Photochemical Analysis of ARCTAS Observations

Airborne measurements of several tropospheric species obtained during ARCTAS provide the opportunity to examine the chemistry of the Arctic and to assess the influence of transport from middle latitudes on the polar environment. To better understand Arctic tropospheric chemistry, the consistency between the measurements of radical species and their products is evaluated using a photochemical box model based on current theory and constrained by observed precursors. Comparison with model predictions suggests that observations of HOx and peroxides cannot be reconciled using current theory, and measurements of formaldehyde concentrations are consistently higher than predicted values by nearly a factor of two in the spring phase and by 25% in the summer phase. We present an analysis of the coupled HOx/peroxide/formaldehyde chemistry in the polar troposphere and the sensitivity of modeling this system to assumptions about physical losses to the surface and/or rainout.