Projection of present and future daily and evening urban heat load patterns

In this modeling study the recent and future daily and evening thermal climate of a Central-European city (Szeged, Hungary) was investigated in terms of heat load modification by applying MUKLIMO_3 model to project daily and evening climate indices. For surface parameterization the Local Climate Zone (LCZ) scheme was used. The investigation encompassed three climatological time periods (1981–2010, 2021–2050 and 2071–2100) and two emission scenarios for future climate (RCP4.5 and RCP8.5). Our results show that highest index values appear in the city centre and stretch to the NW direction (LCZs 2, 3 and 8) and they decrease towards to the vegetated rural surfaces (mainly LCZ D). That is, the values depend on the zone types and there are more days towards to the densely built-up LCZs. Also, a general temporal change can be detected as the index patterns show the substantial increasing tendency for both indices towards the end of this century. This temporal change suggests a two-way conclusion: first, the increasing number of hot days means a strongly deteriorating change of unfavourable thermal conditions, and second, the change in the number of the evening index provides more opportunities for regeneration and leisure-time activities outdoors in the already thermally less stressful evening hours for the urban inhabitants. This study gives very illustrative examples on the expected climate changes during this century and these examples show that there are several sides to these changes in urban environments. Furthermore, they clearly prove that global or regional scale climate predictions without urban climate interactions do not have enough detailed information

Projection of intra-urban modification of night-time climate indices during the 21st century

The present paper evaluates the alteration of certain night-time climate indices namely warm nights (Tmin ≧ 17 °C) and tropical nights (Tmin ≧ 20 °C) during the 21st century in the city of Szeged. This examination was performed within the framework of a project founded by International Visegrad Fund, where the change of more climate indices were examined in several Central European cities. In this study the MUKLIMO_3 microclimatic model was used, which ensured the modelling of the local scale processes in the examined area. In the model for the land use we applied the Local Climate Zone (LCZ) system. In order to analyze longer periods the cuboid method was applied, which is a dynamical-statistical downscaling technique. We calculated the indices for 1981-2010 based on measurements and for 2021-2050 and 2071-2100 from the EURO-CORDEX datasets. In this study we present the results of Representative Concentration Pathways (RCP) scenarios namely RCP 4.5 and RCP 8.5. Our results show that highest values appear in the city centre and the number of the days clearly increases in the 21st century especially according to scenario RCP 8.5. The values depend on the built-up types and there are more days towards to the densely built-up LCZs. Moreover, considering the relative changes of the zones, larger values appear in sparsely built-up zones and natural surfaces

Projected changes in heat load in Carpathian Basin cities during the 21st century

In this study the changes in the nighttime heat load in Carpathian Basin cities during the 21st century were examined. To quantify the heat load, the tropical night climate index was used. The MUKLIMO_3 local scale climate model was used to describe the urban processes and the land use classes were defined by the local climate zones. The expected change was examined over three periods: the 1981–2010 was taken as reference period using the Carpatclim database and the 2021–2050 and 2071–2100 future periods using EURO-CORDEX regional model simulation data for two scenarios (RCP4.5 and RCP8.5). To combine the detailed spatial resolution and the long time series, a downscaling method was applied. Our results show that spectacular changes could be in the number of tropical nights during the 21st century and the increasing effect of the urban landform is obvious. In the near future, a slight increase can be expected in the number of tropical nights, which magnitude varies from city to city and there is no major difference between the scenarios. However, at the end of the century the results of the two scenarios differ: the values can be 15-25 nights in case of RCP4.5 and 30-50 nights in case of RCP8.5. The results show that dwellers could be exposed to high heat load in the future, as the combined effect of climate change and urban climate, thus developing various mitigation and adaptation strategies is crucial

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Numerical modelling for analysis of the effect of different urban green spaces on urban heat load patterns in the present and in the future

This paper focuses on urban green spaces in terms of climate and human thermal comfort containing their effect on heat load mitigation. It incorporates a modelling study in which the role of green spaces was investigated in terms of heat stress modification by applying MUKLIMO_3 model. During the experiment, the thermal effects of dense trees, scattered trees, grasslands and mixed green infrastructure has been investigated in the case of Szeged (Hungary) and assessed using different climate indices. The investigations encompassed 3 climatological time periods (1981-2010, 2021-2050 and 2071-2100) and two emission scenarios for future climate (RCP4.5 and RCP8.5). It was found that urban green spaces (e.g. parks) generally cool the environment, although, the cooling potential of the different green types differs. The highest reduction of heat load was found in the case of large urban parks comprising of dense trees near the downtown. The spatial extension of detected cooling was found small. However, it would increase during the future, especially in the case of grasslands. For urban planners, it is highly recommended to introduce new green sites within a city and to increase the spatial extension of the existing ones to mitigate and adapt to the impacts of climate change in the urban environment.Peer reviewe

Urban heat island patterns and their dynamics based on an urban climate measurement network

In this paper the spatial pattern of Urban Heat Island (UHI) and its dynamical background are analysed. Furthermore, we examined the annual, seasonal and diurnal characteristics of UHI according to the Local Climate Zones (LCZs). The analysis was performed using one year (between June 2014 and May 2015) dataset from the measurement network of Szeged (Hungary). This network consists of 24 stations measuring air temperature and relative humidity. In the installation of the network the representativeness played an important role in order to that the stations represents their LCZs. We examined the thermal reactions during average and ideal conditions using the so-called weather factor. Our results show that the UHI is stronger in the compactly built zones and there are great differences between the zones. The greatest values appear in summer, while the difference is small in winter. The UHI starts to develop at sunset and exists through approximately 9-10 hours and differences are about 2 °C larger in case of ideal days, when the conditions (wind, cloud cover) are appropriate to the strong development of the UHI. The cooling rates show that the first few hours after sunset are determinative for the developing of UHI. In addition, the effect of UHI on annual mean temperature is also significant