Abundance of volatile organic compounds and their role in ozone pollution management: Evidence from multi-platform observations and model representation during the 2021-2022 field campaign in Hong Kong

Volatile organic compounds (VOCs) are a diverse group of species that contribute to ozone formation. However, our understanding of VOC dynamics and their effect on ozone pollution is limited by the lack of long-term, continuous, and speciated measurements, especially of oxygenated compounds. To address this gap, this study integrates on-land, shipborne, and spaceborne measurements from a field campaign in Hong Kong during 2021-2022, analyzing 45-98 VOC species over land and water. Results show that oxygenated VOCs (OVOCs) account for 73 % (37 ppbv) of the total VOC concentration and 56 % of the total ozone formation potential (OFP), underscoring their indispensable role in VOC chemistry. Despite such importance, OVOCs are underestimated by 45 %-70 % in the CMAQ model, while non-methane hydrocarbons (NMHCs) face a lesser underestimation of 47 %-48 % (i.e., "model underestimation"). Meanwhile, the model does not currently account for 17-56 species of the total measured VOCs (i.e., "model omission"). According to this, we break down the observed overwater VOC concentration of 51 ppbv into three components: 9 ppbv (18 %) successfully represented, 35 ppbv (69 %) underestimated, and 7 ppbv (14 %) omitted in the model. For OFP, the breakdown shows 26 % successful representation, 54 % underestimation, and 20 % omission. Together, both "omission"and "underestimation"reveal the overall "VOC underrepresentation"in the model, which partly results in greater ozone sensitivity to VOCs than observed by spaceborne TROPOspheric Monitoring Instrument (TROPOMI) in polluted areas. The findings provide valuable insights into regional pollution dynamics, and inform VOC-related model development and air quality management.