南太平洋Stokes漂流在厄尔尼诺衰退过程中的降温作用

Cooling Effect of the Stokes Drift in the South Pacific During El Nino’s Decline

赤道东太平洋海表面温度的变化在全球气候变化中扮演着重要的角色,波浪是影响海表面温度的重要因素。为了进一步研究波浪对全球气候的影响,利用ECMWF(European Centre for Medium-Range Weather Forecasts)发布的波浪参数、海表面温度(Sea Surface Temperature,SST)等再分析数据,采用EOF(Empirical Orthogonal Function)分析和超前滞后相关分析等方法,分析了南太平洋涌浪区Stokes漂流与厄尔尼诺事件的关系。首先选用一种涌浪指标和多个涌浪特征值总结了全球的涌浪特征,得到涌浪在低纬、南半球和大洋东边界更占优的结论,并由此划定南太平洋涌浪区,发现了其连接南大洋和赤道东太平洋的通道作用。进而研究了南太平洋涌浪区Stokes漂流对赤道东太平洋SST的影响,结果显示:在厄尔尼诺事件发生后,该区域的经向Stokes漂流会产生强化,波浪诱导的Stokes漂流会将高纬冷水输送到低纬海域,使得低纬海域降温,加速厄尔尼诺事件的衰退,进而影响到全球气候。本文为解释厄尔尼诺的衰退提供了新的思路,也为波浪的大尺度效应研究开辟了新的方向。

The variation of sea surface temperature(SST)in the equatorial eastern Pacific plays an important role in global climate change,and waves are an important factor affecting sea surface temperature.In order to further study the impact of waves on the global climate,the relationship between Stokes drift in the South Pacific swell region and El Nino is analyzed by using the reanalysis data of wave parameters and sea surface temperature published by ECMWF,the methods of EOF analysis,and advanced-lag correlation analysis.First,a swell index and various wave characteristic values are selected to summarize the characteristics of global swell.It is concluded that the swell is more dominant in low latitudes,southern hemisphere,and the eastern boundary of the ocean.Based on this,the swell region of the South Pacific is delineated,and its role as a channel connecting the Southern Ocean and the equatorial eastern Pacific is found.Furthermore,the influence of Stokes drift in the South Pacific swell region on the SST in the equatorial eastern Pacific is studied.The results show that following the occurrence of El Nino event,the meridional Stokes drift in the region will be strengthened,so the wave induced Stokes drift transports the high latitude cold water to low latitude sea area,thus cools the low latitude sea area and accelerates the decline of El Nino,affecting the global climate.This paper not only provides a new idea of explaining the decline of El Nino,but also opens up a new direction for the study of large-scale effects of waves.