EGU24-3633, updated on 08 Mar 2024
https://doi.org/10.5194/egusphere-egu24-3633
EGU General Assembly 2024
© Author(s) 2024. This work is distributed under
the Creative Commons Attribution 4.0 License.

The Impact of Gulf Stream Moisture Flux Suppression on Atmospheric Blocks

Jamie Mathews1, Arnaud Czaja1, Frederic Vitart2, and Christopher Roberts2
Jamie Mathews et al.
  • 1Imperial College London, London, United Kingdom
  • 2European Centre for Medium-Range Weather Forecasts, Reading, United Kingdom

In this study, we explore the impact of oceanic moisture fluxes on atmospheric blocks using the ECMWF Integrated Forecast System (IFS). Artificially suppressing surface latent heat flux over the Gulf Stream region leads to a significant reduction (up to 30%) in atmospheric blocking frequency across the northern hemisphere. Affected blocks show a shorter lifespan (-6%), smaller spatial extent (-10%), and reduced intensity (-0.4%), with an increased detection rate (+14%). These findings are robust across various blocking detection thresholds. Analysis indicates a resolution-dependent response, with resolutions lower than Tco639 (∼18km) showing no significant change in blocking characteristics. Exploring the broader Rossby wave pattern, we observe that diminished moisture flux favors eastward propagation and higher zonal wavenumbers, while oceanic influence promotes stationary and westward-propagating waves with zonal wavenumber 3. This study underscores the critical role of western boundary current’s moisture fluxes in modulating atmospheric blocking and associated Rossby wave dynamics.

How to cite: Mathews, J., Czaja, A., Vitart, F., and Roberts, C.: The Impact of Gulf Stream Moisture Flux Suppression on Atmospheric Blocks, EGU General Assembly 2024, Vienna, Austria, 14–19 Apr 2024, EGU24-3633, https://doi.org/10.5194/egusphere-egu24-3633, 2024.

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supplementary materials version 1 – uploaded on 17 Apr 2024
  • CC1: Comment on EGU24-3633, Panos J. Athanasiadis, 17 Apr 2024

    Hi Jamie,

    I look forward to your presentation. To anticipate a question I would probably ask: how does the circulation response (e.g. Z500 and U850) look like in these experiments in respect to the control simulations? If the surface heating reduction is applied at the GSE area, is the response in the HR simulations consistent with Famoos Paolini et al. (2022, https://journals.ametsoc.org/view/journals/clim/35/18/JCLI-D-21-0530.1.xml) and Wills et al. (2024, https://iacweb.ethz.ch/staff/rjnglin/papers/2023_Wills_etal_NATLx8_large_scale.pdf)?

  • CC2: Comment on EGU24-3633, Panos J. Athanasiadis, 17 Apr 2024

    It would be interesting, I think, to proportionally suppress the sensible heat flux (in a separate experiment, or in combination with the moisture flux) and also do so for other areas (e.g. the beginning of the NAC, see discussion section in https://journals.ametsoc.org/view/journals/clim/35/21/JCLI-D-21-0515.1.xml and references thereof, including https://doi.org/10.5194/wcd-2-819-2021.).