Enhanced Climate Change Response of Wintertime North Atlantic Circulation, Cyclonic Activity, and Precipitation in a 25-km-Resolution Global Atmospheric Model

• DOI: 10.1175/jcli-d-19-0054.1
• Publication Date: 2019-09-03T18:05:19Z
• Authors: Alexander J. Baker; Reinhard Schiemann; Kevin I. Hodges; Marie-Estelle Demory; Matthew S. Miziel...; Malcolm J. Roberts; Len C. Shaffrey; Jane Strachan; Pier Luigi Vidale
• Keywords: Extratropical cyclone; Storm track; Atmospheric Circulation; Middle latitudes

Abstract Wintertime midlatitude cyclone activity and precipitation are projected to increase across northern Europe decrease over southern Europe, particularly the western Mediterranean. Greater confidence in these regional projections may be established by their replication state-of-the-art, high-resolution global climate models that resolve synoptic-scale dynamics. We evaluated representation of wintertime eddy-driven subtropical jet streams, extratropical activity, North Atlantic under historical (1985–2011) RCP8.5 sea surface temperature forcing an ensemble atmosphere-only HadGEM3-GA3.0 simulations, where horizontal atmospheric resolution is increased from 135 25 km. Under RCP8.5, (decreased) frequency (southern) occurrences a basinwide poleward shift upper-level westerly flow simulated. Increasing significantly enhances change responses. At 25-km resolution, enhanced changes large-scale circulation amplify increases (decreases) track density mean intensity Euro-Atlantic region RCP8.5. These synoptic with impact overall response heavy winter precipitation: wetter (drier) conditions also amplified at resolution. For example, reduction simulated Iberian Peninsula ~15% km but ~30% Conversely, more frequent high (ETC)-associated rates Scandinavia which This study provides evidence crucial consideration European projections.