Abstract
Heat periods in summer occurred more frequently in this decade and affected the well-being of citizens in several ways. One effect of heat-periods is a higher photochemical ozone production rate, which leads to higher ozone concentrations. Strategies to influence urban climate and air pollution more often include urban green infrastructures (UGI), which are also applied to lower the urban carbon footprint. A side effect of UGI is the emission of biogenic VOCs (BVOCs) such as isoprene, terpenes and oxygenates, which are participating in urban ozone production. In this study, we investigate the effect of UGI BVOCs during heat-period conditions on ozone formation using an integrated urban-scale biogenic emissions and chemistry transport model chain. Therefore, we integrated modelling of BVOC emissions in the EPISODE-CityChem model based on high resolution land-cover and vegetation maps, emission factors for vegetation species, and algorithms to account for meteorological dependencies, e.g. radiation, temperature and humidity. The resulting European plant-specific emission inventory for isoprene, monoterpenes, sesquiterpenes and oxygenated VOC has a spatial resolution of 100m and is applied in the EPISODE-CityChem model with the same resolution. The focus of EPISODE-CityChem is the simulation of complex atmospheric chemistry involved in the photochemical production of ozone in urban areas and accurate representation of dispersion in proximity of emission sources. We performed simulations in the densely populated Rhein-Ruhr area (DE) under heat-period conditions to identify the impact BVOC emissions on ozone formation. The relevance of biogenic emissions is expected to increase in future due to higher frequency of heat-period events related to climate change and due to the decreasing trend of anthropogenic emissions in response to current legislation. Therefore, the established model chain can be a valuable tool for urban planning in view of finding trade-offs between lowering the urban carbon footprint, regulating urban climate, and reduce urban air pollution.
