New Insights Into HOx Chemistry from Aura MLS, Balloon, and Ground Based Observations

Global, space based observations of OH and HO2 (HOx) are available from the Aura MLS instrument since soon after its launch on July 15, 2004, providing a unique opportunity to test our understanding of the photochemical processes that regulate HOx. This presentation will describe validation of the OH and HO2 profiles using balloon-borne measurements of these species from the FIRS-2 and BOH instruments (obtained Sept 2004 at 34N) as well as ground based observations of column OH from the FTUVS (34.4N) and PEPSIOS (34N) instruments. We also present a comparison of measured and modeled profiles of OH and HO2, using a photochemical model constrained by MLS and balloon observations of HOx precursors. Within measured uncertainty, we find good agreement between the observed OH profiles from 30 to 60 km. In contrast to many previous studies, no adjustment to rate constants is needed for agreement between modeled and measured OH profiles. The MLS and FIRS-2 HO2 profiles agree within 25%. We will also analyze daily and seasonal variations in the OH columns through comparison of the ground based observations, model results, and integrated columns from MLS, FIRS-2, and BOH.