Observed and simulated VOC speciation and OH reactivity across diverse chemical environments during the 2024 ASIA‑AQ campaign

Quantifying the abundance of volatile organic compounds (VOCs) and accurate representation of their oxidative processing in air quality models are essential for effective air quality management. The NASA ASIA-AQ (Airborne and Satellite Investigation of Asian Air Quality) campaign, conducted in February–March 2024, represents a collaborative international effort to investigate the drivers of air pollution—both local and transported—across four key regions: South Korea, Philippines, Taiwan, and Thailand. As part of this effort, more than 100 C1–C10 VOCs were measured using a suit of state-of-the-art in-situ instruments such as the NSF NCAR Trace Organic Gas Analyzer equipped with a high-resolution time-of-flight mass spectrometer (TOGA-TOF) and the UC Irvine Whole Air Sampler (WAS), all on-board the NASA DC-8 aircraft during its final mission. Here, we present the measured VOC speciated abundance and OH reactivity (OHR) in these four regions. Thailand, largely affected by regional biomass burning emissions during ASIA-AQ, had the highest VOC loading of all the sampled regions and non-methane VOCs (NMVOCs) contributed to approximately half of its total OHR. We complement the OH reactivity analysis with F0AM box modeling simulations to discuss the contribution of unmeasured species. Our results suggest that non-measured NMVOCs contribute up to 40% of OHR. Furthermore, we compare the OHR calculated results against the MUSICAv0 (Multi-Scale Infrastructure for Chemistry and Aerosols version 0) modeling results. Preliminary results suggest that MUSICAv0 broadly captured the total NMVOC OH reactivity but with differences noted, and that significant model/measurement discrepancies were found for specific compounds and compound classes in some regions. We further expand this analysis and quantify the sensitivity of the modeling results to the chemical mechanism complexity used in the simulations.