Using Total Peroxy Radicals to Evaluate Ozone Production in Northern Michigan and San Antonio

Peroxy radicals (HO2 + RO2) are an essential ingredient in tropospheric ozone formation through their reaction with NO. Knowledge of the peroxy radical abundance in a given location is necessary to understand both ozone production rates as well as the ozone production regime (i.e. NOX or VOC limited). Despite their importance, observations of ambient peroxy radicals are limited. Here, we use in situ observations of total peroxy radicals made with an ethane-based chemical amplification system (EChAMP) and concomitant observations of additional trace gases to explore ozone production in multiple chemical environments: a forested region in northern Michigan, dominated by biogenic VOC emissions, and sites in and upwind of San Antonio, Texas, which are affected by a variety of emission sources. These observations will be used to evaluate both the production of ozone in various chemical mechanisms as well as the accuracy of determining the ozone production regime from satellite retrievals of HCHO and NO2.