热带西太平洋上层热含量年际变化的区域性特征

REGIONAL CHARACTERISTICS OF INTER-ANNUAL VARIATIONS IN THE UPPER LAYER HEAT CONTENT OVER THE TROPICAL WESTERN PACIFIC OCEAN

采用 1 980— 2 0 0 1年的XBT月平均海洋上层温度资料对与ElNi no和SouthernOscilla tion(ENSO)相关的热带西太平洋温跃层以上 (上层 )热含量年际变化的区域特征进行了研究。从热带西太平洋温跃层和上层热含量南北不对称的气候态出发 ,将其分为“北部”、“赤道”和“南部”三个子区域。发现热带西太平洋上层热含量的调整要领先于Nino3区 ,并且其释放的热量与ElNi no事件的强度成正比 ,而ElNi no事件爆发前热带西太平洋上层热量积累的多少对ElNi no事件强度没有明显的影响 ;热带西太平洋赤道外区域也是ENSO热泵的一部分 ,其中北部子区域的上层热含量年际调整要超前于赤道和南部子区域 ,在热泵中起征兆的作用。通过热带西太平洋上层热含量距平场与Nino3指数的超前滞后相关关系分析发现 ,热带西太平洋上层热含量年际调整表现出明显的南北不对称 ,北部子区域内信号时间超前且涉及的空间范围广 ,南部时间上落后且空间上局限在一个窄带状区域内。热带西太平洋上层热含量年际调整的路径是 :热含量年际调整信号率先在太平洋北部子区域出现 ,然后发展到太平洋赤道和南部子区域 ,再沿赤道向东发展到东太平洋。

ENSO system behaves like a heat pumping: the equatorial ocean absorbs heat during the cold phase and pushes the heat to the subtropical ocean during the warm phase.The Pacific upper-layer thermal structure is asymmetric between northern equator and southern equator and the tropical western Pacific accumulates plentiful heat and the heat in off-equator domain is more abundant than in the equator domain.Do the off-equator west Pacific warm pool domains participate in the heat pumping? What are the regional characters of West Pacific warm pool heat content's inter-annual adjustment? By applying the XBT data sets (1980—2001),NCEP reanalysis of sea surface 10m wind fields,SOI index and Nino3 index,we investigated the inter-annual variation of heat content in the tropical western Pacific upper layer water (from the surface to thermocline).The tropical western Pacific is artificially divided into the northern,equatorial and southern sub-domains,with the northern and southern parts representing the northern and southern off-equator domains of western Pacific,respectively,according the climatologic meridional asymmetric structure of the tropical western Pacific thermocline. The relationship between the heat content released from the tropical Pacific during El Nio events and the intensity of El Nio events is found to have a linear dependence.The effect of heat content accumulated in the tropical western Pacific before the onset of El Nio on El Nio event's intensity is not very obvious.The two off-equatorial parts of the tropical western Pacific also participate in the ENSO related heat pumping; for instance,the northern part,which initializes the heat content adjustment,leads the Nino3 index by 10 months and leads the equatorial part and the southern part by 6 months. Regarding the relationships of leading and lagging correlation between the Nino3 index and the heat content anomaly in the tropical western Pacific,the inter-annual adjustment in the tropical western Pacific shows a distinct meridional asymmetric pattern.The heat content anomaly in the northern sub-domains,whose spatial area is wider than the southern one judged from the significantly correlated region,initialize the inter-annual adjustment of the tropical western Pacific.The southern sub-domain lags the northern one and is constrained in a narrow band.The effect of meridional wind variation is likely to generate the narrow band structure in the southern sub-domain referring to the relationships of leading and lagging correlation between SOI index and the heat content variation.The signature consequent diagram of the tropical western Pacific heat content anomalies indicates that the signal appears firstly in the northern sub-domain,then spreads to the equatorial and southern sub-domains,and extends eventually along the equator to the eastern tropical Pacific.