Investigating the impact of WRF urban parameterizations on Paris urban climate

This work aims to investigate the impact of urban parameterizations of a numerical model on regional climate. We use the Weather Research and Forecasting model (WRF) to discover how different implementations of the urban environment may impact the regional climate over the Paris region (FR1 NUTS region). Three identical simulations are conducted, differentiating only in the implementation of the city environment: i) without any urban parameterization (control run) ii) with a Building Energy Model (BEM) iii) with a detailed implementation of optical, radiative and building parameters customized over Paris, derived from Earth Observation data. The simulations cover the time period from May to August 2020, including the Paris heatwave in August. The European domain (EURO-CORDEX) is covered with a spatial resolution of 12 Km, while the area over Paris is covered with a spatial resolution of 3 Km. The simulation protocol follows the World Climate Research Program (WCRP)- CORDEX- Flagship Pilot Study (FPS): Urban environment and Regional Climate Change (URB-RCC) as described in Langedijk et al. (2024). Am improved urban parameterization was implemented using input from very high spatial resolution satellite products regarding land cover, roofs, roads, building heights, surface albedo and vegetation. The variables analyzed in this study include temperature (minimum, mean, maximum), precipitation, short- and longwave net radiation budget at the surface, Planetary Boundary Layer heights, turbulent heat fluxes and soil moisture. The differences between the three simulations are analyzed and compared with relevant observations available. First results identify an improvement in the realization of regional climate over Paris, particularly for minimum temperatures, when more sophisticated urban parameterizations are implemented in the numerical model. 
The research project is implemented in the framework of H.F.R.I Call “Basic research Financing” under the National Recovery and Resilience Plan “Greece 2.0” funded by the European Union –NextGenerationEU (H.F.R.I. Project Number: 14696).