热带太平洋淡水通量年际变率对ENSO的作用机制及数值模拟研究  

MODELING ON THE EFFECTS ON ENSO DUE TO INTERANNUAL VARIABILITY OF FRESHWATER FLUXES IN THE TROPICAL PACIFIC

作　　者：尹露莹 张荣华 智海[2] YIN Lu-Ying;ZHANG Rong-Hua;ZHI Hai(School of Marine Sciences,Nanjing University of Information Science and Technology,Nanjing 210044,China;College of Atmospheric Sciences,Nanjing University of Information Science and Technology,Nanjing 210044,China;Laoshan Laboratory,Qingdao 266237,China)

机构地区：[1]南京信息工程大学海洋科学学院,江苏南京210044 [2]南京信息工程大学大气科学学院,江苏南京210044 [3]崂山实验室,山东青岛266237

出　　处：《海洋与湖沼》2024年第6期1350-1367,共18页Oceanologia Et Limnologia Sinica

基　　金：崂山实验室科技创新项目,LSKJ202202403号;国家自然科学基金项目,42030410号;内蒙古自治区气象局引导性创新基金项目,nmqxydcx202221号。

摘　　要：海气界面间淡水通量(freshwater flux, FWF;定义为降水减蒸发)是热带太平洋气候系统中对海洋有重要作用的大气强迫之一,与风应力和热通量共同影响厄尔尼诺-南方涛动(El Nino-Southern Oscillation, ENSO)。尽管这些大气强迫场共同作用于海洋,但FWF在其中的单独强迫作用及相关过程和机制仍需深入探究。本文通过海洋环流模式(ocean general circulation model, OGCM)进行模拟,进一步使用温度和盐度收支分析以及区分温盐相对贡献的诊断分析方法,量化热带太平洋FWF年际变率对上层海洋的净作用。结果表明,在El Nino事件发生时,FWF正异常强迫直接导致赤道太平洋中部海表盐度(sea surface salinity, SSS)降低,同时增强上层海洋层结稳定度。此外,FWF正异常强迫还会导致赤道太平洋中部浮力通量(buoyancy flux, BF)增加,从而减弱了次表层的混合和夹卷作用,使局地的混合层变浅。从气候效应来看,由FWF年际变率引起的海洋过程有助于赤道东太平洋海表温度(sea surface temperature, SST)暖异常的维持和增强。通过定量分析表明,SSS变化与FWF强迫强度密切相关,赤道太平洋中部FWF异常每增加1.0 mm/d会使得SSS异常降低约0.02,并且使得赤道太平洋东部SST异常升高约0.12℃,在增温过程中垂直混合和夹卷作用是主导的贡献项。以1997~1998年的El Nino事件为例,FWF正异常引起的SST暖异常增量占总异常的11.8%。本文所揭示的FWF强迫场对ENSO的单独作用有助于完善我们对整个热带太平洋海气耦合系统的认知,为进一步改进ENSO的过程表征和预测提供科学指导。Freshwater flux(FWF;defined as precipitation minus evaporation)at the air-sea interface is one of the important atmospheric forcings to the ocean in the tropical Pacific climate system,additional to wind stress and heat flux that influence the El Niño-Southern Oscillation(ENSO).Although these atmospheric forcing fields act together on the ocean,the individual forcing role of FWF and the related processes and mechanisms still need to be deeply explored.We examined the net effect of FWF interannual variability on the upper ocean by using an ocean general circulation model(OGCM)and further quantified them using heat and salt budget analyses as well as diagnostic analyses that distinguish between the relative contributions of temperature and salinity.Results indicate that during El Niño events,the FWF positive anomaly forcing directly leads to a decrease in sea surface salinity(SSS)in the central equatorial Pacific and enhances the stability of the upper ocean stratification.Furthermore,the FWF positive anomaly forcing also increases buoyancy flux(BF)in the central equatorial Pacific,which reduces vertical mixing and entrainment processes,resulting in a local shoaling of the mixed layer.In terms of climate effects,the oceanic processes induced by the interannual FWF variability contribute to the maintenance and enhancement of sea surface temperature(SST)warm anomalies in the eastern equatorial Pacific,with vertical mixing and entrainment being the dominant contributing terms in the warming process.Quantitative analysis showed that SSS changes are closely related to the forcing intensity of the FWF,with an increase in FWF anomalies in the central equatorial Pacific by 1.0 mm/d corresponding to a decrease in SSS by about 0.02 and to an increase in SST in the eastern equatorial Pacific by about 0.12℃.In the case of the 1997~1998 El Niño event,for example,the incremental SST warm anomalies due to positive FWF effects contribute 11.8%of the total SST anomalies.The separate role of the FWF forcing field in ENSO reveal

关 键 词：海气界面淡水通量 ENSO 海表盐度和温度 热带太平洋 分层型海洋模式 热盐收支分析 温盐相对贡献 

分 类 号：P731[天文地球—海洋科学]