Modelling studies of NO3 nighttime chemistry and its effects on subsequent ozone formation

A photochemical box model (NITE-UP) supplied with an updated and additional daytime and nighttime chemical scheme, has been applied to nighttime emissions from a major city (London). Studies have been made of the importance of the temperature-dependent rate constant of the homogeneous and heterogeneous reaction N2O5 + H2O → 2HNO3 on NO3 radicals production. The involvement of the nitrate radical in the nighttime tropospheric chemistry and its influences on the concentrations of other species including N2O5, HNO3, OH, HO2, as well as on the subsequent ozone formation have been modelled for the area downwind of London, under summertime and springtime conditions. The significance of the representation of the NO3 chemistry in computational photochemical models is discussed.