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CN 11-1768/O4

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热带太平洋盐度年际变化对海表温度异常作用比较:1997/1998,2014/2015 和2015/2016 El Ni?o事件
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1.南京信息工程大学气象灾害教育部重点实验室/气候与环境变化国际合作联合实验室/气象灾害预报预警与评估协同创新中心,江苏 南京;2.南京信息工程大学气象灾害教育部重点实验室/气候与环境变化国际合作联合实验室/气象灾害预报预警与评估协同创新中心,江苏 南京 210044;3.中国科学院大气物理研究所LASG,北京

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国家重点基础研究规划项目,国家自然科学基金


Contrasting Salinity Interannual Variability in the Tropical Pacific and Its Effects on Recent El Ni?o Events: 1997/1998, 2014/2015, 2015/2016
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Affiliation:

1.College of Atmospheric Sciences, Nanjing University of Information Science and Technology, Nanjing,China;2.State Key Laboratory of Numerical Modeling for Atmospheric Sciences and Geophysical Fluid Dynamics (LASG), Institute of Atmospheric Physics (IAP), Chinese Academy of Sciences, Beijing, China;3.College of Atmospheric Sciences, Nanjing University of Information Science and Technology, Nanjing, 210044, China

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    摘要:

    海洋盐度变化为研究气候变化的机制提供了一个新的视角。本文通过对比1997/1998、2015/2016两次强厄尔尼诺 (El Ni?o) 事件和2014/2015特殊El Ni?o事件,对盐度变化及其影响海表面温度异常 (SSTA) 的物理过程进行了比较分析。研究表明,El Ni?o和南方涛动 (ENSO) 发展的强弱与热带西太平洋大范围海表层盐度异常 (SSSA) 出现并向东扩散的差异有明显关联。1997-1998、2015-2016年赤道东太平洋地区SSTA的增暖,对应两次强ENSO事件,在发生年的4月,中西太平洋海域出现了明显的负SSSA,之后东移至日期变更线以西,SSSA引发的混合层深度 (MLD) 变浅、障碍层厚度 (BLT) 变厚,导致热带中-西太平洋表层的升温增强,促使了赤道中太平洋的早期变暖;2014/2015弱ENSO事件虽然在发生年4月位于赤道中西太平洋出现了负SSSA,但没有发展东移,导致BLT的加厚过程减弱,对表层温度的调制作用减弱甚至消失。三次ENSO事件对应的盐度变化过程中,水平平流及淡水通量 (FWF) 引起的外强迫是影响盐度收支的主要因子,水平平流影响盐度异常的前期变化,触发事件的发生;位于热带太平洋西部的降水引起的FWF负异常的影响最为显著,对ENSO异常信号出现后SSSA的维持起决定性作用。相比较两次强ENSO事件,2014/2015 El Ni?o对应的早期FWF负异常没有发展和东移且之后迅速减弱,导致中西太平洋盐度负趋势减缓,MLD加深,BLT变薄,促使上表层海水冷却,抑制了赤道东太平洋的早期变暖和El Ni?o发展。 研究结果表明,盐度变化与ENSO密切相关,热带中西太平洋海域早期表层盐度变化可能可以作为SSTA的指数。特别地,SSSA在调节海洋的SSTA时,不仅影响它的强度,而且可以作为判断ENSO发展和强弱的前兆因子。

    Abstract:

    Ocean salinity variation provides a new insight into related ENSO expressed by climate variability. In this study, the comparisons of salinity variability and its related dynamical processes responsible for SSTA have been extensively described and analyzed among two strong ENSO, 1997/1998, 2015/2016 and one special ENSO, 2014/2015. The study shows that the development of ENSO is significantly associated with the occurrence and eastward diffusion of large-scale surface salinity anomaly (SSSA) in the western-tropical Pacific. In April of 1997 and 2015 corresponding to two strong ENSO events, there was a significant negative SSSA in the western-central Pacific, and then it moved eastward to the west of the dateline which induced the mixing layer depth (MLD) shallow, and the barrier layer thickness (BLT) thickened, which enhanced the surface warming in the tropical central Pacific and the early warming in the equatorial eastern-central Pacific. Although negative SSSA occurred in April of 2014/2015 weak event in the equatorial western-central Pacific, it did not develop eastward, resulting in weakened thickening process of BLT and weak modulation effect on surface temperature. For salinity change process corresponding to three ENSO events, surface advection and surface forcing caused by fresh water flux (FWF) were the major contributors to salinity budget. Surface advection influenced the former variability of salinity tendency, inducing the occurrence of ENSO signal. The precipitation in the tropical western Pacific played the most significant negative influence on FWF, which made a decisive role in the occurrence of SSSA and in the development of ENSO. Compared with the two strong ENSO events, the early FWF negative anomaly in 2014/2015 did not develop and moved eastward and weakened rapidly, resulting in a slowing of the negative salinity tendency in the western-central Pacific, deepening of MLD, thinning of BLT, and rapid cooling of the surface layer, which inhibited the early warming in the equatorial-eastern Pacific. The results of study demonstrate that the salinity change is closely related to ENSO, and early SSS in the tropical western-central Pacific could be used as the index of SSTA. In particular, SSSA not only affects the strength of ocean SSTA, but also could be used as a precursor to judge the development and strength of ENSO.

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  • 收稿日期:2019-06-13
  • 最后修改日期:2019-10-26
  • 录用日期:2020-01-02
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