Character analysis of tropical instability waves based on reconstructed satellite observations of sea surface temperature
[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 Hovmoller 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 Nina 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.
万方数据
维普
