OH in the TWP: An In-Depth Comparison of CONTRAST and CAM-Chem OH Precursors and Implications for the Oxidative Capacity of the Troposphere

JULIE M. NICELY; DANIEL C. ANDERSON; TIMOTHY CANTY; ROSS SALAWITCH; RAFAEL PEDRO FERNÁNDEZ; ALFONSO SAIZ-LOPEZ; CONTRAST SCIENCE TEAM

Boulder

Workshop; Composition and Transport in the Tropical Troposphere and Lower Stratosphere Meeting (CT3LS-2015); 2015

National Oceanic and Atmospheric Administration

p { margin-bottom: 0.1in; line-height: 120%; }Hydroxyl radical(OH) is the main daytime oxidant in the troposphere and determinesthe atmospheric lifetimes of many compounds of interest. It has beenhypothesized that a region of very low OH in the tropical westernPacific Ocean allows otherwise short-lived compounds (includingbiogenic ozone depleting substances) to be transported intact to theUTLS by deep convection. We use the complete, updated measurementsfrom the CONTRAST field campaign in the tropical western Pacific toconstrain the box model DSMACC and estimate OH concentrationsencountered in the mif- to upper‐troposphere of this region. Measurements reveal a background, unpolluted state of thetroposphere, with pervasive high O3 /low H2 O filamentarystructures present in the mid‐troposphere. We examine the impactsof these distinct air parcels on OH as well as the global modelCAM‐Chem's ability to reproduce these conditions. The effects ofOH precursor differences between observations and CAM-Chem on theoxidative capacity of the troposphere are further investigated usingthe box model.