The OH reactivity describes, in large part, the importance of any individual gas-phase species in the daytime oxidative chemistry of the atmosphere. In most locations in the continental boundary layer on Earth, there are significant gaps in our understanding of which species contribute to the total atmospheric OH reactivity. During two research flights over the LA basin and San Joaquin Valley, air samples were taken with the comprehensive suite of instruments in the KORUS-AQ mission payload. These data were used to test our understanding of the OH reactivity budget in locations with distinct sources of atmospheric emissions. A bottom up analysis of OH reactivity was conducted for various regions throughout the two flights in order to gain more information on the key species responsible for the total OH reactivity as measured by the ATHOS instrument. This allowed for the identification of possible missing chemical species not detected by the suite of instruments on board the DC-8. The missing component can be potentially attributed to the breakdown products of oxidized VOCs, which were approximated for in calculations presented here aimed at closing the total OH reactivity gap. These findings present a comprehensive evaluation of the calculated OH reactivity compared to the total measured as well as the spatial variability in these budgets. These findings are useful in understanding the sources of emissions that contribute to the formation of the ozone in the LA basin and San Joaquin Valley.

Presentation Slides: https://www.scribd.com/document/321271518/Total-and-Bottom-Up-OH-Reactivity-Characterization-of-the-LA-Basin-and-San-Joaquin-Valley#fullscreen&from_embed