Heterogenous N2O5 uptake during winter: Aircraft measurements during the 2015 WINTER Campaign and critical evaluation of current parameterizations

Formed from the oxidation of nitrogen oxides, N2O5 is heterogeneously lost to aerosol with a highly variable reaction probability, (N2O5), dependent on aerosol composition and ambient conditions. Reaction products include soluble nitrate (HNO3 or NO3-) and nitryl chloride (ClNO2).

We report the first-ever derivations of (N2O5) from ambient wintertime aircraft measurements in the critically important nocturnal residual boundary layer. Box modeling of the 2015 Wintertime INvestigation of Transport, Emissions, and Reactivity (WINTER) campaign over the eastern United States derived 2,876 individual (N2O5) values with a median value of 0.0143 and range of 2x10(-5) to 0.1751. WINTER (N2O5) values exhibited the strongest correlation with aerosol water content, but weak correlations with other variables, such as aerosol nitrate and organics, suggesting a complex, nonlinear dependence on multiple factors, or an additional dependence on a nonobserved factor.