ENSO振幅不对称与赤道太平洋大气对流–海温非线性敏感性的关系研究  

Investigation of the Relationship between ENSO Amplitude Asymmetry and the Nonlinear Sensitivity of Atmospheric Convection to Sea Surface Temperature in the Equatorial Pacific

作　　者：姜明宏 谢瑞煌 

机构地区：[1]中国海洋大学海洋与大气学院海洋气象学系,山东 青岛

出　　处：《气候变化研究快报》2024年第4期802-814,共13页Climate Change Research Letters

摘　　要：ENSO (El Niño-Southern Oscillation)冷暖位相的强度存在着明显的非对称性,即El Niño强于La Niña,前人的研究将其归因于海洋非线性动力加热。本文利用再分析资料比较了ENSO发展期线性动力加热的贡献,发现El Niño发展期内赤道中东太平洋混合层海流及温跃层深度对海面异常风应力的响应要强于La Niña发展期的响应强度,这导致纬向平流反馈以及温跃层反馈均对El Niño的发展产生更大的贡献。这种海洋动力响应的不对称源自于El Niño期间热带中太平洋的异常西风响应强于La Niña时期间的异常东风响应。研究还发现热带太平洋大气对流–海温的非线性敏感性是风场对ENSO冷暖位相海温产生非对称响应的诱因,即在赤道中东太平洋25.5℃~29℃的背景海温区间,海温升高导致的大气对流加强的幅度要强于等量的海温降低引发的对流减弱的幅度,因此El Niño能激发更强的异常西风。由此,本文揭示了海气耦合的不对称性在“海温→大气对流→海面风应力→海流、温跃层→海温”这一动力链条中的传递过程,为解释ENSO振幅不对称提供了动力逻辑上的依据。El Niño-Southern Oscillation (ENSO) exhibits clear amplitude asymmetry, with El Niño being stronger than La Niña. Previous studies have attributed this to nonlinear oceanic dynamic heating. Using reanalysis data, this study compares the contributions of linear dynamic heating during the developing stages of El Niño. It is found that the responses of mixed layer currents and thermocline depth in the equatorial central-to-eastern Pacific to anomalous westerlies during El Niño is stronger than those to anomalous easterlies during La Niña, resulting in greater growth of El Niño contributed by zonal advection feedback and thermocline feedback. The asymmetric response of ocean dynamics arises from the stronger response of anomalous westerly to El Niño than the response of anomalous easterly to La Niña, which is originated from the nonlinear sensitivity of atmospheric convection to sea surface temperature (SST) in the tropical Pacific. Within the SST range of 25.5˚C~ 29˚C, the enhancement of atmospheric convection triggered by SST warming is larger than the suppression of convection generated by SST cooling of equal magnitude. El Niño can therefore drive stronger anomalous westerly winds and oceanic dynamic heating. In summary, this study reveals the transmission of the asymmetry in the air-sea coupled dynamical chain, thereby providing an interpretation on ENSO amplitude asymmetry.

关 键 词：ENSO振幅不对称 温跃层反馈 纬向平流反馈 风应力 大气对流–海温敏感性 

分 类 号：P73[天文地球—海洋科学]