Microclimatic factors in urban development: The setup of an environmental observatory at the FAD STU

Tomáš Hubinský, Ján Legény

SUMMARY

The presented research focuses on energy (im)balance on both global and local scale. Since the second half of the twentieth century, research regarding cities and their climate has focused on various physical properties that affect various physical and chemical processes such as energy absorptivity, reflectivity, emissivity, thermal conductivity, transpiration, evaporation, evapotranspiration, photosynthesis, etc. With respect to meteorology, physical processes that occur on a local scale in the atmosphere near the ground, on the land surface, and in the soil are generally termed microclimatic processes. Due to the long-term consolidation of interactions between microclimatic processes and the relatively low rate of emerging climatic disruptions, microclimatic conditions in natural environment are rather stable and predictable in time (short / long periods) with a high degree of accuracy. In the era of the Anthropocene epoch characterized by human activities with dominant influence on disruptions in the natural flow of energy and matter, the climate has become highly unpredictable on all spatial-temporal scales. Thus, urban climate is one of the most evident examples of inadvertent climate modification caused by humans. Human activities are therefore considered the dominant microclimatic processes within the city and directly linked to microclimate changes. The main emphasis is placed on microclimatic factors directly affecting public urban spaces and related physical processes regarding the city that are closely linked to energy flows and result in the formation of the Urban Heat Islands (UHIs). As they are one of the main adverse effects of human activities, the paper introduces the classification of UHIs by types, describes the basic differences between the surface energy balance of rural and urban areas, and introduces climate-sensitive urban design as one of the possible ways to mitigate the undesirable anthropogenic impacts on climate change. The authors of the article present their own research, which predominantly focuses on the development of an environmental observatory situated on the rooftop of the building of the Faculty of Architecture and Design STU in Bratislava (FAD STU). They interpret the experimental operation of sensing probe 1 and the first results and measurement data on Global Horizontal Solar Irradiation (GHSI) and their post-processing. In addition, they describe the construction of sensing probe 2, which will provide more data on total atmospheric precipitation, wind speed and its direction, presence of dust particles and carbon dioxide in the air, or spectral characteristics of incident and reflected solar radiation. Finally, the experimental operation of the thermal and micro-camera with fisheye lenses is described. These cameras are essential for measuring the Normalized Difference Vegetation Index (NDVI) as one of the parameters used for the assessment of vegetation vitality, which also plays a key role in the formation of the UHI effect. The creation of an environmental observatory on the grounds of the FAD STU whose operation was experimentally verified by sensing probe 1, along with the future location of sensing probes 2 in selected public urban spaces creates a prerequisite for conducting further research in the field of microclimatic factors affecting urban development. Compared to basic research, the level to which knowledge is implemented in practice in the field of urban microclimate is deficient. Advances in data science have made it possible to process a large number of data (Big Data) using the statistical analysis methods, and thus to gain relevant sources of information that complement the existing ground-based and remote sensing infrastructure. The increasing quality of data, their spatial-temporal density, and shorter response time, with the expected accompanying refinement of forecasting models, improved crisis management, and provision of tools for the retrospective assessment of environmental strategies within the city. The main objective of Climate-sensitive Urban Design (CSUD) is a city that uses resources efficiently in terms of sustainability in order to protect its residents and traffic from severe weather phenomena. The current research conducted at the FAD STU aims to contribute to these sustainable strategies and city management. There are still some specific issues that researchers should address. The first is the development and creation of data prediction models, where the current trend is to increase the complexity of the evaluated microclimatic factors in spatial-temporal detail. Such predictive models and simulations help architects and urban planners understand the interaction of microclimatic factors with the surroundings and allow them to verify the expected benefits of solutions during the design phase. The second is the critical retrospective evaluation of implemented solutions exposed to real conditions not only at the level of architectural and urban design, but also regarding engineering and technical solutions, such as the material composition of surfaces. This approach supports the continuation of the evolution of engineering design. The third is to increase the use of quantifiable parameters to rate the impact of individual and interacting microclimatic factors and to facilitate complex decision-making within the design process.

Keywords: FAD STU, city, urban heat island, urban microclimate, physical parameters, environmental observatory, sensing probe