4-9 September 2022, Bonn, Germany
EMS Annual Meeting Abstracts
Vol. 19, EMS2022-19, 2022, updated on 13 Apr 2023
EMS Annual Meeting 2022
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

How is the extratropical circulation affected by reduced Atlantic and Pacific land-sea thermal contrast?

Alice Portal1,2, Claudia Pasquero1,3, Fabio D'Andrea2, Paolo Davini3, Mostafa Hamouda4,5, and Gwendal Rivière2
Alice Portal et al.
  • 1University of Milano-Bicocca, Department of Earth and Environmental Sciences, Milan, Italy
  • 2Laboratoire de Météorologie Dynamique/IPSL, École Normale Supérieure, PSL Research University, Sorbonne Université, École Polytechnique, IP Paris, CNRS, Paris, France
  • 3Consiglio Nazionale delle Ricerche, Istituto di Scienze dell’Atmosfera e del Clima (CNR-ISAC), Torino, Italy
  • 4Institute for Atmospheric and Environmental Sciences, Goethe University Frankfurt, Frankfurt am Main, Germany
  • 5Astronomy and Meteorology Department, Faculty of Science, Cairo University, Cairo, Egypt

Long-term projections of the future climate display a robust reduction of winter land-sea thermal contrast in the Northern Hemisphere (NH), caused by a faster warming of the cold continents compared to the warm oceans. The reduction is expected to be strong in the extratropics, a region where the thermal contrast is relevant for maintaining the strong baroclinicity near the western coasts of the continents and for shaping the NH jets and large-scale stationary waves.

In this work idealised perpetual-winter experiments characterised by a reduced land-sea thermal contrast are compared to control simulations featuring a thermal contrast similar to that observed in present-day climate. We use an intermediate-complexity AGCM with prescribed sea-surface and land temperatures. Warm temperature anomalies in East Asia and/or North America set a reduced thermal contrast in the whole NH or in individual NH sectors. We find that the Pacific-sector land-sea thermal contrast is by far more important than the Atlantic one for the large-scale mid-latitude circulation, as it impacts strongly the jet streams and the stationary planetary waves. While the local effects are coherent with the changes in baroclinicity brought by the surface forcing, the remote effects seem to be mediated by the response of the thermal and orographic components of the stationary waves. Based on the idealised-modelling results it is possible to hypothesise how the projected change in winter land-sea thermal contrast influences climate scenarios for the end of the XXI century. This factor has been rarely considered as a possible source of dynamical changes for the mid-latitude winter season.

How to cite: Portal, A., Pasquero, C., D'Andrea, F., Davini, P., Hamouda, M., and Rivière, G.: How is the extratropical circulation affected by reduced Atlantic and Pacific land-sea thermal contrast?, EMS Annual Meeting 2022, Bonn, Germany, 5–9 Sep 2022, EMS2022-19, https://doi.org/10.5194/ems2022-19, 2022.

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