Modeling Diurnal Changes in Land Surface Temperature in Urban Areas under Cloudy Conditions

Jaroslav Hofierka,Štefan Kolečanský,Jozef Bogľarský,Anastasia Enderova

doi:10.3390/ijgi9090534

Abstract

Land surface temperature (LST) in urban areas is a dynamic phenomenon affected by various factors such as solar irradiance, cloudiness, wind or urban morphology. The problem complexity requires a comprehensive geographic information system (GIS)-based approach. Our solution is based on solar radiation tools, a high-resolution digital surface model of urban areas, spatially distributed data representing thermal properties of urban surfaces and meteorological conditions. The methodology is implemented in GRASS GIS using shell scripts. In these shell scripts, the r.sun solar radiation model was used to calculate the effective solar irradiance for selected time horizons during the day. The calculation accounts for attenuation of beam solar irradiance by clouds estimated by field measurements. The suggested algorithm accounts for heat storage in urban structures depending on their thermal properties and geometric configuration. Computed land surface temperature was validated using field measurements of LST in 10 locations within the study area. The study confirmed the applicability of our approach with an acceptable accuracy expressed by the root mean square error of 3.45 K. The proposed approach has the advantage of providing high spatial detail coupled with the flexibility of GIS to evaluate various geometrical and land surface properties for any daytime horizon.

Highlights

Land surface temperature (LST) is one of key quantities defining the urban heat island (UHI) phenomenon during hot, sunny summer days
LST is considered to be a reliable indicator of the UHI, as there is a strong correlation between LST and near-surface air temperature for the heat radiating from the surface to the atmosphere [4,5,6,7]
We have prepared a dataset consisting of a digital surface models (DSMs) with 0.5 m spatial resolution representing urban structures such as buildings and trees, land cover representing thermal properties of urban surfaces, albedo and meteorological data such as cloudiness, ambient temperatures and wind speed describing the meteorological conditions in the city on 25 June 2020

Summary

Introduction

Land surface temperature (LST) is one of key quantities defining the urban heat island (UHI) phenomenon during hot, sunny summer days. The LST subsequently increases the air temperature depending on various factors such as thermal properties of urban surfaces and wind conditions. LST is a key parameter in the physics of land surface processes, combining surface–atmosphere interactions and energy fluxes between the atmosphere and the ground. Properties of urban materials, in particular, solar reflectance, thermal emissivity, and heat capacity influence the LST and subsequently the development of UHI, as they determine how the solar radiation is reflected, emitted, and absorbed [8,9]. The magnitude and spatial extent of surface UHIs may vary substantially throughout the day or year depending on the radiative and thermal properties of urban surfaces and geometry [3,10]

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