1991-1995 長聖嬰個案診斷分析
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2012
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聖嬰現象的周期一般為1-2年，1991-1995年出現長達五年的聖嬰，是過去百年觀測紀錄最長的聖嬰個案。目前雖然已有些研究探討此個案，但此長生命聖嬰現象如何維持？全球暖化或太平洋年代際變化與此個案的關係？目前尚無清楚的答案。本研究主要利用SODA （Simple Ocean Data Assimilation） 2.0.2觀測資料以及濾波方法探討全球暖化與太平洋年代際變化對1991-1995 聖嬰個案的影響，並透過混合層熱量收支了解此長聖嬰個案維持的物理機制。
從海洋垂直結構與大氣環流發現此聖嬰為中太平洋型聖嬰與東太平洋聖嬰兩類型聖嬰的混合，前期（1991-1992）大氣與海洋結構近似東太平洋型聖盛嬰，後期（1993-1995）類似中太平洋型聖嬰。濾波分析顯示太平洋年代際變化對此聖嬰週期的延續具關鍵性影響，但全球暖化線性增溫的影響則不明顯。混合層熱量收支得到太平洋年代際變化主要透過氣候平均垂直運動之垂直溫度平流項與氣候平均緯向運動之南北向溫度平流項延長此聖嬰的周期。
A record-breaking unusual prolonged El Niño event was identified during 1991-1995. While many previous studies had devoted the duration of ENSO （El Niño and Southern Oscillation）, the physical mechanisms associated with this longlife El Niño is still unclear. A mixed layer heat budge is conducted to specify the physical processes to maintain n the prolonged El Niño event by diagnosing the SODA （Simple Ocean Data Assimilation） 2.0.2 data. The relative contribution of decadal variation （≧ 8years） and linear warming trend to the duration of 1991-1995 El Niño is particularly focused on in this study. The spatiotemporal evolution of the large-scale oceanic and atmospheric condition reveals that the 1991-1995 El Niño is likely a mixed of the Central-Pacific （CP） and Eastern-Pacific （EP） types of El Niño, which resembles the EP El Niño during 1991-1992 and CP El Niño for the other else. It was found that that the decadal variation is tightly related with the duration of 1991-1995 event, whereas, the influence of the linear warm trend is insignificant. The mixed layer heat budget further suggests that the decadal variation tend to prolong the El Niño duration trough the vertical temperature advection and meridional temperature advection by the climatologically mean vertical and meridional velocity respectively.
A record-breaking unusual prolonged El Niño event was identified during 1991-1995. While many previous studies had devoted the duration of ENSO （El Niño and Southern Oscillation）, the physical mechanisms associated with this longlife El Niño is still unclear. A mixed layer heat budge is conducted to specify the physical processes to maintain n the prolonged El Niño event by diagnosing the SODA （Simple Ocean Data Assimilation） 2.0.2 data. The relative contribution of decadal variation （≧ 8years） and linear warming trend to the duration of 1991-1995 El Niño is particularly focused on in this study. The spatiotemporal evolution of the large-scale oceanic and atmospheric condition reveals that the 1991-1995 El Niño is likely a mixed of the Central-Pacific （CP） and Eastern-Pacific （EP） types of El Niño, which resembles the EP El Niño during 1991-1992 and CP El Niño for the other else. It was found that that the decadal variation is tightly related with the duration of 1991-1995 event, whereas, the influence of the linear warm trend is insignificant. The mixed layer heat budget further suggests that the decadal variation tend to prolong the El Niño duration trough the vertical temperature advection and meridional temperature advection by the climatologically mean vertical and meridional velocity respectively.
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長週期聖嬰, 全球暖化, 年代際變化, 混合層熱量收支, ENSO, Mixed layer heat budge, Decadal variation, linear warming trend