HR: 0800h
AN: A31A-0039    [Abstracts]
TI: ATMOSPHERIC CHEMISTRY AND CLIMATE RESPONSE TO NOy SOURCE DUE TO ENEGETIC ELECTRON PRECIPITATION
AU: Rozanov, E V
EM: e.rozanov@pmodwrc.ch
AF: PMOD/WRC, Dorfstrasse 33, Davos Dorf, CH-7260 Switzerland
AU: Callis, L B
EM: LBOS2@aol.com
AF: Consultant, 613 W. Riverview Dr., Suffolk, VA 23434 United States
AU: Yang, F
EM: fanglin.yang@noaa.gov
AF: Environmental Modeling Center NCEP, 5200 Auth Road, Camp Springs, MD 20746 United States
AU: * Schlesinger, M E
EM: schlesin@atmos.uiuc.edu
AF: UIUC, 105 S. Gregory Str, Urbana, IL 61801 United States
AU: Andronova, N G
EM: natasha@atmos.uiuc.edu
AF: UIUC, 105 S. Gregory Str, Urbana, IL 61801 United States
AU: Zubov, V A
EM: zubov@main.mgo.rssi.ru
AF: Main Geophysical Observatory, 7 Karbyshev Str., St. Petersburg, 194018 Russian Federation
AB: The simulated response of the stratospheric ozone and temperature to the decadal scale solar UV variability is underestimated by virtually all models in comparison with observational data, suggesting that one or more important physical mechanisms are missing. We have introduced an additional NOy source caused by energetic electron precipitation events (EEP) into the fully-coupled UIUC Chemistry-Climate model, extending up into the lower thermosphere, to estimate the potential significance of this process for the chemical composition, temperature and dynamics of the atmosphere. The intensity of the additional NOy source is derived from the satellite measurements of energetic electron precipitation in 1987, a year with relatively low fluxes. Comparison of the 10-year long annually repeating run with EEP switched on against a similar control run without the additional source of NOy reveals statistically significant changes of the atmospheric state. In particular, the annual mean NOy mixing ratio increases by about 3 ppbv in the middle stratosphere and mesosphere over the tropical and middle latitudes. In the upper stratosphere over the polar regions, where the downward transport is generally more intense, the simulated NOy enhancement reaches 10 ppbv. The increase of NOy results in an intensification of the ozone destruction and decrease of the ozone mixing ratio mostly in the middle and lower stratosphere by up to 5% over midlatitudes and up to 20% over southern high-latitudes. Accordingly, the total ozone decrease is the most pronounced over southern high-latitudes (~20%) and northern mid-latitudes (~8%), while in the tropical area the total ozone depletion is about 5% and only marginally statistically significant. The pattern of the temperature response consists of a ~0.5 K cooling in the middle stratosphere over the tropics and up to 2 K over high-latitudes. Some changes in the tropospheric circulations and surface air temperature are also detectable. These results suggest that the magnitude of the ozone and temperature changes due to EEP events can exceed the effects from solar UV fluxes within the present model. They also suggest that the combined effect of the EEP and UV perturbations can be close to the atmospheric response obtained from the observations.
DE: 2455 Particle precipitation
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