Potential significance of photoexcited NO^sub 2^ on global air quality with the NMMB/BSC chemical transport model

Atmospheric chemists have recently focused on the relevance of the NO*^sub 2^ + H2O [arrow right] OH + HONO reaction to local air quality. This chemistry has been considered not relevant for the troposphere from known reaction rates until nowadays. New experiments suggested a rate constant of 1.7 × 10-^sup 13^ cm^sup 3^ molecule^sup -1^ s^sup -1^, which is an order of magnitude faster than the previously estimated upper limit of 1.2 × 10^sup -14^ cm^sup 3^ molecule^sup -1^ s^sup -1^, determined by Crowley and Carl (1997). Using the new global model, NMMB/BSC Chemical Transport Model (NMMB/BSC-CTM), simulations are presented that assess the potential significance of this chemistry on global air quality. Results show that if the NO*^sub 2^ chemistry is considered following the upper limit kinetics recommended by Crowley and Carl (1997), it produces an enhancement of ozone surface concentrations of 4-6 ppbv in rural areas and 6-15 ppbv in urban locations, reaching a maximum enhancement of 30 ppbv in eastern Asia. Moreover, NO^sub 2^ enhancements are minor (