The impact of urban policy scenarios on local climate: a multi-model intercomparison

Understanding the impact of urban environments on the local climate has been a crucial topic in recent years. Changes in the cities structure are expected due to the ongoing urbanization trends and climate-aware mitigation planning. These policy implementations are expected to affect the local urban surface and its interaction with the climate system. Here, we are interested in investigating these impacts coupled to a heatwave condition, due to its adverse impact on human health. In the presented work, we investigate the multi-model response to different urbanization and urban greening scenarios. We employ two NWP models at the 2.1 km convection-permitting resolution: ICON-LAM (ICOsahedral Nonhydrostatic Model in Limited Area Mode) and WRF-ARW (Weather Research and Forecasting Model). Our one-month experiments comprise the 2019 ``record-breaking'' heatwave in Western Europe and they are all a downscaling of ICON-EU (6.5km resolution). The urban policy scenarios are built from the CORINE land use dataset and they include two urbanization and two urban greening settings, for each model. Urbanization is represented as a sprawl of the main urban areas within the domain towards the natural surrounding areas. To increase the urban green fraction within the main cities, we increase the number of green areas within each city. Our analysis shows the multi-model comparison of the effects of the mentioned urban policies on the urban heat island (UHI) under heatwave conditions. Further, we quantify the effects of urban greening as an efficient tool to mitigate expected climate impacts in terms of the Discomfort Index, and not just for the UHI.Further, we evaluate the similarities and dissimilarities between the two models in terms of multiple correlation decomposition accordingly to Glowienka-Hense et al. 2020.