Employing an urban meteorological network to monitor air temperature conditions in the ‘local climate zones’ of Szeged, Hungary

Abstract

We analyse the average annual and seasonal air temperature conditions in the ‘local climate zones’ (LCZs) of Szeged, Hungary. The basis of our analysis is a 1‐year dataset from 2014 to 2015 for a 20‐station urban meteorological network. The network and its corresponding LCZ classes put temperature studies in Szeged into a new spatial framework to assess local climate and urban heat island (UHI) conditions. The stations were installed at locally representative sites using a Geographic Information System (GIS) method based on the standard surface parameters of the LCZ classification. The network was purposely designed to monitor thermal differences among LCZ classes in Szeged. We provide detailed site metadata for each of the monitoring stations used in the analysis. Our results show that the densely built‐up LCZ classes have higher annual and monthly mean and minimum air temperatures than structurally open and more vegetated classes, with nocturnal differences of >4 °C observed under calm, clear skies. Among select temperature indices measured in the urban LCZ classes, frost days, cooling degree‐days, and tropical nights differ markedly from the background rural LCZ classes. This difference suggests that local climatologies exist within Szeged, and that these have implications for thermal comfort, urban energy use, and urban agriculture. Finally, the evaluation of heating and cooling rates in Szeged shows an important role for LCZs in UHI analysis.

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“…A similar distribution across LCZs is observed for EAFT and LAFT, except that T2M is approximately 1 K higher during the LAFT for all the LCZs. At NIGHT, both the inter and intra‐LCZ T2M ranges increase, which is consistent with previous findings on more prominent UHIs and larger intra‐LCZ variabilities in cities at night (Alexander and Mills, ; Stewart et al, ; Leconte et al, ; Fenner et al, ; Skarbit et al, ). Generally, the T2M is higher for LCZ 1/2/3, LCZ 4/5, LCZ 6, and LCZ 8 (hereafter “built LCZs”) than for LCZ A, LCZ B, LCZ D, and LCZ G (hereafter “natural LCZs”).…”

“…Large intra‐LCZ variabilities are found for LCZ 6 and LCZ 8, which may be due to the heterogeneity in urban form owing to their locations at urban–rural boundaries, or simply as a result of the large number of data points (Figure ). Interestingly, the large intra‐LCZ variability for LCZ 6 is also observed in Berlin (Germany; Fenner et al, ) and Szeged (Hungary; Skarbit et al, ).…”

“…The nocturnal air temperature difference between LCZ X (where X = 1 to 10) and LCZ D (Δ T X–D ) is often used to quantify the UHI intensity in cities (Alexander and Mills, ; Stewart et al, ; Leconte et al, ; Fenner et al, ; Skarbit et al, ). The mean ΔT2M X–D at NIGHT obtained in this study range from 0.25 K for ΔT2M 9– D to 2.82 K for ΔT2M 1/2/3– D (Table c).…”

“…() have also reported annual variabilities in the inter‐UCZ/LCZ temperature differences, and observation‐based studies generally indicate that cloud‐free days with low wind speeds in the summer favour pronounced temperature differences between LCZs (e.g., Alexander and Mills, ; Lehnert et al, ; Fenner et al, ). Regarding the diurnal variability, the UHI is commonly known as a nocturnal phenomenon (Oke, ; Cleugh and Grimmond, ), which has been confirmed by previous UHI studies using the LCZ concept (Alexander and Mills, ; Leconte et al, ; Fenner et al, ; Skarbit et al, ). During the day, however, the temperature contrast between “urban” and “rural” LCZs becomes less evident, and it may even be reversed owing to shading within compact urban structures (Erell and Williamson, ; Hidalgo et al, ; Houet and Pigeon, ; Middel et al, ); this phenomenon is denoted as an “urban cool island.”…”

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“…Perini and Magliocco [24] testified that higher density caused higher air temperature in Italy. A study conducted in Szeged, Hungary found that densely built-up areas had higher annual and monthly mean and minimum air temperatures than structurally open and more vegetated areas [35]. However, in an experimental study conducted in Hong Kong (a typical compact city), it was found that sites with higher density experienced lower air temperature [36].…”