Abstract
To study urban heat island (UHI), Landsat 5 TM data and in situ measurements of air temperature from nine points in Poznań (Poland) for the period June 2008–May 2013 were used. Based on data from measurement points located in different types of land use, the surface urban heat island (SUHI) maps were created. All available and quality-controlled Landsat 5 TM images from 15 unique days were used to obtain the characteristics of land surface temperature (LST) and UHI intensity. In addition, spatial analysis of UHI was conducted on the basis of Corine Land Cover 2006 dataset. In situ measurements at a height of 2 m above ground level show that the UHI is a common occurrence in Poznań with a mean annual intensity of 1.0 °C. The UHI intensity is greater during the warm half of the year. Moreover, results based on the remote sensing data and the Corine Land Cover 2006 indicate that the highest value of the mean LST anomalies (3.4 °C) is attained by the continuous urban fabric, while the lowest value occurs within the broad-leaved forests (−3.1 °C). To re-count from LST to the air temperature at a height of 2 m above ground level (Tagl), linear and non-linear regression models were created. For both models, coefficients of determination equal about 0.80, with slightly higher value for the non-linear approach, which was applied to estimate the Tagl spatial variability over the city of Poznań.
Highlights
The phenomenon of an urban heat island (UHI), consisting of a significant increase in urban area’s temperature with respect to the surrounding suburban and rural neighborhoods, has been known and studied since the nineteenth century (Landsberg 1981; Fortuniak and Kłysik 2008)
The intensity of the UHI was in general higher in the spring and summer seasons, even though it must be stated that extreme values may occur throughout the Figure 3 shows the diurnal and annual UHI intensity in all the city’s studied points
In situ measurements clearly show that the UHI phenomenon is a common occurrence in the city of Poznań (Półrolniczak et al 2015)
Summary
The phenomenon of an urban heat island (UHI), consisting of a significant increase in urban area’s temperature with respect to the surrounding suburban and rural neighborhoods, has been known and studied since the nineteenth century (Landsberg 1981; Fortuniak and Kłysik 2008). Oke (1979) determined that UHI (or atmospheric UHI) can be defined for the urban canopy layer (UCL) and urban boundary layer (UBL). The UCL observations contain in situ measurements or data from sensors mounted on mobile platforms (using cars and bicycles). The UCL consists of air volume which is contained between urban buildings and other rough elements. In the case of UBL (i.e., a layer above UCL), the data comes from instruments mounted on special platforms, balloons, or aircraft (Voogt and Oke 2003). The UBL becomes part of the planetary boundary layer whose characteristics are modified by the actual presence of an urban area as its lower boundary (Oke 1976)
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