Dynamics of Anomalous Stratospheric Eddy Heat Flux Events in an Idealized Model

Extreme stratospheric eddy and sudden stratospheric warming (SSW) events both involve anomalous stratospheric eddy heat flux. The cause of the anomaly has been hypothesized to be due to tropospheric or stratospheric dynamics. Here, ensemble spectral nudging experiments in a dry dynamical-core model...

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Bibliographic Details
Published in:Journal of the atmospheric sciences 2020-06, Vol.77 (6), p.2187-2202
Main Authors: Dunn-Sigouin, Etienne, Shaw, Tiffany
Format: Article
Language:English
Subjects:
Climatology
Dynamics
Eddies
Eddy heat flux
Experiments
Fluctuations
Heat
Heat flux
Heat transfer
Induction heating
Ozone
Stratosphere
Stratospheric dynamics
Stratospheric warming
Temperature
Troposphere
Tropospheric waves
Wave interaction
Wavelengths
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Summary:Extreme stratospheric eddy and sudden stratospheric warming (SSW) events both involve anomalous stratospheric eddy heat flux. The cause of the anomaly has been hypothesized to be due to tropospheric or stratospheric dynamics. Here, ensemble spectral nudging experiments in a dry dynamical-core model are used to quantify the role of the troposphere versus the stratosphere. The experiments focus on the wavenumber-1 heat flux since it dominates the anomalous stratospheric eddy heat flux during both events. Nudging the stratospheric zonal-mean flow does not account for the anomalous stratospheric wave-1 heat flux. Nudging either tropospheric wave-1 or higher-order wavenumbers ( k ≥ 2) accounts for a large fraction of the anomalous stratospheric wave-1 heat flux. Mechanism denial experiments, whereby tropospheric eddies (wave 1 or k ≥ 2) are nudged and the zonal-mean flow is fixed to climatology, suggest the climatological stratospheric zonal-mean flow is sufficient to account for the anomalous stratospheric wave-1 heat flux and wave–wave interaction plays a role in generating the anomalous tropospheric wave-1 source. Taken together, the experiments suggest the troposphere dominates the anomalous stratospheric eddy heat flux during extreme stratospheric eddy and SSW events while the stratospheric zonal-mean flow plays secondary role.
ISSN:0022-4928
1520-0469
DOI:10.1175/JAS-D-19-0231.1