The Unique Role of the Intraseasonal Zonal Wind in March Over the Equatorial Western Pacific Contributes to Shaping the Subsequent ENSO Development

• Published in: Geophysical research letters 2024-12, Vol.51 (23), p.n/a
• Main Authors: Cao, Ting‐Wei, Zheng, Fei, Yu, Jin‐Yi, Fang, Xiang‐Hui, Zhong, Wen‐Xiu
• Format: Article
• Language: English
• Subjects: air‐sea interaction; Calendars; Climate; Climate models; Climate prediction; Convective activity; eastward‐propagating MJO activity; El Nino; El Nino phenomena; El Nino-Southern Oscillation event; El Niño‐Southern Oscillation development; Global climate; Impact analysis; Impact prediction; Information processing; Interdecadal variability; intraseasonal zonal wind; Madden-Julian oscillation; Ranking; Sea surface temperature; Southern Oscillation; Spring; Spring (season); Surface temperature; Variability; Wind; Winds; Zonal winds
• ISSN: 0094-8276; 1944-8007
• DOI: 10.1029/2024GL110976

The predictability of the El Niño‐Southern Oscillation (ENSO) is significantly limited by the spring predictability barrier (SPB). Our observational analysis suggests that considering high‐frequency wind components during the spring season may mitigate the SPB impact on ENSO predictability. The intraseasonal zonal wind in March over the equatorial western Pacific initially perturbs the sea surface temperature (SST). It contributes nearly 40% of the east‐west SST gradient after 2–3 months, ranking first among other calendar months. This significant contribution causes March to become the earliest month to effectively indicate the following ENSO direction due to the active eastward‐propagating Madden‐Julian oscillation (MJO) activity. Through the obvious variation of the eastward‐propagating MJO speed, it also shows the possible close relationship between the mean SST state and the interdecadal variability in intraseasonal zonal wind. Additionally, the current strong variability of intraseasonal zonal wind suggests the important role of atmospheric information in recent ENSO development. Plain Language Summary The El Niño‐Southern Oscillation (ENSO) is known to have a far‐reaching impact on global climate. Our present climate models, however, remain large challenges in predicting ENSO events when the predictions made cross the boreal spring. In this study, we find that utilizing the atmospheric information in spring could weaken the challenges mentioned above. The intraseasonal zonal wind with a main period of 30–90 days over the equatorial western Pacific in March provides strong support for the ENSO developments after 2–3 months, with a contribution as high as nearly 40%, ranking first among other calendar months. This significant contribution establishes a strong connection between the ENSO peak states and the high‐frequency winds, and it causes March to become the earliest month to effectively indicate the following ENSO developments. Changes in long‐term mean sea surface temperature modulate the eastward propagation speed of convective activity, and it possibly establishes significant relationship with the intraseasonal zonal wind in March. Recently, the strong intraseasonal zonal wind has alerted us to focus on the high‐frequency winds in spring and their controlled processes, which could improve our prediction skills across the spring season. This study highlights the potential impact of intraseasonal zonal winds in March on ENSO's predictability as a