(53a) Identifying Reaction Regimes in Atmospheric Chemical Transport Models for Mechanism Reduction

As atmospheric chemists continue to better understand the details of the reactions associated with organic gaseous and aerosol components, we must continue to develop novel approaches to allow adequate representations of this increasingly complex chemistry in computational models.   This work presents the first steps towards the development a new approach using defined chemical regimes in a three-dimensional chemical transport model to provide a balance of computational efficiency and mechanism detail.  This work identifies specific chemical regimes based on a variety of characteristics including, but not limited to, season, temperature, relative ambient concentrations, land-cover, and region.  These chemical reaction regimes are defined or identified based on a determination of the relative dominance of different classes of reactions.  This allows identification of both the most and least dominant reactions within the regimes. 

This work includes an initial application of this method of regime identification using a regional chemical transport model, CAMx, over the continental United States, including both diurnal and seasonal temporal impacts on regime identification and classification.  Spatial we include impacts of a variety of spatial factors from land-use (for instance, urban vs. rural) to regional specifications (for instance, Northeastern vs. Southwestern United States).  Several  This work investigates the relationships between the instantaneous chemical reaction rates and contributions. Future work will account for the longer-term impacts of reactions in each regime to ensure that small instantaneous impacts with larger long-term impacts are not being neglected.

We have identified four groups of species whose reaction rates show the largest temporal and spatial variability: acetylperoxy radical, isoprene oxidation, glyoxal, and olefin reactions.