High-resolution modelling of park cooling efficiency during summer in Paris

Heat waves pose a significant risk to human health, particularly pronounced in urban areas due to the urban heat island (UHI) effect. Understanding the varying impacts of heat waves across different neighbourhoods within cities is vital, as well as recognizing the potential of urban vegetation in mitigating temperatures. The Heat and Health in Cities (H2C) project aims to enhance urban climate services to support proactive measures and policies addressing extreme heat risks in cities, with a specific focus on the Paris region. Employing a multi-source observational approach alongside numerical models, the project seeks to provide a more comprehensive assessment of environmental conditions, ranging from regional to neighbourhood scales. 

The main aim of this study is to examine the efficiency of parks and urban forests in mitigating air temperatures during summer periods including heat waves. Using the Meso-NH model, this study conducts simulations of discrete events occurring in 2022 and 2023 within Paris and the Ile-de-France region. Meso-NH, a non-hydrostatic research atmospheric model, is driven by atmospheric boundary conditions from the French convective-scale operational Numerical Weather Prediction model AROME-France. Coupled with Meso-NH is the land surface model SURFace EXternalized (SURFEX), incorporating the Town Energy Balance (TEB) model for urban elements combined with a high-resolution surface database. Simulations are based on three nested domains with respective grid resolutions of 1200 m, 300 m (over Paris region), and 100 m (over the city of Paris). Model validation of 2-m air temperatures is performed using data from the PANAME (PAris region urbaN Atmospheric observations and models for Multidisciplinary rEsearch, https://paname.aeris-data.fr/) intensive measurement campaign. 

Previous works have established through the local observations the existence of weather types with contrasting UHI regimes resulting in distinct park cooling efficiencies. The aim of this study is to determine whether hectometric-scale modelling is able to replicate these observed results. The challenge is then to be able with modelling to study and better understand the microclimatic contrasts within the city, in particular the cooling effects generated by urban parks of various sizes and the factors contributing to their variability.