Predictability of Indian Ocean Precipitation and its North Atlantic teleconnections during early Winter

Abstract

The Tropical Western-Central Indian Ocean (WCIO) precipitation anomalies play an important role in modulating the anomalous climate conditions in the northern hemisphere during the boreal early winter (November-December; ND) season. In this study, we analyzed the forcing mechanism and predictability for the early winter tropical WCIO precipitation anomalies and its teleconnections to the North Atlantic region. The two main forcing mechanisms emerging are i) Autumn Indian Ocean Dipole (IOD) and ii) a direct atmospheric teleconnection from El Niño-Southern Oscillation (ENSO). Since the autumn IOD is partially forced by ENSO, their independent contributions are also investigated. We found that the IOD contribution dominates over the ENSO contribution. The ECMWF-SEAS5 seasonal re-forecast dataset reproduces these forcing mechanisms well and shows a substantial prediction skill for the ND WCIO precipitation index. Moreover, the North Atlantic response to the positive WCIO phase projects spatially onto the positive phase of the North Atlantic Oscillation (NAO) through atmospheric teleconnections and leads to warming in the central and western European region. This teleconnection is reproduced by ECMWF-SEAS5, but with weaker amplitude. Moreover, a substantial prediction skill for the NAO as well as for the central and western European temperature anomalies is noted, which is mostly induced by the Indian Ocean precipitation anomalies during early winter.

The role of storm‐track dynamics in the intraseasonal variability of the winter ENSO teleconnection to the North Atlantic

“…Whilst most of the literature has focused on the ENSO teleconnection to the North Atlantic in the late winter, recent studies have emphasised the intraseasonal variability of the teleconnection. In the early winter (November–December), the teleconnection is quite different from that in the late winter, with the associated sea‐level pressure anomalies closely resembling the “East Atlantic” pattern (EA) rather than the NAO (Ayarzagüena et al, 2018; Geng et al, 2023; King et al, 2018; King et al, 2023; Moron & Gouirand, 2003), as also shown here in Figure 1a; in addition, some studies have highlighted the possible role of the tropical Indian Ocean in modifying the ENSO teleconnection to the North Atlantic in early winter (Abid et al, 2021, 2023). Previous studies have demonstrated that free‐running coupled climate models struggle to reproduce the early‐season teleconnection to the North Atlantic (Ayarzagüena et al, 2018; Molteni, 2020).…”

Winter precipitation predictability in Central Southwest Asia and its representation in seasonal forecast systems

“…Recent studies suggest that October IOD and contemporaneous ENSO can affect precipitation variability in the western Indian Ocean during early winter. 43 To understand this phenomenon more deeply, we analyze the association of bi-monthly IOPD with the October preconditioning of IOD and ENSO. In October, ENSO and IOD are strongly correlated (ERA5=0.67; MERRA2=0.62).…”

“…As the winter progresses, precipitation in the western Indian Ocean weakens (Figure S12), which correlates more with IOD. 43 Hence, IOD loses its influence over IOPD. On the other hand, ENSO strongly correlates with IOPD and eastern IO precipitation.…”

Comparative Analysis for Atmospheric Oscillations

“…Atmospheric oscillations may lead to zonal atmospheric variations and climatic conditions [36][37][38][39][40][41][42][43][44][45][46][47][48][49][50][51]. For example Arctic Oscillation led to precipitation increment [52].…”