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Dynamically forced increase of tropical upwelling in the lower stratosphere

Garny, Hella and Dameris, Martin and Randel, William and Bodeker, Greg and Deckert, Rudolf (2011) Dynamically forced increase of tropical upwelling in the lower stratosphere. Journal of the Atmospheric Sciences, 68, pp. 1214-1233. DOI: 10.1175/2011JAS3701.1.

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Official URL: http://journals.ametsoc.org/doi/abs/10.1175/2011JAS3701.1

Abstract

Drivers of upwelling in the tropical lower stratosphere are investigated using the E39C-A chemistry– climate model. The climatological annual cycle in upwelling and its wave forcing are compared to the interim ECMWF Re-Analysis (ERA-Interim). The strength in tropical upwelling and its annual cycle can be largely explained by local resolved wave forcing. The climatological mean forcing is due to both stationary planetaryscale waves that originate in the tropics and extratropical transient synoptic-scale waves that are refracted equatorward. Increases in atmospheric greenhouse gas (GHG) concentrations to 2050 force a year-round positive trend in tropical upwelling, which maximizes in the lowermost stratosphere. Tropical ascent is balanced by downwelling between 208 and 408. Strengthening of tropical upwelling can be explained by stronger local forcing by resolved wave flux convergence, which is driven in turn by processes initiated by increases in tropical sea surface temperatures (SSTs). Higher tropical SSTs cause a strengthening of the subtropical jets and modification of deep convection affecting latent heat release. While the former can modify wave propagation and dissipation, the latter affects tropical wave generation. The dominant mechanism leading to enhanced vertical wave propagation into the lower stratosphere is an upward shift of the easterly shear zone due to the strengthening and upward shift of the subtropical jets.

Document Type:Article
Title:Dynamically forced increase of tropical upwelling in the lower stratosphere
Authors:
AuthorsInstitution or Email of Authors
Garny, HellaDLR-IPA
Dameris, MartinDLR-IPA
Randel, WilliamNCAR Boulder, CO, USA
Bodeker, GregBodeker Scientific, Alexandra, NZ
Deckert, RudolfDLR-IPA
Date:2011
Journal or Publication Title:Journal of the Atmospheric Sciences
Volume:68
DOI:10.1175/2011JAS3701.1
Page Range:pp. 1214-1233
Status:Published
Keywords:Brewer-Dobson circulation, numerical modelling, chemistry-climate model
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Earth Observation
DLR - Research area:Raumfahrt
DLR - Program:R EO - Erdbeobachtung
DLR - Research theme (Project):R - Vorhaben Atmosphären- und Klimaforschung
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Atmospheric Dynamics
Deposited By: Prof. Dr. rer. nat. Martin Dameris
Deposited On:18 Nov 2011 15:38
Last Modified:12 Dec 2013 21:24

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