Evaluation of Whole Atmosphere Community Climate Model simulations of ozone during Arctic winter 2004–2005

We suggest that the model under-predicts ClONO2 early in the winter, which leads to less heterogeneous processing and too little activated chlorine. Model HCl could also be overestimated due to an underestimation of HCl uptake into supercooled ternary solution (STS) particles. In late winter, the model overestimates gas-phase HNO3, and thus NOy, which leads to an over-prediction of ClONO2 (under-prediction of activated chlorine).

A sensitivity study, in which temperatures for heterogeneous chemistry reactions were reduced by 1.5 K, shows significant improvement of modeled ozone. Chemical ozone loss is inferred from the MLS observations using the pseudo-passive subtraction approach. The inferred ozone loss using this method is in agreement with or less than previous independent results for the Arctic winter of 2004–2005, reaching 1.0 ppmv on average and up to 1.6 ppmv locally in the polar vortex.