Improved models, improved information? Exploring how climate change impacts pollen, influenza, and mold in Berlin and its surroundings

Urban decision makers rely on evidence-based climate information tailored to their needs to adequately adapt and prepare for future climate change impacts. Regional climate models, with grid sizes between 50-10 km, are a useful outset to understand potential future climate change impacts in urban regions. The recently developed convection-permitting models have grid sizes less than 5 km, and better resolve smaller scale atmospheric processes such as convection, and its interactions with the land surface, by also better representing complex terrain, for instance cities. This study investigates how the convection-permitting resolution affects the simulation of climate change conditions in the urban-rural context, demonstrated through three impact cases: influenza spread and survival; ragweed pollen dispersion, and in-door mold growth. Simulations by the regional climate model REMO are analyzed for the near future (2041-2050) under emission scenario RCP8.5. Taking the Berlin region as a testbed, the findings show that the change signal reverses for the 3 km compared to the 12.5 km grid resolution for the impact cases pollen, and mold, which indicates an added value. More pollen days are projected in Berlin under future climate conditions. Less mold days can be expected, but longer consecutive periods, under future climate conditions. For influenza, the convection-permitting resolution intensifies the decrease of influenza days, nevertheless longer periods of consecutive influenza days are found under near-term climate change. The results show the potential of convection-permitting simulations to generate improved information about climate change impacts for urban regions to support decision makers, and in order to build the resilient cities of tomorrow.