The role of Pacific subtropical high belts in the ENSO cycle

Abstract

This article conducted statistical analyses on the formation of El Niño and Southern Oscillation (ENSO) from several angles by using conventional data. We found that both El Niño and La Niña are closely associated with the preliminary activity of the Pacific subtropical high (PSH) belts on both sides of the equator if bringing an assumption of the influence of annual cycle on ENSO cycle into our calculations. The PSH belts, especially in their eastern sides, tended to have been continuous weakening for months before El Niño maturing. Oppositely, the continuous enhancing of the PSH belts might be regarded as a prelude of a La Niña. This signal the PSH belts send to omen ENSO's coming appeared about two months earlier than the one from the elements in tropical regions. We found that the strengthening or weakening of the PSH belts could act as a more original force for driving the ENSO cycle than the elements in tropics through controlling the variation of trade winds. Since the southern PSH belt appeared more powerful than the northern one in the situation, the phase lock of the ENSO cycle might be explained by this clue. Because the southern PSH belt that approaches the nearest area of the equator every June-August in a calendar year can exert a more powerful impact on equatorial elements, SST in Eastern Equatorial Pacific will be significantly affected 3-4 months later, i.e. the general ENSO mature phase happening around the end of a calendar year. We proposed a plausible mechanism for the ENSO formation based on the results and conducted a targeted discussion on this new mechanism that could explain the problems the current conceptual ENSO models left.

The Anomalous Regional Hadley Circulation in the ENSO Cycle

“…What Bjerknes (1969) mentioned about the El Niño-enhanced Hadley circulation could involve either the former or the latter. However, the former does not guarantee to make a significant change in the strength of eastern PSH that is crucial to affect SST in the Eastern equatorial Pacific (EEP) as a necessary condition for the formation of ENSO conversion (Wang 2019). Note that the PSH strength we mentioned here only means the one reflected on the SLP with a regional variation.…”

“…However, the conceptual models have apparent shortcomings, especially ignoring a vital impact on ENSO over extratropical regions (White et al 2002;Vimont et al 2003;Anderson 2004;Wang et al 2013;Ludescher et al 2013;Tasambay-Salazar et al 2015). Wang (2019) established a relatively complete ENSO theory based on analyzing and calculating many observational data to avoid these problems. The new theory pointed out that the force that drives the ENSO cycle is not confined to the tropical region as previously thought but more primitively in the far away atmospheric circulation system, i.e., the eastern Pacific Subtropical High (PSH) Belts.…”

“…Thus, this study will explore how the ENSO through the Hadley cell can affect the PSH, causing an inverse response to reduce previously equatorial thermal intensity. Undoubtedly, understanding this mechanism is greatly helpful to the improvement of the new ENSO theory proposed by Wang (2019).…”

Southwest Pacific Paleoceanography During the Late Holocene: 3000 years of ocean circulation and marine biogeochemistry reconstructed from New Zealand deep-sea black corals

“…A southward migration of the SPA weakens the southeast trade winds, enhances the equatorial countercurrent (ECC) and allows for a southward intrusion of the northeast trade winds in the equatorial Pacific (see Fig. 1 in Zou et al, 2018;Y. Wang, 2019).…”

“…An enhanced ECC leads to an anomalous accumulation of warm water in the central-eastern equatorial pacific brought by a reversal of the Walker circulation. Therefore, the migration of the SPA is a driver in ENSO variability and so the major climate features that drive SPG circulation (SPA, Hadley and Walker circulation) also relate to ENSO variability (Zou et al, 2018;Y. Wang, 2019).…”