Evolution of the Parisian urban climate under a global changing climate

Abstract

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.

Characterization of Urban Heat and Exacerbation: Development of a Heat Island Index for California

“…Thus if warmer weather increases the UHI, then mitigation measures such as cool cities will become more important in the future [53], when heat waves are expected to occur more frequently. On the other hand, some studies suggest that UHIs could decrease with higher background temperatures in the long term [54]. Thus, again, this highlights the region-specific nature of urban climates and heat-island responses to changes in background weather and synoptic conditions.…”

Benefits of explicit urban parameterization in regional climate modeling to study climate and city interactions

“…Früh et al (2011) and Lemonsu et al (2013) assessed this way the future climate of Frankfurt (Germany) and Paris (France) respectively, with offline simulations of urban climate forced by statistically or dynamically downscaled GCMs and RCMs. Nonetheless, the surface energy budget and turbulence generated by urban covers may impact the atmospheric characteristics, and these properties may be transported horizontally by advection.…”

Detailed Urban Heat Island Projections for Cities Worldwide: Dynamical Downscaling CMIP5 Global Climate Models

“…McCarthy et al [8] also obtained rather constant, although not static, UHI values for the cities in the United Kingdom under climate change conditions in their regional climate model simulations. Lemonsu et al [11] and Hamdi et al [7] reported a relatively strong decrease in the night-time UHI intensities of Paris (−1 °C) and Brussels (−0.36 °C), respectively. They could attribute these changes to a large reduction of the summer rainfall amounts by the end of the century in their simulations, strongly diminishing the evaporation from vegetation and soils in the rural areas, which gives rise to higher rural temperatures and, hence, a smaller UHI.…”

“…Since mesoscale models become exceedingly slow because of numerical stability constraints when going towards kilometer-scale resolutions, long model integrations are difficult to achieve. Some authors propose alternative methods to project the global climate at the regional scale with dynamical and statistical techniques and then simulating the local scale with an offline urban model or boundary layer scheme with a resolution of 1 km [7,11].…”