01112020 The urban heat island UHI effect and

01/11/2020 The urban heat island (UHI) effect and its sensitivity to large-scale atmospheric flow Koen De Ridder

The UHI phenomenon » urban-to-rural temperature excess » most intense during the evening and early night » causes: » » » low albedo large thermal inertia limited water availability poor thermal exchange anthropogenic heating … 01/11/2020 © 2012, VITO NV 2

Why it is important Health Energy “The evidence that heat waves can result in both increased deaths and illness is substantial, and concern over this issue is rising because of climate change” Reid CE, O’Neill MS, Gronlund CJ, Brines SJ, Brown DG, Diez-Roux AV, et al. 2009. Mapping Community Determinants of Heat Vulnerability. Environ Health Perspect 117: 1730 -1736. Sailor, D. J. 2002. Urban Heat Islands, Opportunities and Challenges for Mitigation and Adaptation. Sample Electric Load Data for New Orleans, LA (NOPSI, 1995). North American Urban Heat Island Summit. Toronto, Canada. 1 -4 May 2002. Data courtesy Entergy Corporation. 01/11/2020 © 2012, VITO NV 3

VITO’s urban climate model (Urb. Clim) LAICa urbanized surface energy balance model 01/11/2020 ©

Urb. Clim features » nested in output of global- or regional-scale models in such a way that it stays close to the large-scale atmospheric fields (Urb. Clim calculates an urban increment) » employs generic data sets for Europe (CORINE land cover, satellite vegetation index, …) » operates at a relatively high spatial resolution of 250 m, accounts for urban canopy layer effects » is very fast – typically a simulation for a 120 20 domain at 250 m resolution takes 48 hours for a Summer season (May-September) 01/11/2020 © 2012, VITO NV 5

Mean 22: 00 UHI intensity Ghent, August 2012 temperature ranges from 0°C (dark blue)

UHI intensity Paris (May-Sep 2003, 22: 00 UT) temperature ranges from 0°C (dark blue)

UHI versus city size 01/11/2020 © 2012, VITO NV 8

UHI intensity Ghent (Aug 2012) RMSE ~ 1. 0°C BIAS ~ 0. 2°C CORR

city selection CMIP 5 socio-economic observations Urb. Clim UHI prediction health effects heat stress

Service aspects – users now time retrospective (~ 10 years) short-term forecast (~ days) medium-to-far future (~ 2030 -2100) seasonal-decadal predictions urban administrations (environment, …) hospitals civil protection energy providers 01/11/2020 © 2012, VITO NV ? urban planners climate adaptation 12