Abstract
In cities located in concave landforms, urban heat island (UHI) is an element of a complicated thermal structure and occurs due to the common impact of urban built-up areas and orography-induced processes like katabatic flows or air temperature inversions. Krakow, Poland (760,000 inhabitants) is located in a large valley of the river Vistula. In the years 2009–2013, air temperature was measured with the 5-min sampling resolution at 21 urban and rural points, located in various landforms. Cluster analysis was used to process data for the night-time. Sodar and synoptic data analysis provided results included in the definition of the four types of night-time thermal structure representing the highest and the lowest spatial air temperature variability and two transitional types. In all the types, there are three permanent elements which show the formation of the inversion layer, the cold air reservoir and the UHI peak zone. As the impact of land use and relief on air temperature cannot be separated, a concept of relief-modified UHI (RMUHI) was proposed as an alternative to the traditional UHI approach. It consists of two steps: (1) recognition of the areal thermal structure taking into consideration the city centre as a reference point and (2) calculation of RMUHI intensity separately for each vertical zone.
Highlights
The concept of urban heat island (UHI) has been well known since the nineteenth century; numerous methodological issues are still the subject of discussion
In the case of Kraków, a city located in a large valley, outside mountain areas, the application of the local climate zones (LCZs) and UHI concept is problematic, due to the significant impact of relief-induced mesoclimatic processes on the thermal structure of the study area
Concerning the relief-modified UHI (RMUHI) concept, UHI is first presented as an element of a complex thermal structure influenced by land use/land cover, topographic features and local climate processes forced by the presence of a diversified relief
Summary
The concept of urban heat island (UHI) has been well known since the nineteenth century; numerous methodological issues are still the subject of discussion. It is widely accepted that UHI, i.e. the occurrence of higher air temperature in urbanized areas than in rural areas, is the effect of combined influences mainly of changes to the surface geometry in the built environment due to land use changes and emission of anthropogenic heat. Lowry (1977) claimed that the value of a meteorological element measured in a city consists of three components: general climatic background, impact of local conditions (e.g. landform and land cover) and impact of urban areas. Other approaches comprised either elimination of the landform impact with the use of statistical procedures or emphasized the role of relief in a study as an important factor controlling the local climate. Ketterer and Matzarakis (2014) studied the bioclimate of Stuttgart in relation to UHI and stressed the possible combined impact of orography and land use on the spatial variability of the urban microclimate UHI formation and intensity in cities located in the mountains were studied, e.g. in Switzerland by Roten et al (1984; for Fribourg) and Wanner and Hertig (1984; for Basle, Biel, Berne), in Austria by Lazar and Podesser (1999; for Graz) and Rupnik (2003; for Salzburg) or in Slovenia by Hocevar and Petkovsek (1995; for Ljubljana). Saaroni and Ziv (2010) analysed long-term changes in UHI intensity in Beersheba, Israel, and took into account the impact of topographic parameters on permanent factors controlling the phenomenon. Ketterer and Matzarakis (2014) studied the bioclimate of Stuttgart in relation to UHI and stressed the possible combined impact of orography and land use on the spatial variability of the urban microclimate
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
