全球变暖背景下ENSO特征的变化

发布时间：2018-10-11 12:58

【摘要】：利用1895~2014年Had ISST月平均海温资料和CO_2浓度加倍前后600年海气耦合模式CESM试验结果,对比分析了全球变暖前后厄尔尼诺-南方涛动(El Ni?o-Southern Oscillation,ENSO)特征(强度及其中心位置、生命期与频率)的变化及其可能原因.主要结论如下:全球变暖后,在观测和模拟中气候平均的海温增暖中心分别位于热带西太平洋(类拉尼娜型增暖)和热带东太平洋(类厄尔尼诺型增暖),引起热带太平洋低层东风信风相应地增强和减弱,从而改变了热带太平洋最强海气耦合的位置,决定了ENSO演变特征的不同变化.ENSO事件强度中心位置在类拉尼娜型增暖背景态下更倾向于发生在赤道太平洋中部,形成"中太平洋ENSO",而在类厄尔尼诺型增暖背景态下则更偏向赤道东太平洋,形成"东太平洋ENSO".两种气候态的改变都会造成全球变暖后El Ni?o事件生命期的明显延长,其中,类厄尔尼诺型增暖的影响更大,最大可延长约3个月,极端El Ni?o事件生命期的增长更显著.其主要原因是:全球变暖一方面使热带西太平洋异常西风更早出现,有利于El Ni?o事件的提早发生发展,另一方面会减小热带太平洋温跃层的平均深度和热带中东太平洋赤道内外平均海温梯度,分别减慢了海洋次表层负反馈Kelvin波的东传速率和减弱了El Ni?o暖信号的"放电"速率,使El Ni?o事件衰亡速度减缓,持续时间更长.另外,观测和模式结果均表明,ENSO事件强度和频率在全球变暖背景下明显增强和增多,并且类拉尼娜型和类厄尔尼诺型增暖背景态会分别导致极端La Ni?a事件和极端El Ni?o事件频率显著增多.本文研究结果很好地统一了观测和模式中不同气候背景态下ENSO特征变化的现象和机理,为理解和预估全球变暖后ENSO特征的变化及其气候影响奠定了重要的科学理论基础.
[Abstract]:Based on the monthly mean SST data of Had ISST from 1895 to 2014 and the results of 600 years of air-sea coupled model CESM test before and after the doubling of CO_2 concentration, the characteristics (intensity and central location) of the El Nino Southern Oscillation (El Ni?o-Southern Oscillation,ENSO) before and after global warming are compared and analyzed. Changes in life cycle and frequency and their possible causes. The main conclusions are as follows: after global warming, The observed and simulated mean SST warming centers are located in the tropical western Pacific (La Nina type warming) and the tropical eastern Pacific (El Ni 帽 o-like warming), respectively, resulting in the corresponding strengthening and weakening of easterly trade winds in the lower tropical Pacific. Therefore, the position of the strongest ocean-atmosphere coupling in the tropical Pacific is changed, which determines the variation of the evolution characteristics of ENSO. The ENSO event intensity center is more likely to occur in the central equatorial Pacific under the La Nina type warming background. "Central Pacific ENSO" is formed, while in the background of El Nino type warming, it is more inclined to equatorial eastern Pacific, forming "Eastern Pacific ENSO". The two climate changes will result in a significant prolongation of the lifetime of El Ni?o events after global warming. The effect of El Nino type warming is greater, the maximum extension is about 3 months, and the life cycle of extreme El Ni?o events is more significant. The main reason is that global warming, on the one hand, makes anomalous westerly winds in the tropical western Pacific appear earlier, which is conducive to the early occurrence and development of the El Ni?o event. On the other hand, the mean depth of the thermocline in the tropical Pacific and the mean SST gradient inside and outside the equatorial region of the tropical Middle Pacific Ocean are reduced, respectively, and the eastward propagation rate of the negative feedback Kelvin waves in the ocean subsurface and the "discharge" rate of the El Ni?o warm signal are reduced, respectively. El Ni?o events slow down and last longer. In addition, both observations and model results show that the intensity and frequency of ENSO events increase significantly in the context of global warming. The frequency of extreme La Ni?a events and extreme El Ni?o events increased significantly in the background state of La Ni 帽 a-like and El Nino like warming respectively. The results of this paper have well unified the phenomena and mechanisms of the changes of ENSO characteristics under different climatic background states in observations and models, and have laid an important scientific theoretical foundation for understanding and predicting the changes of ENSO characteristics and their climatic impacts after global warming.
【作者单位】：南京大学大气科学学院气候与全球变化研究院中国气象局-南京大学气候预测研究联合实验室;
【基金】：国家自然科学基金(41275069,41330420)、国家自然科学基金创新研究群体项目(41621005) 中央高校基本科研业务费专项资助
【分类号】：P732

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