Tailored reduced kinetic mechanisms for atmospheric chemistry modeling

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Reduced chemical kinetic mechanisms are essential for atmospheric chemistry modeling where the use of explicit kinetic schemes is too computationally demanding. By tailoring mechanisms to specific cases, the size of the mechanism can be kept small, without significant loss of accuracy in predictions of selected species’ concentrations. In the present work, we present small kinetic mechanisms tailored to specific cases, using a novel method. The reduced mechanisms are generated by applying the method to several cases previously described in the literature and their performance in box model simulations are evaluated. The characteristics of the reduced mechanisms are examined. In addition, the method's sensitivity towards time scales, choice of trace gas species of interest, and NOx regime are investigated. The reduced mechanisms include 10%–30% of all the reactions in the relevant subset of the detailed chemical mechanism. Simulations with the reduced mechanisms typically yield no loss in accuracy of ozone concentration predictions and less than a 10% accuracy loss for the concentration predictions of nitrogen oxides for the cases over as long as five simulated days. Mechanisms generated to predict the concentrations of few species, over short time scales, in high NOx conditions, and with no isoprene, generally include fewer reactions than mechanisms generated to predict the concentrations of several species, over long time scales, in lowNOx, isoprene rich conditions.