Comparison of surface temperature over different natural and artificial urban surfaces

It is a well-known fact that in urban areas, human activities result in special climatic conditions. Urban climate studies nowadays are becoming more and more important as their results can be directly used by urban planners, architects and municipal decision-makers. In the framework of a long-term cooperation between the Urban Climate Research Group of the Department of Meteorology at the Eötvös Loránd University (Budapest) and the Department of Environment at the Municipality of Újbuda (district XI of Budapest), regular urban climate measurements are carried out in the district XI of Budapest to detect the urban heat island (UHI) effect on different spatial scales.

Measuring campaigns were conducted in summer 2018 and later, in spring, summer and autumn 2019 to determine the surface temperature of various urban materials using a Voltcraft IR-280 infrared thermometer. The purpose of these measurements was to obtain information about the thermal properties of different urban surfaces, objects in order to analyse which surfaces are suitable for decreasing and hence mitigating the UHI effect. The impact of the colour of different surfaces and the role of shading are analysed as well. The measurements were carried out at two measuring sites: (i) in the largest public park of the district, called Bikás Park (with 37 measuring points), (ii) in the commercial and public transportation centre of the district, called Móricz Zsigmond Square (with 17 measuring points). Based on the compiled database, a detailed statistical analysis was performed to investigate the thermal properties of various urban surfaces, e.g. pavements, walls, street furniture, sport facilities, water and plant surfaces.

The results show that the coolest surfaces are natural covers (water, vegetation), while the hottest surfaces are concrete pavements, asphalt and rubber paving when exposed to direct solar radiation. In summer, extremely high surface temperatures can occur, the average surface temperature around noon exceeds 40 °C in the case of dark painted wood objects, asphalt and rubber-paved surfaces with sunny conditions. The analysis focusing on the concrete paving blocks with different colours shows that the average surface temperature of light grey surfaces is 5-7 °C lower than the average temperature of darker colours. During the measurement series, the highest temperatures (over 50 °C) were measured at rubber paving-covered sport facilities and playgrounds, in sunny conditions. This material is very popular because its use has many benefits. Our study shows that the extensive use of these surfaces has a negative impact on the urban climate. These surfaces warm up so much during sunny summer days that the facilities covered with this material become practically unusable due to their extremely hot surface. In the case of this surface material, shading plays an important role as it can effectively control and reduce the warming of rubber paving-covered surfaces.