Tropospheric pathways of the late-winter ENSO teleconnection to Europe

Abstract

The late-winter signal associated with the El Niño-Southern Oscillation (ENSO) over the European continent is unsettled. Two main anomalous patterns of sea-level pressure (SLP) can be identified: a “wave-like” pattern with two opposite-signed anomalies over Europe, and a pattern showing a single anomaly (“semi-isolated”). In this work, potential paths of the tropospheric ENSO teleconnection to Europe and their role in favoring a more wave-like or semi-isolated pattern are explored. Outputs from historical runs of two versions of the MPI-ESM coupled model, which simulate these two types of patterns, are examined. A novel ray-tracing approach that accounts for zonal asymmetries in the background flow is used to test potential propagation paths in these simulations and in observations; three source regions are considered: the tropical Pacific, the North America/North Atlantic, and the tropical Atlantic. The semi-isolated pattern is suggested to be related to the well-known Rossby wave train emanating from the tropical Pacific, either via a split over northern North America or via reflection due to inhomogeneities in the background flow. The wave-like pattern, in turn, appears to be related to a secondary wave train emerging from the tropical Atlantic. The competition between these two pathways contributes to determining the actual surface response.

Synergistic effect of boreal autumn SST over the tropical and South Pacific and winter NAO on winter precipitation in the southern Europe

“…Also, many studies have investigated the influence of Pacific Ocean on South Europe and Mediterranean region. ENSO is an important interannual climate variability influencing precipitation over Atlantic-Europe region [22][23][24] . Previous studies have found increased wintertime precipitation over Britain, France, and Germany during an El Niño, but decreased precipitation over Scandinavia 25 .…”