Sensitivity Analysis of the MaTChM Atmospheric Chemistry Model
Area: Atmospheric Chemistry
Photochemical indicators for determination of O_3-NO_x-ROG sensitivity and their sensitivity to model parameters are studied for a variety of polluted conditions using a comprehensive mixed-phase chemistry box model and the novel automatic differentiation ADIFOR tool. The main chemical reaction pathways in all phases, interfacial mass transfer processes, and ambient physical parameters that affect the indicators are identified and analyzed. Condensed mixed-phase chemical mechanisms are derived from the sensitivity analysis. Our results show that cloud chemistry has a significant impact on the indicators and their sensitivities, particularly on those involving H_2O_2, HNO_3, HCHO, and NO_z. Caution should be taken when applying the established threshold values of indicators in regions with large cloud coverage. Among the commonly used indicators, NO_y and O_3/NO_y are relatively insensitive to most model parameters, whereas indicators involving H_2O_2, HNO_3, HCHO, and NO_z are highly sensitive to changes in initial species concentrations, reaction rate constants, equilibrium constants, temperature, relative humidity, cloud droplet size, and cloud water content.