大学气象灾害教育部重点实验室/气候与环境变化国际合作联合实验室/气象灾害预报预警与评估协同创新中心;台州市气象局;福建省气象信息中心 |
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| 基金项目： | 国家自然科学基金重点资助项目(41330425);公益性行业(气象)科研专项(GYHY201406024) |
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| 摘 要： | 利用1963—2013年Hadley中心月平均海表温度资料,以及NCEP/NCAR再分析资料,根据两类厄尔尼诺事件发生时北半球冬季赤道太平洋地区海温异常的不同空间分布特征,即赤道中太平洋CP型和东太平洋EP型海温异常空间分布,从寻找与之相似的空间型角度出发,设计了一组新的海温异常指数I_(CP)和I_(EP)。与以往ENSO指数相比,新指数组I_(CP)和I_(EP)不仅表示了空间上相互独立的海温异常分布,而且在相同的研究时段内,因时间域上相互独立而能更好地表征和区分两类El Ni?o/La Ni?a事件。据此,采用该新指数组探讨了与中部型和东部型海温异常事件相关的热带太平洋的主要海气耦合特征。结果表明,与传统的东部型El Ni?o事件发生时最大暖海温中心位于赤道东太平洋地区不同,中部型El Ni?o事件,异常增暖中心位于赤道中太平洋。中部型时异常Walker环流的上升支向西偏移,异常降水集中于热带中太平洋,不似东部型时异常限定于赤道东太平洋地区。不论哪类事件,海洋性大陆均可受到影响,即CP或EP型El Ni?o发生时,海洋性大陆区域降水偏少。但比较而言,中部型ENSO对海洋性大陆区域的影响更大。
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| 关 键 词： | 北半球冬季 中部型和东部 型ENSO 海温异常指数 海洋性大陆 |
| 收稿时间： | 2015/1/23 0:00:00 |
| 修稿时间： | 2015/4/6 0:00:00 |
Reconstruction of equatorial Pacific SST anomaly indices for two types of ENSO during boreal winter |
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| WANG Mei,GUAN Zhaoyong and PI Dongqin.Reconstruction of equatorial Pacific SST anomaly indices for two types of ENSO during boreal winter[J].大气科学学报,2016,39(4):455-467. |
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| Authors: | WANG Mei GUAN Zhaoyong and PI Dongqin |
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| Institution: | WANG Mei;GUAN Zhaoyong;PI Dongqin;Key Laboratory of Meteorological Disaster,Ministry of Education(KLME)/Joint International Research Laboratory of Climate and Environment Change(IL-CEC)/Collaborative Innovation Center on Forecast and Evaluation of Meteorological Disasters(CIC-FEMD) ,Nanjing University of Information Science &Technology;Taizhou Meteorological Bureau;Fujian Meteorological Information Center; |
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| Abstract: | ENSO is the strongest interannual variability in our climate system.Recently,it has been found to vary as two types in spatial terms;the Central Pacific (CP) type,whose SST anomalies (SSTAs) are strongest in the central Pacific;and the Eastern Pacific (EP) type,characterized by SSTAs being strongest in the eastern equatorial Pacific.These two types of El Niño involve different teleconnections and climatic impacts,as the intensity and location of their associated SST-induced heating are different.Many studies have pointed out that CP El Niño events have increased in frequency in recent decades.Several kinds of indices have been designed for different types of El Niño events.For instance,the El Niño Modoki index (EMI) captures the second EOF pattern of equatorial Pacific SST anomalies.Another somewhat complicated index pair called the Central and Eastern Pacific Index (CPI/EPI),which is also an EOF-based index but with the SSTA related to the Niño1+2 or Niño4 index removed,has also been put forward.The most striking difference between the two types of El Niño is the longitudinal displacement of maximum anomalous SST along the equator in their mature stages.Motivated by this method of classification,we redefined two indices of SST anomalies,i.e.,ICP and IEP,for describing CP and EP El Niño/La Niña events and their interactions during boreal winter,by using both NCEP/NCAR reanalysis data and SST data from the Hadley Centre,for the period 1963-2013.This index pair was reconstructed based on the function for the CP pattern that changes with longitude and is perpendicular to the function for the EP pattern.Compared to other El Niño indices proposed previously,we found that the new indices can be used for better separating EP-type ENSO events from CP-type events,both spatially and temporally.The major features of air-sea coupling in the tropical Pacific related to CP-and EP-type events were investigated using the two new indices.It was found that these two distinct types of ENSO events demonstrate different periodic variation.Specifically,although they both exhibit 2-7- and 10-15-year oscillations in the tropical SSTA field,the decadal (10-15-year) variations for CP-type ENSO events are more dominant.It was also found that the anomalous warming center of CP-type El Niño appears in the central equatorial Pacific as expected,which is quite different from canonical EP-type El Niño events with their largest warm centers located in the eastern equatorial Pacific.Consequently,during CP-type events,the ascending branch of Walker circulation shifts farther west than normal,resulting in rainfall intensification mainly over the central tropical Pacific.However,when EP-type El Niño events occur,anomalous ascending motion is observed in the eastern equatorial Pacific,along with increased rainfall.Interestingly,during boreal winter,both types of El Niño can affect the Maritime Continent,but the CP type more strongly.Specifically,the Maritime Continent receives less than normal rainfall.Both of the reconstructed SSTA indices developed in this study are expected to be highly useful for monitoring ENSO events,and helpful in improving our understanding of the similarities and differences in the influence of CP-and EP-type ENSO events on climate variation at the global and regional (particularly East Asia) scale. |
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| Keywords: | boreal winter CP ENSO EP ENSO SSTA index Maritime Continent |
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