Pacific meridional mode and El Niño—Southern Oscillation

Abstract

[1] We present intriguing evidence that the majority of El Niño events over the past four decades are preceded by a distinctive sea-surface warming and southwesterly wind anomaly in the vicinity of the Intertropical Convergence Zone (ITCZ) during the boreal spring. This phenomenon, known as the Meridional Mode (MM), is shown to be intrinsic to the thermodynamic coupling between the atmosphere and ocean. The MM effectively acts as a conduit through which the extratropical atmosphere influences ENSO. Modeling results further suggest that the MM plays a vital role in the seasonal phase-locking behavior of ENSO. The findings provide a new perspective for understanding the important role of thermodynamic ocean-atmosphere feedback in ENSO and may have profound implications for ENSO prediction, particularly the unresolved issue of the spring predictability barrier.

Linear trends in sea surface temperature of the tropical Pacific Ocean and implications for the El Niño-Southern Oscillation

“…The westernmost central Pacific SST anomaly broadly extends northeastwards into the Northern Hemisphere subtropics (to *30°N). This third SST pattern is also reminiscent of the so-called Pacific Meridional Mode, which may precede ENSO events (Vimont et al 2003;Chang et al 2007;Zhang et al 2009). The PC-3 monthly time series reveals no discernible linear trend in contrast to PC-1 and PC-2 (Fig.…”

Probable causes of the abnormal ridge accompanying the 2013–2014 California drought: ENSO precursor and anthropogenic warming footprint

“…The SST footprint then lasts into the following summer in the subtropics and potentially impacts equatorial zonal wind stress [Anderson, 2003;Vimont et al, 2001Vimont et al, , 2003. Under the SFM framework, two precursor patterns are prominent: The Pacific Meridional Mode based upon wind and SST anomalies in the eastern half of the North Pacific [Chang et al, 2007;Chiang and Vimont, 2004], and the Western North Pacific (WNP) pattern located in the western part of the basin [Wang et al, 2012[Wang et al, , 2013. Given the results from Figures 1d and 3, it is likely that the SST and wind anomalies of the WNP are able to produce a specific teleconnection that contributes to the dipole's formation.…”

Simulating the Role of Subtropical Stratocumulus Clouds in Driving Pacific Climate Variability

“…Several other studies have then suggested that there is a positive feedback among subtropical low-level clouds, SST, and large-scale atmospheric circulation in the tropical Pacific (Philander et al 1996;Nigam 1997;Norris 2005;Clement et al 2009). The SST anomalies propagate from the subtropical NE and SE Pacific regions to the equatorial Pacific via the atmospheric wind-evaporation-SST (WES) feedback (Zhou and Carton 1998) and influence ENSO and the tropical Pacific climate (Chang et al 2007;Matei et al 2008;Okumura (2013); Zhang et al 2014). Cloud feedback in the subtropical stratocumulus regions could therefore lead to decadal anomalies in SST throughout the Pacific basin (cf.…”