On the linkages between the tropospheric isentropic slope and eddy fluxes of heat during Northern Hemisphere winter

Thompson, David W. J. and Birner, Thomas (2012) On the linkages between the tropospheric isentropic slope and eddy fluxes of heat during Northern Hemisphere winter. Journal of the Atmospheric Sciences, 69 (6). 1811–1823. ISSN 0022-4928

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Abstract

Previous studies have demonstrated the key role of baroclinicity and thus the isentropic slope in determining the climatological-mean distribution of the tropospheric eddy fluxes of heat. Here the authors examine the role of variability in the isentropic slope in driving variations in the tropospheric eddy fluxes of heat about their long-term mean during Northern Hemisphere winter. On month-to-month time scales, the lower-tropospheric isentropic slope and eddy fluxes of heat are not significantly correlated when all eddies are included in the analysis. But the isentropic slope and heat fluxes are closely linked when the data are filtered to isolate the fluxes due to synoptic (<10 days) and low-frequency (>10 days) time scale waves. Anomalously steep isentropic slopes are characterized by anomalously poleward heat fluxes by synoptic eddies but anomalously equatorward heat fluxes by low-frequency eddies. Lag regressions based on daily data reveal that 1) variations in the isentropic slope precede by several days variations in the heat fluxes by synoptic eddies and 2) variations in the heat fluxes due to both synoptic and low-frequency eddies precede by several days similarly signed variations in the momentum flux at the tropopause level. The results suggest that seemingly modest changes in the tropospheric isentropic slope drive significant changes in the synoptic eddy heat fluxes and thus in the generation of baroclinic wave activity in the lower troposphere. The linkages have implications for understanding the extratropical tropospheric eddy response to a range of processes, including anthropogenic climate change, stratospheric variability, and extratropical sea surface temperature anomalies.

Item Type: Article
Uncontrolled Keywords: annular mode,atmospheric circulation,large-scale motions,atmospheric waves,stratophere-troposphere coupling,climate variability,sdg 13 - climate action ,/dk/atira/pure/sustainabledevelopmentgoals/climate_action
Faculty \ School: Faculty of Science > School of Environmental Sciences
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Depositing User: LivePure Connector
Date Deposited: 07 Jun 2022 14:30
Last Modified: 13 Jun 2022 00:26
URI: https://ueaeprints.uea.ac.uk/id/eprint/85417
DOI: 10.1175/JAS-D-11-0187.1

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