Aude Lemonsu 1, Vincent Viguié 2, Maxime Daniel 1, Valéry Masson 1

Transcription

1 Vulnerability of the city of Paris (France) to future heat waves: Impact of urban sprawl scenarios Aude Lemonsu 1, Vincent Viguié 2, Maxime Daniel 1, Valéry Masson 1 1 Météo-France / CNRS, Toulouse, France 2 Centre International de Recherche sur l Environnement et le Développement, Nogent sur Marne, France Toulouse France

2 Context and motivations extra deaths in France during 2003 heat wave 8,5% of excess mortality in Paris (= 3,7% of French population) Intensification of urban heat island and aggravation of health impacts UHI during a typical summer ΔT = 4 C UHI during 2003 heat wave ΔT = 8 C Paris Paris Toulouse France 2

3 Context and motivations In the future, heat waves will be more frequent, longer and more intense In 2100, Paris will be affected each year, on average, by: heat wave - 11 heat-wave days Maximum intensity ( C C) Projection of future heat waves over Paris region (A1B scenario) Lemonsu et al. 2014, Climate Research Heat-wave duration (days) Toulouse France 3

4 Context and motivations In the future, heat waves will be more frequent, longer and more intense In 2100, Paris will be affected each year, on average, by: heat wave - 11 heat-wave days Maximum intensity ( C C) Projection of future heat waves over Paris region (A1B scenario) Lemonsu et al. 2014, Climate Research Heat-wave duration (days) Toulouse France 4

5 Context and motivations In the future, heat waves will be more frequent, longer and more intense In 2100, Paris will be affected each year, on average, by: heat wave - 11 heat-wave days Maximum intensity ( C C) Projection of future heat waves over Paris region (A1B scenario) Lemonsu et al. 2014, Climate Research Heat-wave duration (days) Toulouse France 5

6 Objectives Study the interactions between climate change, urban climate, and urban expansion ANR VMCS 2008 Evaluate and compare different urban planning policies - Focus on heat wave conditions - Paris (France) as case study as time period of analysis Toulouse France 6 Urban areas Wooded areas Agricultural areas 30 km

7 Systemic modeling methodology Future heatwaves Urban expansion modeling with NEDUM-2D Urban climate modeling with TEB Vulnerability indicators UHI Heat stress Toulouse France 7

8 Long-term scenarios simulated with the land-use transport interaction model NEDUM-2D Macro-scale socio-economic constraints (energy cost, demography trends) Various local-scale urban planning policies SPREAD--OUT CITY SPREAD COMPACT CITY 2550 km² 1900 km² 20th 24th July 2015 Toulouse France GREEN CITY 10/30/50% 2800/3450/4300 km²

9 Physically-based urban canopy model TEB Key physical processes in urban climate development Building energetics Urban green areas Masson 2000 Hamdi and Masson 2008 Bueno et al. 2012; Pigeon et al Lemonsu et al. 2012; de Munck et al Source : APUR 20th 24th July 2015 Toulouse France 9

10 Future heatwaves Characteristics of future heat wavesbased on the RCM projections analysis Lemonsu et al. 2014, Climate Research Number of f heat waves Heat-wave duration (days) Urban climate modelling for heat waves of various intensities and durations representative of future events Toulouse France 10

11 Sensitivity to urban heat island UHI ( C) = Urban Heat Island = T T rural(ref) F UHI (%) = Fraction of city affected by UHI P UHI (%) = Fraction of population affected by UHI Today Paris 7-days heat wave Tmax = 38 C 30 km At night, UHI centered over densely built-up areas At daytime, maximum temperatures over suburbs Toulouse France 11

12 Night Sensitivityof the city to UHI Fraction of city affected 7-days heat wave Tmax = 38 C Day REF SPREAD-OUT COMPACT GREEN 10% GREEN 30% GREEN 50% REF SPREAD-OUT COMPACT GREEN 10% GREEN 30% GREEN 50% At night, urban greening (and less urban compacity) 20 th has 24 th July a positive 2015 effect Toulouse France 12 At daytime, compacity reduces sunshine and warming

13 Sensitivity of city and population to UHI Fraction of city affected 3-21 days heat wave Tmax = 38 C Night Day UHI threshold = 1.5K Fraction of population affected 3-21 days heat wave Tmax = 38 C Heat-wave duration (days) Night Heat-wave duration (days) Day Heat-wave duration (days) Toulouse France 13 Heat-wave duration (days)

14 Sensitivity to urban heat island Outdoor thermal comfort for population Universal thermal climate index (UTCI) Heat stress levels Very strong heat stress Strong heat stress Moderate heat stress No heat stress Toulouse France 14

15 Outdoorheat-stress conditions Number of hours per day spent in strong heat stress (UTCI>32 C) Computed for all modeled heat waves (all intensities/all durations) Weighted according to the occurrence probabilities of heat waves 12 hours / day Population (% %) 14 hours / day 16 hours / day REF Toulouse France 15

16 Outdoorheat-stress conditions Number of hours per day spent in strong heat stress (UTCI>32 C) Computed for all modeled heat waves (all intensities/all durations) Weighted according to the occurrence probabilities of heat waves Population (% %) Heat stress is reduced for less compact and more vegetated cities REF SPREAD-OUT COMPACT GREEN 10% GREEN 30% GREEN 50% Toulouse France 16

17 Conclusions Influence of choice of indicators in the evaluation Max UHI Fraction of city Fraction of population Heat stress Toulouse France 17 Severity COMPACT SPREAD-OUT GREEN 10% GREEN 30% GREEN 50% COMPACT SPREAD-OUT GREEN 10% GREEN 30% GREEN 50% COMPACT SPREAD-OUT GREEN 10% GREEN 30% GREEN 50% COMPACT SPREAD-OUT GREEN 10% GREEN 30% GREEN 50% Densification Densification Densification Densification

18 Conclusions Influence of choice of indicators in the evaluation Interest of multi-criteria and interdisciplinary evaluation Involvement of public stakeholders and urban planners Efficiency of spread-out cities compared to compact city in mitigating UHI and heat stress but increase in CO2 emissions due to transportation Efficiency of greening scenarios but crucial issue of water consumption and water resource management in urban environment Toulouse France 18

19 Thank you for your attention Contact: Lemonsu A., Viguié V., Daniel M., Masson V., 2015: Vulnerability to heat waves: impact of urban expansion scenarios on urban heat island and heat stress in Paris (France), Urban climate, in revision Toulouse France 19