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

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.

Estimating Visible Band Albedo from Aerial Orthophotographs in Urban Areas

“…The methodology described above was applied to the data representing the inner city of Košice. The DSM and orthophotographs were prepared during our previous studies [14][15][16]. All calculation steps were completed in GRASS GIS.…”

“…The solar altitude was 57.15 • and solar azimuth 183.54 • measured from North clockwise. The vector-based land cover map was derived from the orthophotomosaic consisting of 23 land cover classes typical for this urban area [15]. The dominating land cover classes were roofs (27.84% of the total area), asphalt roads (25.67%), grass (20.44%) and trees (16.86%).…”

“…The growing interest in environmental and sustainable energy problems specifically related to urban areas such as UHI phenomenon or solar energy applications stimulates the development of simulation models requiring high-resolution geospatial data including albedo [14,15]. Albedo is an important input parameter in solar radiation and land surface temperature (LST) models.…”

Assessing Land Surface Temperature in Urban Areas Using Open-Source Geospatial Tools

“…As shown by Hofierka et al (2020b), these calculations can be efficiently used in estimation of LST assuming the absorbed solar radiation is directly converted to LST using the Stefan-Boltzmann Law. This solution also requires a DSM representing a land surface morphology, spatially distributed data representing thermal properties of land surfaces and concrete meteorological conditions (Hofierka et al, 2020a(Hofierka et al, , 2020bKolečanský et al, 2021). This LST model is implemented in GRASS GIS as a LST module written using a script (shellscript, Python).…”

“…Using this script, the r.sun solar radiation model in GRASS GIS is used to calculate the effective solar irradiance for selected time horizons during the day. The solar irradiance calculation can account for an attenuation of beam solar irradiance by clouds estimated by field measurements (Hofierka et al, 2020a). The proposed LST model also accounts for a heat storage in urban structures depending on their thermal properties and geometric configuration.…”