HR: 08:20h
AN: A11E-02 INVITED     [Abstracts]
TI: The Transfer of the Solar Signal From the Stratosphere to the Troposphere: Northern Winter
AU: * Matthes, K
EM: kmatthes@ucar.edu
AF: Freie Universitaet Berlin, Institut fuer Meteorologie, Carl-Heinrich-Becker-Weg 6-10, Berlin, 12165 Germany
AU: * Matthes, K
EM: kmatthes@ucar.edu
AF: National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder, CO 80305 United States
AB: The atmospheric response to the solar cycle has been previously investigated with the Freie Universitaet Berlin Climate Middle Atmosphere Model (FUB-CMAM) using prescribed spectral solar UV and ozone changes as well as prescribed equatorial, QBO-like winds. The solar signal is transferred from the upper to the lower stratosphere through a modulation of the polar night jet and the Brewer-Dobson circulation. The interaction between QBO and solar signal are comparable to estimates from observations. These model experiments are further investigated here to show the transfer of the solar signal from the lower stratosphere to the troposphere and down to the surface during northern hemisphere winter. During October and November, the model response is concentrated in the stratosphere. However, during December and January there is a significant response in tropospheric circulation which decays in February. Analysis focuses on the transition from the early winter stratospheric-dominated signal to the mid-winter tropospheric-dominated signal. The results show that the stratosphere has an important effect on tropospheric changes through a stratospheric-tropospheric circulation regime that develops in December and January and disappears in February. The Brewer-Dobson circulation provides the link between low and high latitude changes as well as between upper and lower stratospheric changes. Dynamical heating in the tropical lower stratosphere induces circulation changes (changes in tropopause height, static stability, convection and precipitation) in the tropical troposphere and down to the surface. These effects are identified as indirect effects from the stratosphere mainly because the sea surface temperatures are identical in the solar maximum and minimum experiment. The tropospheric changes confirm results from other simplified model studies as well as results from observations.
DE: 3334 Middle atmosphere dynamics (0341, 0342)
DE: 3362 Stratosphere/troposphere interactions
DE: 1610 Atmosphere (0315, 0325)
DE: 1620 Climate dynamics (3309)
DE: 1650 Solar variability
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting