摘要
[目的]研究赤道东太平洋热带不稳定波(tropical instability waves,TIWs)的时空分布特征及其驱动机制.[方法]利用数据插值经验正交函数方法对MODIS卫星2003-2018年赤道东太平洋海表面温度(sea surface temperature,SST)数据进行重构,进而提取TIWs的波长和速度,并分析其时空分布特征以及与赤道风场和流场的关系.[结果]研究发现:TIWs在纬向上呈正负相位交替分布,在经向上则表现为双峰结构.季节性方面,TIWs在3-5月强度最弱,而在8-10月强度最强.纬向风场通过影响赤道纬向流场,特别是南赤道流(South Equatorial Current,SEC)的北分支(SEC-N)和北赤道逆流(North Equatorial Countercurrent,NECC)的剪切调控TIWs的生成;经向风场则通过调制“冷舌”边缘的SST梯度影响TIWs的生成.在年际尺度上,TIWs在厄尔尼诺(El Nino)年受到抑制,在拉尼娜(La Nina)年得到加强.纬向风场、纬向流场和TIWs三者的异常均超前于厄尔尼诺-南方涛动(El Nino-Southern Oscillation,ENSO)指数所刻画的赤道东太平洋SST异常,这表明纬向风场影响下的纬向流场剪切同样驱动TIWs的年际变化.NECC上空纬向风异常较弱,而SEC-N上空纬向风异常较强,这使得SEC-N年际变化主导流场剪切的强度,对TIWs的年际特征有重要作用.[结论]这一发现强调了大气风场和海洋动力过程共同驱动TIWs的季节性特征和年际变化.
[Objective]Tropical instability waves(TIWs)are seasonal undulations that meander westward along the thermal fronts within the Eastern Equatorial Pacific region,exhibiting significant spatiotemporal variations.This study aims to address the cloud contamination issues caused by high cloudiness and rainfall in tropical regions that limit the effectiveness of satellite remote sensing technologies.The goals are to enhance the capture of detailed TIWs characteristics,increase the application value of satellite data in TIWs research,and deepen the understanding of the characteristics and seasonal variability of TIWs.Moreover,the study seeks to elucidate the significance of ocean-atmosphere interactions in the formation process of TIWs.[Methods]This study reconstructed the sea surface temperature(SST)data from the moderate-resolution imaging spectroradio-meter(MODIS)satellite for the equatorial Pacific spanning from 2003 to 2018 using the data interpolating empirical orthogonal functions(DINEOF)approach.Utilizing the reconstructed satellite data,the study applied the Radon transform method to accurately extract the wavelengths and velocities of TIWs from the Hovm ller diagrams of filtered SST,thereby precisely delineating and analyzing the spatiotemporal distribution characteristics of TIWs.In conjunction with wind and current field data from the Equatorial Pacific,the study explored the significant role of large-scale ocean-atmosphere interactions in the genesis process of TIWs.[Results]Findings of this study suggest that the wavelengths and velocities of TIWs obtained via the Radon method can accurately characterize the seasonal and interannual features of TIWs,both serving as important indicators of TIWs intensity.The spatial characteristics of TIWs are significant,exhibiting an alternating distribution of positive and negative phases in the zonal direction and a bimodal structure in the meridional direction.Seasonally,TIWs are weakest from March to May and strongest from August to October.The seasonality of TIWs is closely related to the variations in the meridional and zonal wind fields associated with the seasonal migration of the intertropical convergence zone(ITCZ).Zonal wind fields influence the generation of TIWs primarily through modulating the shear of the equatorial zonal current field,especially the northern branch of the South Equatorial Current(SEC-N)and the North Equatorial Counter Current(NECC).Meridional wind fields significantly impact the generation of TIWs by modulating the SST gradient at the edge of the"cold tongue".Considering the interannual variability,TIWs are suppressed during El Nino years and enhanced during La Ni a years.The anomalies in zonal wind fields,zonal current fields,and TIWs precede the SST anomalies in the Eastern Pacific as revealed by the ENSO index,indicating that the shear in the zonal current field driven by zonal wind fields also drives the interannual signal of TIWs.Anomalous zonal wind fields in the Equatorial Pacific induced by ENSO,and the variability of the zonal wind field caused by abnormal movements of the ITCZ,counteract each other over the NECC while reinforcing in the same direction over the SEC-N.These results in the interannual variability of SEC-N dominating the intensity of the flow field shear,which plays a significant role in the interannual characteristics of TIWs.[Conclusions]The reconstructed satellite data successfully delineated the significant spatiotemporal distribution characteristics of TIWs,present on both the northern and southern sides of the Equatorial Pacific,with pronounced seasonal and interannual variations.The atmospheric wind fields and oceanic dynamic processes jointly drive the seasonal and interannual variability of TIWs.Both zonal and meridional wind fields play a crucial role in the formation of the seasonal characteristics of TIWs.The interannual anomalies of the zonal wind field and the resultant anomalies in the zonal current field,particularly those of the SEC-N,dominate the interannual characteristics of TIWs.These findings advance the scientific understanding of the significant role of large-scale ocean-atmosphere interactions in the genesis of TIWs and offer valuable insights for the construction of future climate prediction models.
作者
高志斌
王云涛
柴扉
GAO Zhibin;WANG Yuntao;CHAI Fei(School of Oceanography,Shanghai Jiaotong University,Shanghai 200240,China;State Key Laboratory of Satellite Ocean Environment Dynamics,Second Institute of Oceanography,Ministry of Natural Resources,Hangzhou 310012,China;College of Ocean and Earth Sciences,Xiamen University,Xiamen 361102,China)
出处
《厦门大学学报（自然科学版）》
CAS
CSCD
北大核心
2024年第3期512-525,共14页
Journal of Xiamen University：Natural Science
基金
国家自然科学基金(42176013)。
关键词
赤道东太平洋
海表面温度
热带不稳定波
厄尔尼诺-南方涛动
Eastern Equatorial Pacific
sea surface temperature
tropical instability wave
El Nino-Southern Oscillation
