Atmospheric (C-14)O - A tracer of OH concentration and mixing rates

• Published in: Journal of Geophysical Research 2000-06, Vol.105 (D12), p.15
• Main Authors: Quay, Paul, King, Stagg, White, David, Brockington, Melinda, Plotkin, Beth, Gammon, Richard, Gerst, Steven, Stutsman, John
• Format: Article
• Language: English
• ISSN: 0148-0227

Time series (C-14)O data sets were analyzed using a 2D atmospheric circulation and chemistry model in order to determine the tropospheric OH concentration that could explain the temporal and spatial trends in (C-14)O. Additionally, the interannual trend in tropospheric methyl chloroform concentration and the stratospheric time history of bomb (C-14)O2 were simulated by the model. The results of this analysis indicate that an average tropospheric OH concentration of about 10 exp 6 radicals/cu cm explains both the (C-14)O and methyl chloroform trends. The model-predicted (C-14)O concentrations, however, are sensitive to the rate of stratosphere-troposphere exchange and horizontal mixing in the troposphere. Model predictions of tropospheric (C-14)O at high latitudes improved when the stratosphere-troposphere exchange rate was slowed, based on the results of the stratospheric bomb (C-14)O2 model simulation. Substantial improvement in the model (C-14)O simulations occurred with increased horizontal diffusion rates in the troposphere and lower cosmogenic (C-14)O production rates. Significantly lower (C-14)O concentrations are observed in the Southern versus Northern Hemisphere. Model simulations indicate that either higher tropospheric horizontal mixing or higher OH concentrations in the Southern Hemisphere can explain the hemispheric asymmetry in (C-14)O. (Author)