Large-scale chemical evolution of the Arctic vortex during the 1999/ 2000...

Pierce, B., J. Al-Saadi, T. D. Fairlie, M. Natarajan, V. L. Harvey, W. L. Grose, J. M. Russell, R. Bevilacqua, S. Eckermann, D. Fahey, P. Popp, E. Richard, R. Stimpfle, G. Toon, C. R. Webster, and J. W. Elkins (2003), Large-scale chemical evolution of the Arctic vortex during the 1999/ 2000 winter: HALOE/POAM III Lagrangian photochemical modeling for the SAGE III—Ozone Loss and Validation Experiment (SOLVE) campaign, J. Geophys. Res., 108, 8317, doi:10.1029/2001JD001063.

The LaRC Lagrangian Chemical Transport Model (LaRC LCTM) is used to simulate the kinematic and chemical evolution of an ensemble of trajectories initialized from Halogen Occultation Experiment (HALOE) and Polar Ozone and Aerosol Measurement (POAM) III atmospheric soundings over the SAGE III—Ozone Loss and Validation Experiment (SOLVE) campaign period. Initial mixing ratios of species which are not measured by HALOE or POAM III are specified using sunrise and sunset constituent CH4 and constituent PV regressions obtained from the LaRC IMPACT model, a global three dimensional general circulation and photochemical model. Ensemble averaging of the trajectory chemical characteristics provides a vortex-average perspective of the photochemical state of the Arctic vortex. The vortex-averaged evolution of ozone, chlorine, nitrogen species, and ozone photochemical loss rates is presented. Enhanced chlorine catalyzed ozone loss begins in mid-January above 500 K, and the altitude of the peak loss gradually descends during the rest of the simulation. Peak vortex averaged loss rates of over 60 ppbv/day occur in early March at 450 K. Vortex averaged loss rates decline after midMarch. The accumulated photochemical ozone loss during the period from 1 December 1999 to 30 March 2000 peaks at 450 K with net losses of near 2.2 ppmv. The predicted distributions of CH4, O3, denitrification, and chlorine activation are compared to the distributions obtained from in situ measurements to evaluate the accuracy of the simulations. The comparisons show best agreement when diffusive tendencies are included in the model calculations, highlighting the importance of this process in the Arctic vortex. Sensitivity tests examining the large-scale influence of orographically generated gravitywave temperature anomalies are also presented. Results from this sensitivity study show that mountain-wave temperature perturbations contribute an additional 2–8% O3 loss during the 1999/2000 winter.

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Atmospheric Composition Modeling and Analysis Program (ACMAP)