Teleconnection of the winter Atlantic Niño to the North Atlantic-European atmospheric circulation

Tropical Atlantic Variability (TAV) exerts a significant influence on the climate of different regions. Understanding these teleconnections and their impacts can improve predictability, particularly in the North Atlantic-European (NAE) region. The Atlantic Niño (ATLN) or Equatorial Mode is known for being the dominant pattern of TAV. This study aims at exploring the atmospheric response to winter ATLN, as it has been much less documented than the summer ATLN. Coupled simulations and atmosphere-only experiments with the CMIP6 version of the climate model EC-EARTH (T255L91) have been performed and analysed to revisit the ATLN-NAE teleconnection and further improve process understanding. The coupled simulation consists in a 250-year long integration, after spin-up, with fixed radiative forcing at present conditions; the atmospheric response is estimated by linear regression onto the winter ATLN index defined by Okumura&Xie. The atmosphere-only experiments comprise two 150-year long integrations keeping again the radiative forcing fixed, a control run with climatological SSTs and a sensitivity run prescribing the observed ATLN with climatology elsewhere; the atmospheric response is evaluated by comparing both experiments. Results show a local Gill-type structure, symmetrically straddling the equator, whose amplitude increases from November-December to January-February. In the extratropics, the upper-tropospheric circulation displays a dipolar structure with cyclonic anomalies at mid-latitudes and anticyclonic anomalies at subpolar latitudes, which is different from the North Atlantic Oscillation (NAO). The associated precipitation anomalies show a robust and approximately-linear signal on the European continent.