Origins of Biweekly Sea Surface Temperature Variability in the Eastern Equatorial Pacific and Atlantic

Biweekly sea surface temperature (SST) variability significantly contributes to over 50% of the intraseasonal variability in the eastern equatorial Pacific (EEP) and Atlantic (EEA). Our study investigates this biweekly variability, employing a blend of in-situ and reanalysis data sets. The research identifies biweekly signals in SST, meridional wind, and ocean currents, notably in September-November in EEP and June-August in EEA. Biweekly southerly (northerly) winds drive instantaneous northward (southward) ocean currents in EEP, but with a 1-2-day phase delay in EEA. Consequently, these currents lead to SST anomalies with a 3-4-day lag in both EEP and EEA due to the presence of the cold tongue. The study reveals the origin of biweekly wind fluctuations in the western Pacific for EEP and the subpolar Pacific for EEA, connected by atmospheric Rossby waves validated through a linearized non-divergent barotropic model. This research affirms the influence of subtropical and subpolar atmospheric forcing on equatorial SST. Our research focuses on understanding the regular changes in sea surface temperature (SST) occurring every 2 weeks, which significantly contribute to the seasonal variations in the eastern equatorial Pacific (EEP) and Atlantic (EEA). By analyzing a mix of direct and reconstructed data, we uncover the distinct patterns of these biweekly changes in SST, winds, and ocean currents. Our investigation shows that the movements of the ocean currents are closely linked to the shifts in wind direction, affecting the temperature of the ocean waters. Notably, we observe a delay in the relationship between wind and SST in both EEP and EEA. Through our analysis, we establish that the origins of these biweekly wind patterns can be traced to specific regions in the Pacific. Moreover, we identify the role of atmospheric Rossby waves in connecting these wind patterns to their source regions, which helps us understand how changes in atmospheric conditions in different parts of the ocean can impact the equatorial SST. Over 50% of intraseasonal SST variability in the eastern equatorial Pacific and Atlantic is attributed to biweekly fluctuations The atmospheric winds play a crucial role in driving the biweekly SST variability Biweekly winds in the eastern equatorial Pacific and Atlantic stem from the subtropical and subpolar regions, respectively