HR: 14:25h
AN: SA33A-04 INVITED     [Abstracts]
TI: Mesospheric influence on stratospheric ozone: energetic particle precipitation
AU: * Randall, C E
EM: randall@lasp.colorado.edu
AF: University of Colorado, LASP, UCB 392, Boulder, CO 80309-0392 United States
AB: In the stratosphere between about 25 and 40 km, the NOx (NO + NO2) catalytic cycle is the main ozone loss mechanism. Crucial to our attribution and prediction of stratospheric ozone trends, therefore, is understanding stratospheric NOx variability. The mesosphere plays a critical, but still poorly quantified, role in controlling stratospheric NOx. The primary source of stratospheric NOx is oxidation of N2O. A second source is energetic particle production of NO. Highly energetic protons or electrons are required to produce NO directly in the stratosphere, and since these occur relatively rarely, they are unlikely to play a major role in determining ozone trends. Energetic particle production of NO in the mesosphere or thermosphere, however, is much more routine, and descent of the NO so produced can significantly perturb stratospheric ozone distributions. This presentation focuses on the role that NOx descent in the mesosphere plays in influencing stratospheric ozone variability. The long-term effect of energetic particles on stratospheric ozone depends on the energy (deposition altitude) and flux (NOx production) of energetic particles, the timing and location of the impacts (e.g., in sunlight or not), and on the efficiency with which the NOx is transported downward. Using satellite observations and modeling, all of these different criteria are investigated with a view toward understanding long-term effects of mesospheric processes on stratospheric ozone. Particular emphasis is placed on the contribution of medium energy electrons (30-300 keV), which deposit their energy in the mesosphere, to observed NOx variability.
DE: 0340 Middle atmosphere--composition and chemistry
DE: 0341 Middle atmosphere--constituent transport and chemistry (3334)
DE: 0342 Middle atmosphere--energy deposition
DE: 2716 Energetic particles, precipitating
DE: 3360 Remote sensing
SC: SPA-Aeronomy [SA]
MN: 2005 Joint Assembly