Local Climate Classification and Dublin’s Urban Heat Island

Paul Alexander,Gerald Mills

doi:10.3390/atmos5040755

Paul Alexander, Gerald Mills

Open Access

https://doi.org/10.3390/atmos5040755

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Abstract

A recent re-evaluation of urban heat island (UHI) studies has suggested that the urban effect may be expressed more meaningfully as a difference between Local Climate Zones (LCZ), defined as areas with characteristic dimensions of between one and several kilometers that have distinct effects on climate at both micro-and local-scales (city streets to neighborhoods), rather than adopting the traditional method of comparing urban and rural air temperatures. This paper reports on a UHI study in Dublin (Ireland) which maps the urban area into LCZ and uses these as a basis for carrying out a UHI study. The LCZ map for Dublin is derived using a widely available land use/cover map as a basis. A small network of in-situ stations is deployed into different LCZ across Dublin and additional mobile temperature traverses carried out to examine the thermal characteristics of LCZ following mixed weather during a 1 week period in August 2010. The results show LCZ with high impervious/building coverage were on average >4 °C warmer at night than LCZ with high pervious/vegetated coverage during conditions conducive to strong UHI development. The distinction in mean LCZ nocturnal temperature allows for the generation of a heat map across the entire urban area.

Highlights

Cities represent the most significant human environments, both in terms of the physical artefacts and socio-economic activities associated with the processes of urbanization
The most commonly studied urban heat island (UHI) is the near-surface air temperature found below roof level within the urban canopy layer (UCL) [1]
This paper reports on a UHI study in Dublin, Ireland conducted during the summer 2010, which used the Local Climate Zones (LCZ) system to structure the observations and interpret the results

Summary

Introduction

Cities represent the most significant human environments, both in terms of the physical artefacts and socio-economic activities associated with the processes of urbanization. The physical presence of cities alters the radiative, aerodynamic, thermal and moisture properties of the atmosphere in and around urban areas. The most pronounced effect detectable is that of positive thermal anomalies associated with nocturnal urban air temperature. The most commonly studied UHI is the near-surface air temperature found below roof level within the urban canopy layer (UCL) [1]. As this is where humans live and work the magnitude of the UHI is directly relevant to studies of human health and comfort and building energy management

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