A standardized Physical Equivalent Temperature urban heat map at 1-m spatial resolution to facilitate climate stress tests in the Netherlands

S Koopmans,B.G Heusinkveld,G.J Steeneveld

doi:10.1016/j.buildenv.2020.106984

Abstract

In the Netherlands, municipalities and other sub-national governments have to conduct climate stress tests to examine the societal impact of heat load by citizens. So far, these parties have been hindered by the abundance of contrasting urban heat maps produced with different metrics and methods by different agencies. To unify the stress tests, we present a methodology for a standardized urban heat map at 1-m spatial resolution by selecting the Physical Equivalent Temperature (PET) as metric for heat stress.First we present an empirical regression model for PET, based on a variety of weather data and street configurations in the human thermal energy balance model Rayman. Thereafter, this empirical PET-model is evaluated for the midsized town Wageningen (the Netherlands). Meteorological observations taken at a nearby reference site and straightforward geographical data have been used as model input. Also, established methods were applied and elaborated to account for the urban heat island effect and wind speed reduction in the city. The presented method is validated against bike traverse observations of PET. Wind speed is the most challenging feature to map, due to its unsteady and local behaviour in cities.As a result, an afternoon averaged PET heat map is demonstrated as standard for an extreme heat day (1:1000 summer half year days), and a cumulative exceedance PET heat map for a representative year. Furthermore, a heat map is projected for 2050 according a warm climate change scenario.

Highlights

Climate change and the urbanization urges authorities to investigate whether climate adaptation measures should be taken [1], via so called climate stress tests in the Netherlands
We present a recipe for a 1-m resolution heat map representing the Physiological Equivalent Temperature (PET) at pedes trian height for current and future climate
As testbed the mid-sized town of Wageningen has been chosen since traverse observations are available for this town

Summary

Introduction

Climate change and the urbanization urges authorities to investigate whether climate adaptation measures should be taken [1], via so called climate stress tests in the Netherlands. This study focuses on heat stress, and develops high-resolution (1 m) heat maps that indicate the hot spots and help decision makers to plan their climate adaptation and infrastructural measures. Many different urban heat maps circulate indicating different heat metrics, which may confuse stakeholders of municipalities and subna tional governments. These metrics may vary from remote sensing based surface temperatures [2], urban heat islands (UHI) based on air tem perature [3], to the number of tropical nights (nights with minimum temperatures above 20 C) [4]. To unify the heat maps the Dutch Min istry of Infrastructure asked a broad consortium to select one heat metric, and to develop a recipe to create an accompanying heat map

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Discussion

Conclusion