Formaldehyde and hydroperoxide distribution around the Arabian Peninsula – evaluation of EMAC model results with ship-based measurements

Abstract. Formaldehyde (HCHO), hydrogen peroxide (H2O2) and organic hydroperoxides (ROOH) play a key role in atmospheric oxidation processes. They act as sources sinks for HOx radicals (OH + HO2), with OH the primary oxidant that governs self-cleaning capacity. Measurements of these species allow evaluation chemistry-transport models which need to account multifarious source distributions, transport, complex photochemical reaction pathways deposition processes species. HCHO is an intermediate during volatile compounds (VOCs) indicator activity combustion-related emissions. In this study, we use situ observations HCHO, H2O2 ROOH marine boundary layer (MBL) evaluate results general circulation model EMAC (ECHAM5/MESSy2 Atmospheric Chemistry; European Center HAMburg, Modular Earth Submodel System). The dataset was obtained Air Quality Climate Change Arabian Basin (AQABA) ship campaign around Peninsula summer 2017. This region characterized by high levels air pollution, humidity solar irradiation, especially areas Suez Canal Gulf. High pollution up 12 ppbv 2.3 relatively low (≤0.5 ppbv) were detected over We find failed predict absolute mixing ratios high-pollution events Gulf, while it reproduced on average within factor 2. Dry velocities determined at night 0.77±0.29 cm s−1 1.03±0.52 Sea, matched EMAC. budget revealed elevated radical concentrations EMAC, resulted overestimation more than 5 AQABA dataset. underestimated Gulf related EMAC's coarse spatial resolution missing anthropogenic emissions model.