Study of the urban effect of Paris on several thunderstorm cases in 2022, using hectometric ensemble simulations

Climate change and a rapidly increasing urban population make cities more vulnerable to hazardous weather events. The need for a better understanding of meteorological processes and an improvement of the weather prediction system in an urban environment is crucial to mitigate these impacts and protect the population. 

The “Paris Olympics” international Research and Demonstration Project, endorsed by WMO, aims at improving meteorological research in urban meteorological processes and weather forecasting systems at 100m resolution. It mainly focuses on extreme weather events in urban areas such as urban heat islands and thunderstorms. Several study cases have been proposed. They are golden cases observed during the PANAME2022 field campaign in Paris and they represent interesting weather situations to test numerical weather prediction capacities.

The objective of this study is to investigate through the selected cases, the influence of Paris’s urban environment on thunderstorms. An ensemble of hectometric simulations is built using the Meso-NH research atmospheric model initialized and forced by the members of the AROME-EPS ensemble prediction system which has a 1.3 km horizontal resolution. For each case, two sets of ensemble simulations are performed; to identify the main processes driving the interactions between urban environment and thunderstorms: one with a fine-scale surface description of the city (using a multi-layer urban scheme) and another one where the urban surface is replaced with vegetation.

The first results show that it remains challenging to correctly simulate the location of thunderstorms. Nevertheless, the ensemble technique combined with urban and non-urban city description is effective to discriminate random effects from real trends on  the urban environment impacts on thunderstorms.