Radiosity from Individual Urban Landscape Elements Measured Using a Modified Low-Cost Temperature Sensor

Jane Loveday,Gregory M Morrison,Grant K Loveday,Boon-Lay Ong,Joshua J Byrne

doi:10.3390/urbansci4010014

Abstract

Loss of green space in our suburban environment is contributing to increased urban heat. The material properties of surface treatments or landscape elements (LEs) are a determining factor in the amount, timing, and type of radiation present in the local environment. Landscape designers can use this information to better design for urban heat management, as emitted and reflected radiation (radiosity) from LEs can affect pedestrians via heat stress and glare and affect energy usage in buildings and houses if the landscape sky view factor is low. Low-cost black painted iButton temperature sensors were successfully used as radiometers to concurrently measure the daytime radiosity from 19 LEs samples located on an oval in the warm temperate climate of Perth, (Australia). Normalisation against gloss white paint on polystyrene removed the effect of varying weather conditions. Each LE had the same normalised average radiosity (DRav) between seasons (within ±5%), meaning the relative radiosity of new LEs can be measured on any day. White and lighter coloured LEs had the highest DRav and would have the most detrimental effect on nearby objects. Plants and moist LEs had the least DRav and would be most beneficial for managing local daytime urban heat. Measuring relative radiosity with iButtons presents a new way to examine the effect of LEs on the urban environment.

Highlights

The urban heat island (UHI) effect is the increased night−time ambient temperatures in urban areas when compared with nearby rural areas [1]
Using samples of landscape elements (LEs) is beneficial, as they can be placed in an open area with a high sky view factor (SVF) [42] in order to minimise the radiative interference from surrounding objects
These results indicate that there is some overlap in the ranking order of the LEs in Table 7, in the mid-range of relative radiosities

Summary

Introduction

The urban heat island (UHI) effect is the increased night−time ambient temperatures in urban areas when compared with nearby rural areas [1]. Superimposed on this are the increasing ambient temperatures due to global warming, causing particular concern in urban areas. Landscapes can consist of a number of different individual surface treatments defined here as landscape elements (LEs), such as turf grass, concrete paving, crushed rock, mulch, trees, and shrubs. The amount and timing of urban heat is influenced by the material properties of these LEs, in particular albedo, moisture availability, surface roughness, and thermal inertia [1,6].

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