2023 Volume 58 Issue 1 Pages 35-45
Tropospheric ozone has been the focus of attention as an air pollutant of concern for its effects on health and vegetation and also a short-lived climate forcer (SLCF) along with methane and black carbon (BC). Since ozone is secondarily produced through tropospheric photochemistry, a sophisticated chemical model covering the HOx cycle reaction mechanism is necessary for impact assessment and future predictions. The HOx cycle includes two processes that are considered to be potential sources of error. One is the heterogeneous uptake process of peroxy radicals (HO2 and RO2) onto clouds and aerosols, and the other is the reaction of OH radicals with unidentified and/or difficult-to-measure reactive species. In both cases, the evaluation of ozone production can change by several tens of percent with or without consideration, and their incorporation into atmospheric chemistry models remains a challenge. The author has quantitatively verified the suppression of ozone formation by aerosols by determining the uptake coefficient of peroxy radicals using a laser spectroscopy-based HOx reactivity measurement system, and also investigated the sources of unidentified and difficult-to-measure OH reactive species through atmospheric observations and laboratory experiments. This paper reviews the results of previous research studies of both processes and current understanding.
