HR: 1340h
AN: SA23A-1130    [Abstracts]
TI: Simulations of Medium Energy Electron Precipitation in WACCM
AU: * Fang, X
EM: xiaohua.fang@lasp.colorado.edu
AF: University of Colorado, LASP, 392 UCB, Boulder, CO 80309, United States
AU: Randall, C E
EM: cora.randall@lasp.colorado.edu
AF: University of Colorado, LASP, 392 UCB, Boulder, CO 80309, United States
AU: Mills, M J
EM: michael.mills@lasp.colorado.edu
AF: University of Colorado, LASP, 392 UCB, Boulder, CO 80309, United States
AU: Marsh, D R
EM: marsh@ucar.edu
AF: National Center for Atmospheric Research, P.O.Box 3000, Boulder, CO 80307, United States
AU: Bardeen, C G
EM: bardeenc@colorado.edu
AF: University of Colorado, LASP, 392 UCB, Boulder, CO 80309, United States
AU: Jackman, C H
EM: charles.h.jackman@nasa.gov
AF: NASA Goddard Space Flight Center, Code 916, Greenbelt, MD 20771, United States
AB: The NOx catalytic cycle is the primary O3 destruction mechanism throughout most of the stratosphere. Oxidation of nitrous oxide (N2O), emitted at the ground and transported to the stratosphere, is thought to be the largest source of stratospheric NOx. However, observations during the last two decades have shown that NOx produced by energetic particle precipitation (EPP-NOx) in the mesosphere and lower thermosphere (MLT) can descend to the stratosphere during the polar night. Estimates based on satellite measurements of NOx suggest that up to 40% of the NOx in the stratospheric polar region might be derived from EPP on an annual basis. Understanding stratospheric O3 distributions thus requires quantification of the contribution of EPP-NOx to the stratosphere. This presentation describes recent work to investigate the descent of EPP-NOx to the stratosphere using the Whole Atmosphere Community Climate Model (WACCM) from the National Center for Atmospheric Research (NCAR). WACCM is a coupled chemistry climate model extending in altitude from the Earth's surface up to 140 km. It includes comprehensive, interactive chemistry of the middle atmosphere, and is thus well-suited for these studies. In this presentation, we describe a new parameterization of medium energy (~30-300 keV) electron precipitation in WACCM, which produces EPP-NOx in the mesosphere. We will describe the calculation of ionization rates, including spatial distributions, and subsequent production of NOx. The importance of medium energy electron precipitation in producing NOx and modifying stratospheric ozone and temperature will be assessed, and compared to the effects of EPP-NOx produced by auroral electrons.
DE: 0340 Middle atmosphere: composition and chemistry
DE: 0341 Middle atmosphere: constituent transport and chemistry (3334)
DE: 2716 Energetic particles: precipitating
DE: 3334 Middle atmosphere dynamics (0341, 0342)
SC: SPA-Aeronomy [SA]
MN: 2007 Fall Meeting