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Meridional-energy-transport extremes and the general circulation of Northern Hemisphere mid-latitudes: dominant weather regimes and preferred zonal wavenumbers

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posted on 2024-03-06, 14:29 authored by V Lembo, F Fabiano, VM Galfi, RG Graversen, V Lucarini, G Messori
The extratropical meridional energy transport in the atmosphere is fundamentally intermittent in nature, having extremes large enough to affect the net seasonal transport. Here, we investigate how these extreme transports are associated with the dynamics of the atmosphere at multiple spatial scales, from planetary to synoptic. We use the ERA5 reanalysis data to perform a wavenumber decomposition of meridional energy transport in the Northern Hemisphere mid-latitudes during winter and summer. We then relate extreme transport events to atmospheric circulation anomalies and dominant weather regimes, identified by clustering 500hPa geopotential height fields. In general, planetary-scale waves determine the strength and meridional position of the synoptic-scale baroclinic activity with their phase and amplitude, but important differences emerge between seasons. During winter, large wavenumbers (kCombining double low line2-3) are key drivers of the meridional-energy-transport extremes, and planetary- and synoptic-scale transport extremes virtually never co-occur. In summer, extremes are associated with higher wavenumbers (kCombining double low line4-6), identified as synoptic-scale motions. We link these waves and the transport extremes to recent results on exceptionally strong and persistent co-occurring summertime heat waves across the Northern Hemisphere mid-latitudes. We show that the weather regime structures associated with these heat wave events are typical for extremely large poleward-energy-transport events.

Funding

Tipping Points in the Earth System

European Commission

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compound Climate Extremes in North America and Europe: from dynamics to predictability

European Research Council

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The role of the atmospheric energy transport in recent Arctic climate change

The Research Council of Norway

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History

Citation

Weather Clim. Dynam., 3, 1037–1062, https://doi.org/10.5194/wcd-3-1037-2022, 2022.

Author affiliation

Comp' & Math' Sciences

Version

  • VoR (Version of Record)

Published in

Weather and Climate Dynamics

Volume

3

Pagination

1037 - 1062

Publisher

Copernicus GmbH

eissn

2698-4016

Acceptance date

2022-07-28

Copyright date

2022

Available date

2024-03-06

Language

en

Deposited by

Professor Valerio Lucarini

Deposit date

2024-02-26

Data Access Statement

ERA5 Reanalysis data are publicly accessible via Copernicus Data Storage (https://doi.org/10.24381/cds.adbb2d47, Hersbach et al., 2018). The computation of meridional energy transport and its wavenumber decomposition was performed at the ECMWF data server and stored at the NIRD storage facility provided by the Norwegian e-infrastructure for research and education UNINETT Sigma2 under the project NS9063K. This can be accessed upon request to Rune Grand Graversen.

Rights Retention Statement

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