A new method for fine-scale assessments of the average urban Heat island over large areas and the effectiveness of nature-based solutions

Dirk Lauwaet,Roy Remme,Steven Broekx,Wouter Lefebvre,Hans Hooyberghs,Inge Liekens,Ton De Nijs,Koen De Ridder,Els Verachtert

doi:10.3897/oneeco.3.e24880

Abstract

People living in cities experience extra heat stress due to the so-called Urban Heat Island (UHI) effect. To gain an insight into the spatial variability of the UHI for the Netherlands, a detailed map (10 m horizontal resolution) has been calculated that shows the summer-averaged daily maximal UHI situation. The map is based on a relationship between the UHI, mean wind speed at 10 m height and the number of people living within a distance of 10 km, derived from simulations of over 100 European cities with the extensively validated urban climate model UrbClim. The cooling effect of green and blue infrastructure is also taken into account in the map, based on these simulation results. The presented map will help local authorities in defining target areas for climate adaptation measures and estimate the impact of nature-based solutions.

Highlights

High population density and rapid urban growth increase the vulnerability of cities to extreme weather (Rosenzweig et al 2015)
We present a GIS-based methodology that combines both the advantages of physically based model results with the fast and simple regression methodology to deliver a very high resolution (10 m) daily maximal urban heat island (UHI) map in which the effectiveness of existing green and blue infrastructure can be assessed for all locations
A statistical analysis of the simulation results revealed that the summer (June-August) average daily maximal UHI value of a given city can be estimated based on only two explanatory variables: the mean wind speed at 10 m height and the total number of people living within a radius of 10 km (Fig. 1)

Summary

Introduction

High population density and rapid urban growth increase the vulnerability of cities to extreme weather (Rosenzweig et al 2015). Heat extremes are amongst the most important weather-related health hazards in cities, where the presence of the urban heat island (UHI) is likely to exacerbate the effects of extreme heat This UHI is caused by the increased heat capacity of cities, anthropogenic heat sources and the imperviousness of urban surfaces, which inhibit evaporative cooling (Oke et al 1991, Lynn et al 2009). Due to the UHI increment, cities are vulnerable to heat waves, with an excess of heat-related mortalities (Gabriel and Endlicher 2011) In this context, nature-based solutions as urban greenery and water features have been proposed as an effective measure to mitigate the UHI and improve the urban microclimate (Demuzere et al 2014, Tan et al 2016). Water features have the potential to alleviate high urban temperatures through enhanced evaporation and reduced sensible heat fluxes (Nishimura et al 1998, Coutts et al 2012)

Methods

Results

Conclusion