2016与1998年春季北大西洋海表温度异常的差异及成因

doi:10.11978/2019085

摘要/Abstract

摘要：

利用再分析资料以及混合层海温诊断方程, 研究1997—1998与2015—2016年超级厄尔尼诺次年北大西洋海表温度异常(sea surface temperature anomalies, SSTA)的差异及成因。结果显示, 北大西洋SSTA在1998年春季呈明显正负正三极型式分布, 而在2016年呈弱的负正负型态。诊断热带北大西洋SSTA的影响因素表明, 1998年春季暖SSTA除了之前研究强调的海洋表面向大气的潜热输送异常减少, 以及吸收太阳辐射的增加外, 海洋动力过程即Ekman纬向漂流也起着重要的作用。热力过程与厄尔尼诺峰值后出现的北大西洋涛动(North Atlantic Oscillation, NAO)负位相有关, 其可引起亚速尔高压减弱, 产生西南风异常, 通过风-蒸发-海表温度(sea surface temperature, SST)反馈机制使热带北大西洋蒸发减弱, 海表增暖, 沃克环流下沉支的东移对这一增暖也有贡献。与1997—1998厄尔尼诺事件不同, 2015—2016厄尔尼诺事件没有强迫出负位相NAO, 而是出现弱NAO正位相, 热带北大西洋为弱的东风异常, 使海表发生一定的冷却, 形成2016春季北大西洋SSTA与1998年的明显差异。

关键词: 北大西洋海表温度异常, 厄尔尼诺衰减位相, 大气遥响应, NAO位相

Abstract:

In this paper, we use reanalysis data and mixed layer temperature (MLT) budget analysis to study the differences of the North Atlantic sea surface temperature anomalies (SSTAs) between two Super El Ni?o (1997-1998 and 2015-2016) events and the causes for the differences. The results show that in the spring of 1998 the North Atlantic SSTA had clear positive, negative and positive distribution, while in spring 2016 it presented weakly negative, positive and negative distribution. The diagnostic results of factors influencing the SSTA in the tropical North Atlantic indicate that in the spring of 1998, in addition to the reduction of latent heat transferring from ocean surface to atmosphere and the increase in solar radiation absorption, the marine dynamic process, i.e., zonal Ekman drift, also played an important role. The thermal process was related to the negative phase of the North Atlantic Oscillation (NAO) that occurred after the peak of El Ni?o, which caused the Azores high pressure to weaken and generated southwesterly wind anomaly. The evaporation of the tropical North Atlantic was attenuated by the wind-evaporation-SST feedback mechanism. The eastward shift of the Walker circulation sinking branch also contributed to this warming. Different from the 1997-1998 El Ni?o event, the 2015-2016 El Ni?o event caused a weakly positive NAO phase instead of a negative one. The weak easterly anomaly in the tropical North Atlantic caused SST cooling; this may be the main reason for the significant difference between the North Atlantic SSTAs in the springs of 1998 and 2016.

Key words: North Atlantic SSTA, El Ni?o decay phase;, atmospheric teleconnection, NAO phase

薛文璟, 余锦华, 陈林. 2016与1998年春季北大西洋海表温度异常的差异及成因[J]. 热带海洋学报, 2020, 39(3): 19-30.

Wenjing XUE, Jinhua YU, Lin CHEN. Differences of sea surface temperature anomalies in the North Atlantic in springs of 1998 and 2016 and their causes[J]. Journal of Tropical Oceanography, 2020, 39(3): 19-30.

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