Predictability of the North Atlantic European region and the role of Indian Ocean during early winter

Abstract

<p>The North Atlantic European (NAE) regional circulation anomalies variability and predictability during the boreal winter season is modulated through both stratospheric and tropospheric pathways on sub-seasonal to seasonal timescales. El Niño-Southern Oscillation (ENSO) through the atmospheric teleconnections is one of the dominating forcing that modulates the global climate variability and Predictability during the boreal winter season. However, recent studies indicate the intra-seasonality in the ENSO teleconnections, where through the inter-basin interactions the Indian Ocean (IO) bridges the ENSO response to the NAE region in the early winter, while the direct ENSO response dominates in latter half of the boreal winter. Therefore, in the current study we analyzed the predictability of the NAE circulation anomalies and the tropical Indian Ocean precipitation anomalies during the early winter season using the ECMWF System-5 seasonal (SEAS5) dataset. We noted the boreal Autumn Indian Ocean Dipole (IOD) conditions are the pre-courser for the early winter precipitation anomalies in the Tropical Western-Central Indian Ocean (TWCIO) region, which dominates the ENSO response to the IO precipitation anomalies during the earlier half of the winter season. These TWCIO precipitation anomalies are well predicted by the ECMWF-SEAS5 prediction system during early winter. Furthermore, we noted the positive TWCIO heating anomalies tend to favor the positive North Atlantic Oscillation (NAO) condition in the North Atlantic region. This leads to the above normal Surface Air temperature (SAT) conditions, indicating to the mild early winter conditions over the European continent. The ECMWF-SEAS5 system shows a significant prediction skill of the SAT anomalies over the NAE region.</p>