Sensitivity of the winter North Atlantic-European atmospheric circulation to Tropical North Atlantic SST anomalies

One of the leading modes of sea surface temperature (SST) variability in the Tropical Atlantic consists of a meridional pattern dominated by anomalies in the Tropical North Atlantic (TNA). It is strongly coupled with the North Atlantic Oscillation (NAO); in addition to be one of the lobes of the NAO-induced SST tripole, it is thought to be an integral part of the positive ocean feedback onto the atmosphere (i.e. NAO-like response). This study aims at exploring the contribution of two SST areas on the atmospheric response to TNA: the Subtropical North Atlantic (SNA) in the eastern basin, and the Caribbean region (CBBN) in the western basin. A set of sensitivity experiments has been performed with the intermediate-complexity atmosphere model SPEEDY (T30L8), keeping fixed the radiative forcing at present-day climate conditions. Atmosphere-only simulations comprise a control run with observed climatological SSTs over 1980-2010 (CTRL), a first sensitivity run prescribing the whole observed TNA pattern with climatology elsewhere (FULL), and two additional sensitivity runs similar to FULL but splitting the observed TNA pattern into its eastern (SNA) and western (CBBN) components, namely east and west of 60ºW. Two-hundred members have been completed for each simulation, covering the extended winter season from November to March. Further, a twin set of experiments has been performed coupling SPEEDY to a slab ocean model (SPEEDY-SOM) in order to assess the impact of extratropical air-sea interaction on the atmospheric response to TNA, SNA and CBBN. Preliminary results suggest that the Caribbean region plays an important role in the tropical-extratropical teleconnection.