近年来厄尔尼诺期间北赤道流输运的年际变化

Interannual variations of the North Equatorial Current transport in recent years during El Ni?o events

为了研究近年来厄尔尼诺期间北赤道流输运的年际变化,本文利用海洋客观分析数据MOAA GPV（Grid Point Value of the Monthly Objective Analysis）以及P-vector方法计算了北太平洋绝对地转流,探讨了2001~2013年期间厄尔尼诺与北赤道流输运之间的关系。在此期间发生的4次厄尔尼诺事件中,北赤道流输运在2002~2003、2006~2007、2009~2010年的厄尔尼诺成熟期都出现了明显的增强,但是在2004~2005年的厄尔尼诺成熟期并没有明显的增强。进一步分析发现,在2002~2003年、2006~2007年、2009~2010年的厄尔尼诺成熟期,10°N以南的热带西北太平洋区域出现了负的海面高度异常和气旋式环流异常,这主要是由热带环流区域出现的西风异常和正的Ekman抽吸通过Rossby波西传到热带西太平洋区域所致;但是在2004~2005年厄尔尼诺成熟期,海面温度异常的分布明显不同,西风异常和正的Ekman抽吸异常明显北移,导致负的海面高度异常和气旋式环流异常出现在了10°N以北的西北太平洋区域,使得北赤道流输运在2004~2005年的厄尔尼诺成熟期没有明显的增强。

In this study, we calculated the absolute geostrophic currents in the North Pacific Ocean using the P-vector method and ocean Grid Point Value of the Monthly Objective Analysis using Argo data （MOAA GPV）. We then investigated the relationship between the North Equatorial Current （NEC） transport and El Ni？o events occurring between 2001~2013. During the four El Nino events since 2001, the NEC transport significantly in-creased during the mature phases of the 2002~2003、2006~2007 and 2009~2010 El Nino events, but did not sig-nificantly increase in the mature phase of the 2004~2005 El Nino event. We performed further analyses and found that negative sea surface height and cyclonic gyre anomalies took place south of 10° N in the tropical North Pacific Ocean during the mature phases of the 2002~2003、2006~2007 and 2009~2010 El Nino events. These were mainly induced by the westerly wind anomaly and positive Ekman pumping in the tropical gyre area through west-ward-propagating Rossby waves. However, during the mature phase of the 2004~2005 El Nino event, the distribu-tion of sea surface temperature anomalies was obviously different. The westerly wind anomaly and positive Ekman pumping moved significantly northward, which led to negative sea surface height and cyclonic gyre anomalies tak-ing place north of 10° N in the northwest Pacific Ocean. As such, the NEC transport did not significantly increase during the mature phase of the 2004~2005 El Nino.