Abstract
Due to the profound impact of El Niño-Southern Oscillation (ENSO) on global climate and weather, extensive research has been devoted to its prediction. However, prediction accuracy based on observation is still insufficient and largely limited to less than one year of lead time. In this study, we demonstrate the possibility that anomalous sea surface temperature (SST) warming (cooling) in the Western Hemisphere Warm Pool (WHWP, a.k.a. Atlantic Warm Pool) near the Intra-Americas Sea (IAS), which is the second largest warm pool on the planet, contributes to the initiation of La Niña (El Niño) with a 17-month lag time. SST anomalies in WHWP in late boreal summer contribute significantly to the emergence of the Pacific meridional mode (PMM) via interaction between the ocean and atmosphere over the subtropical North Pacific during the subsequent winter and spring. Near-equatorial surface wind anomalies associated with the PMM can further trigger ENSO through the dynamics of the equatorial oceanic waves. Thus, this observational analysis presents a clear step-by-step explanation about the influence of WHWP on ENSO development with a 17-month lead time.
Highlights
Atmospheric teleconnection from other oceans may help to trigger El Niño
By analyzing observational and model simulation data, we showed a significant influence of WHWP on El Niño with a 17-month lead time
Results of our evaluation indicated an increase of an SST anomaly (SSTA) in the WHWP in mid-summer to early-fall induces a northerly wind anomaly over the North Pacific as a result of Rossby wave propagation, which in turn generates a cold SSTA and a high SLP anomaly (SLPA) in the subtropical northeastern Pacific
Summary
Atmospheric teleconnection from other oceans may help to trigger El Niño. For example, Atlantic Niño, which peaks in summer, may independently enhance El Niño development by modulating the Walker Circulation in the Atlantic and eastern Pacific sector[19,20,21]. It was emphasized that the effect of IOD could help predict El Niño events with a 13 to 15-month lead time These results imply that interbasin interaction can play a key role in El Niño prediction beyond one year. Some forecast experiments have shown that the interbasin interactions with the Indian and Atlantic Oceans can improve ENSO prediction[25] These observational and modeling studies motivated us to consider other possible precursors in the Atlantic Ocean that could extend El Niño prediction lead time. In this light, we suggest that an SSTA in the Western Hemisphere Warm Pool[26] (WHWP, a.k.a. Atlantic Warm Pool), which is located in the Intra-Americas Sea (IAS), is a new independent precursor of El Niño with a forecast lead time of 17 months
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