EMS Annual Meeting Abstracts
Vol. 18, EMS2021-321, 2021, updated on 21 Mar 2023
https://doi.org/10.5194/ems2021-321
EMS Annual Meeting 2021
© Author(s) 2023. This work is distributed under
the Creative Commons Attribution 4.0 License.

Atmospheric response to Gulf Stream front shifting:impact of horizontal resolution in an ensemble of global climate models

Luca Famooss Paolini1,2, Alessio Bellucci3, Paolo Ruggieri1,4, Panos Athanasiadis1, and Silvio Gualdi1,5
Luca Famooss Paolini et al.
  • 1Euro-Mediterranean Center on Climate Change, Bologna, Italy (luca.famooss@cmcc.it)
  • 2Ca'Foscari University, Venezia, Italy
  • 3Institute of Atmospheric Sciences and Climate - National Research Council, Bologna, Italy
  • 4University of Bologna, Department of Physics and Astronomy, Bologna, Italy
  • 5Instituto Nazionale di Geofisica e Vulcanologia, Italy

Western boundary currents transport a large amount of heat from the Tropics toward higher latitudes; furthermore they are characterized by a strong sea surface temperature (SST) gradient. For such reasons they have been shown to be fundamental in influencing the climate of the Northern Hemisphere and its variability, and a  potentially relevant source of atmospheric predictability. General circulation models show deficiencies in simulating the observed atmospheric response to SST front variability. The atmospheric horizontal resolution has been recently proposed as a key element in understanding such differences. However, a multi-model analysis to systematically investigate differences between low-resolution and high-resolution atmospheric response to oceanic forcing is still lacking. The present work has the objective to fill this gap, analysing the atmospheric response to Gulf Stream SST front (GSF) shifting using data from recent High Resolution Model Intercomparison Project (HighResMIP). Ensembles of historical simulations performed with three atmospheric general circulation models (AGCMs) have been analysed, each conducted with a low-resolution (LR, about 1°) and a high-resolution (HR, about 0.25°) configuration. AGCMs have been forced with observed SSTs (HadISST2 dataset), available at daily frequency on a 0.25° grid, during 1950–2014. Results show atmospheric responses to the SST-induced diabatic heating anomalies that are strongly resolution dependent. In LR simulations a low-pressure anomaly is present downstream of the SST anomaly, while the diabatic heating anomaly is mainly balanced by meridional advection of air coming from higher latitudes, as expected for an extra-tropical shallow heat source. In contrast, HR simulations generate a high-pressure anomaly downstream of the SST anomaly, thus driving positive temperature advection from lower latitudes (not balancing diabatic heating). Along the vertical direction, both in LR and HR simulation, the diabatic heating in the interior of the atmosphere is balanced by upward motion south of GS SST front and downward motion north and further south of the Gulf Stream. Finally, LR simulations show a reduction in storm-track activity over the North Atlantic, whereas HR simulations show a meridional displacement of the storm-track considerably larger (yet in the same direction) than that of the SST front. HR simulations reproduce the atmospheric response obtained from observations, albeit weaker. This is a hint for the existence of a positive feedback between ocean and atmosphere, as proposed in previous studies. These findings are qualitatively consistent with previous results in literature and, leveraging on recent coordinated modelling efforts, shed light on the effective role of atmospheric horizontal resolution in modelling the atmospheric response to extra-tropical oceanic forcing.

How to cite: Famooss Paolini, L., Bellucci, A., Ruggieri, P., Athanasiadis, P., and Gualdi, S.: Atmospheric response to Gulf Stream front shifting:impact of horizontal resolution in an ensemble of global climate models, EMS Annual Meeting 2021, online, 6–10 Sep 2021, EMS2021-321, https://doi.org/10.5194/ems2021-321, 2021.

Displays

Display file

Supporters & sponsors