The evolution of the Parisian urban climate under a changing climate is analyzed from long-term offline numerical integrations including a specific urban parameterization. This system is forced by meteorological conditions based on presentclimate reanalyses , and climate projections provided by global climate model simulations following two emission scenarios (A1B and A2). This study aims at quantifying the impact of climate change on air temperature within the city and in the surroundings. A systematic increase of 2-meter air temperature is found. In average according to the two scenarios, it reaches +2.0/2.4 • C in winter and +3.5/5.0 • C in summer for the minimum and maximum daily temperatures, respectively. During summer, the warming trend is more pronounced in the surrounding countryside than in Paris and suburbs due to the soil dryness. As a result, a substantial decrease of the strong urban heat islands is noted at nighttime, and numerous events with negative urban heat islands appear at daytime. Finally, a 30% decrease of the heating degree days is quantified in winter between present and future climates. Inversely, the summertime cooling degree days significantly increase in future climate whereas they are negligible in present climate. However, in terms of accumulated degree days, the increase of the demand in cooling remains smaller than the decrease of the demand in heating.

Historically, the urban climate and its interaction with regional environment and larger‐scale meteorological phenomena have been studied by comparing weather stations in urban and surrounding rural areas. Nevertheless, spatialized meteorological data are now available with different spatial resolutions, temporal frequencies, and time depths. Here with the Paris area as a case study, three products were selected for their comparable spatial resolution of 1 km, their daily frequency, and a minimum 15‐year time period with substantial common overlap: the MODIS products for land surface temperature (2000–2016), daily maps of minimum and maximum 2‐m air temperatures (2000–2017) based on a statistical method of spatialization, and the COMEPHORE analysis for precipitation (1997–2012). Several spatialized indicators were used to monitor the urban climate and its impact on local climate. The intensity and spatial extent of both the surface urban heat island (SUHI) and the urban heat island of urban canopy layer (UHI), as well as the effect of the city on precipitation, were characterized. Based on these indicators, a climatological study was made for the Paris urban area and its surroundings. The comparison of (S)UHI climatologies showed that both phenomena (qualified by their intensity and spatial extent) have comparable seasonalities and orders of magnitude at night. The maximum intensity is reached in July, with more than 60% of the city affected by high temperatures. However, the phenomena differ during the day: the SUHI is mostly driven by the differences in surface properties between urban and rural environments, whereas the UHI is more influenced by general wind circulation and local atmospheric turbulence. Finally, the COMEPHORE analysis highlighted the influence of the Paris urban area on rainfall. It is observed throughout the year with an excess in daily precipitation of 29% downwind of the city, with some seasonal variability showing a more pronounced effect in summer.

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L'objectif du projet Epicea était double : évaluer la vulnérabilité de Paris à l'évolution du climat et étudier l'influence de l'aménagement urbain sur le climat à l'échelle locale. L'emploi d'une méthodologie novatrice a permis d'affiner les projections climatiques à l'échelle de l'agglomération, concluant à une forte augmentation du nombre de canicules dans l'agglomération parisienne à la fin du XXI e siècle. Des simulations à haute résolution de la canicule de 2003 ont ensuite permis d'identifier les zones les plus vulnérables aux particularités du climat urbain. Enfin, des modifications du climat urbain liées à quelques scénarios d'aménagement élaborés avec la Ville de Paris ont été modélisées.

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