HR: 0800h
AN: A31A-0042    [Abstracts]
TI: Chemical Effects in 11-Year Solar Cycle Simulations With the Freie Universit\"at Berlin Climate Middle Atmosphere Model With Interactive Chemistry (FUB-CMAM-CHEM)
AU: * Langematz, U
EM: langematz@strat01.met.fu-berlin.de
AF: Institut f\"ur Meteorologie Freie Universit\"at Berlin, Carl-Heinrich-Becker-Weg 6-10, Berlin, 12265 Germany
AU: Grenfell, J L
EM: grenfell@strat01.met.fu-berlin.de
AF: Institut f\"ur Meteorologie Freie Universit\"at Berlin, Carl-Heinrich-Becker-Weg 6-10, Berlin, 12265 Germany
AU: Matthes, K
EM: kmatthes@ucar.edu
AF: Institut f\"ur Meteorologie Freie Universit\"at Berlin, Carl-Heinrich-Becker-Weg 6-10, Berlin, 12265 Germany
AU: Matthes, K
EM: kmatthes@ucar.edu
AF: National Center for Atmospheric Research, 1850 Table Mesa Drive, Boulder, CO 80305 United States
AB: Parameterisation of NOx transport from the mesosphere to the stratosphere may be important when simulating the 11-year solar cycle influence upon stratospheric ozone in climate- chemistry models (CCMs). The downward NOx transport occurs primarily in the wintertime polar night jet (PNJ) hence may lead to a characteristic positive dipole ozone signal (higher ozone at solar maximum) in the annual mean. Such a dipole, peaking at 40-45 km near 60øN and 60øS, has been noted in some satellite observations. In this talk we present results of 11-year solar cycle simulations of the Freie Universit\"at Berlin Middle Atmosphere Model with interactive chemistry (FUB-CMAM-CHEM). Variations in NOx transport from the mesosphere were parameterised by including an idealised NOx source at high latitudes above 70 km. The NOx source represents the effect of high-energy electron precipitation associated with intense solar wind streams which lead to decreased NOx (hence increased ozone) near solar maximum. Other NOx sources, associated with low and medium energy electrons arising in the aurora tend to have the opposite effect (increased NOx at solar maximum) and are not included in this study . The model calculates the observed dipole ozone signal which is however stronger than that observed, probably due to the neglect of the compensating effects of low and medium energy electrons. The model further calculates a negative ozone signal in the lower stratosphere (~20 km) near the equator which is also suggested by some satellite observations but occurs a little higher up (25-30 km). Our results imply that the negative ozone signal in the model arises at least partly via a chemical effect in which ozone-destroying chemicals are released from their reservoirs via enhanced insolation at solar maximum. In the mesosphere a decrease in ozone is calculated at solar maximum associated with the classical HOx cycle enhanced via Lyman-alpha photolysis of water vapour.
DE: 3334 Middle atmosphere dynamics (0341, 0342)
DE: 1620 Climate dynamics (3309)
DE: 1650 Solar variability
DE: 0341 Middle atmosphere--constituent transport and chemistry (3334)
SC: Atmospheric Sciences [A]
MN: 2004 AGU Fall Meeting