Analysis of the air flow performance in Warsaw in years 2002-2016

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Nowadays, more than s half of the world’s population lives in urban areas. By 2045 this number is expected to surpass six billion, reaching 66 percent by 2050 (United Nations, 2014). People decide to choose cities as their living place for various reasons, such as developed labour market or wide range of services. Unfortunately, highly urbanised areas, despite their understandable economic and living- standard advantages, suffer from serious environmental and development problems caused by erroneous planning decisions. City climate is clearly related to general climatic conditions occurring in a selected geographic region, however, it is also dependent on factors such as land use, building geometry or street canyon design. Luke Howard in his renowned work “Climate of London” 200 years ago proved that urban climate differs from the rural one and noticed the urban heat island (UHI) occurrence. Indeed, the city of Warsaw, an object of this study, is distinguished by a lower access of solar power, higher air temperature and shorter period of frost incidence as well as lower relative humidity, bigger cloud cover, higher rates of rainfall and lower wind speed (Stopa-Boryczka, Kopacz-Lembowicz, Wawer, 2001). Rapid changes of temperature, wind and humidity also affect comfort and health of the people as well as energy consumption and air quality (Elliason, 1999). Thus it is important to enable achieving conditions of thermal comfort especially in a hot and humid climate, through increasing wind velocity (Kato & Hiyama, 2012). Ensuring proper airflow in urban areas should be one of the key environmental issues tackled by governments and city mayors. However, T. R. Oke points out that it implies a critical choice between four goals: to maximize shelter for pedestrians by not exposing them to strong winds, to maximize dispersion of pollutants and minimize their impact on inhabitants and vegetation, to maximize urban warmth and to take full advantage of solar energy. We have to take into consideration that large amount of harmful compounds detected in the air of urban areas where human activity is intensified is not only a result of increased emission but also an effect of the strong surface drag in rough structures and limited effectiveness of dispersion of pollutants (Suder & Szymanowski, 2014). Therefore this study was set to analyse changes in morphology and terrain roughness in Warsaw in years 2002-2016 and related changes in city’s aerodynamic properties, including ventilation corridors.
Book of proceedings: Annual AESOP Congress, Spaces of Dialog for Places of Dignity, Lisbon, 11-14th July, 2017
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