SENSITIVITY ANALYSIS OF A MIXED-PHASE CHEMICAL MECHANISM USING AUTOMATIC DIFFERENTIATION

A sensitivity analysis of a comprehensive mixed-phase chemical mechani sm is conducted under a variety of atmospheric conditions. The local s ensitivities of gas and aqueous phase species concentrations with resp ect to a variety of model parameters are calculated using the novel au tomatic differentiation ADIFOR tool. The main chemical reaction pathwa ys in all phases, interfacial mass transfer processes, and ambient phy sical parameters that affect tropospheric O-3 formation and O-3-precur sor relations under all modeled conditions are identified and analyzed . The results show that the presence of clouds not only reduces many g as phase species concentrations and the total oxidizing capacity but a lters O-3-precursor relations. Decreases in gas phase concentrations a nd photochemical formation rates of O-3 can be up to 9% and 100%, resp ectively, depending on the preexisting atmospheric conditions. The dec rease in O-3 formation is primarily caused by the aqueous phase reacti ons of O-2(-) with dissolved HO2 and O-3 under most cloudy conditions.