两类厄尔尼诺事件发展年秋季印度洋海温异常特征对比

摘要

The present work investigates the different impacts of sea surface temperature (SST)anomalies over the tropical In-dian Ocean as associated with two types of El Ni~no events during boreal autumn,based on the observed data sets from 1951 to 2010.Here,we focus on the relationship between the Indian Ocean Dipole (IOD)and these two types of El Ni~no.It is shown that the positive IOD-like SST anomaly occurs for both EP and CP El Ni~no autumns,but with a different probability.Most of EP El Ni~no events are accompanied by a strong positive IOD-like SST anomaly.However,a weak positive IOD-like SST anom-aly appears for only half of the CP El Ni~no events.It seems that there is a strong relationship between the intensity of IOD and that of EP El Ni~no.That is,IOD tends to occur during the strong EP El Ni~no autumns,with a strong sinking current and neg-ative rainfall anomaly over the maritime continent.During the CP El Ni~no,however,the occurrence of IOD seems to be unre-lated with the strength of CP El Ni~no.The location of the CP El Ni~no is a possible key effect on the intensity of IOD in au-tumn.For the CP El Ni~no autumns when an obvious IOD appears,the warming SST anomaly is located slightly eastward over the central Pacific with a strong sinking current and severe drought over the maritime continent,as well as a significant easterly anomaly over the tropical Indian Ocean.While in the CP El Ni~no autumns during which no positive IOD-like SST anomaly oc-curs,the Pacific warming SST anomaly is located relatively further west.The very weak anomalous sinking motion seems lim-ited help to sustain the SST anomaly over the Indian Ocean.%基于1951—2010年逐月海气多要素观测资料，对比分析了两类厄尔尼诺事件发展年秋季印度洋的海温异常及大气响应特征，探讨了印度洋偶极子的发生与两类厄尔尼诺事件特征的可能联系。结果表明，两类厄尔尼诺事件的发展年均会出现印度洋偶极子，但出现的概率不同：大多数东部型厄尔尼诺事件都会伴有正位相印度洋偶极子发生；而仅一半的中部型厄尔尼诺事件期间会出现正位相印度洋偶极子的异常海温型，且强度较弱。从印度洋偶极子与两类厄尔尼诺事件的物理联系上看，东部型厄尔尼诺事件期间，印度洋偶极子的发生与其强度联系密切：印度洋偶极子发生在东部型厄尔尼诺事件较强期间，两者通过海洋大陆的异常强下沉运动及大范围负异常降水相联系；东部型厄尔尼诺事件偏弱时并无印度洋偶极子出现，海洋大陆异常下沉运动及负异常降水很弱。然而，中部型厄尔尼诺事件期间印度洋偶极子的发生与其强度并无显著的关系，而与太平洋高海温区的位置存在一定的可能联系：在有印度洋偶极子发生的中部型厄尔尼诺事件发展年秋季，热带太平洋异常高海温区的位置相对偏东，海洋大陆出现显著下沉运动和大范围负异常降水，热带东印度洋为大范围强异常东风控制；但无印度洋偶极子发生的中部型厄尔尼诺事件时，热带太平洋高海温区位置相对偏西，极弱的海洋大陆下沉支对热带印度洋异常海温作用非常有限。