Reactive uptake coefficients for N205 determined from aircraftmeasurements during the Second Texas Air Quality Study:Comparison to current model parameterizations

摘要

This paper presents determinations of reactive uptake coefficients for 2O_5, γ(N_2O_5),on aerosols from nighttime aircraft measurements of ozone, nitrogen oxides, and aerosolsurface area on the NOAA P-3 during Second Texas Air Quality Study (TexAQS II).Determinations based on both the steady state approximation for NO_3and N_2O_5and aplume modeling approach yielded γ(N_2O_5) substantially smaller than currentparameterizations used for atmospheric modeling and generally in the range 0.5-6 × 10~(-3).Dependence of γ(N_2O_5) on variables such as relative humidity and aerosol compositionwas not apparent in the determinations, although there was considerable scatter in the data.Determinations were also inconsistent with current parameterizations of the ratecoefficient for homogenous hydrolysis of N_2O_5by water vapor, which may be as much asa factor of 10 too large. Nocturnal halogen activation via conversion of N_2O_5to ClNO_2on chloride aerosol was not determinable from these data, although limits based onlaboratory parameterizations and maximum nonrefractory aerosol chloride content showedthat this chemistry could have been comparable to direct production of HNO_3in somecases.