Relating urban development and densification to temporary changes in the air temperature in Warsaw (Poland)

The assessment of the influence of urbanisation effects on air temperature trends has been widely discussed in the literature. Urbanisation affects the urban active surface energy balance, resulting in the formation of urban heat island, also observed in the Warsaw conurbation. This article presents the diversity of long-term changes in air temperature at three Warsaw meteorological stations situated in the districts of Ursynow, Okecie and Bielany, and demonstrates changes in thermal conditions during a long-term urbanisation process. Ursynow is the station where the changes of the surrounding area were most significant among the three analysed ones and the rise in the air temperature for this station was the greatest and it was observed from 7.5 °C in the years 1961–1970 to 8.5 °C in the years 2001–2010. The diversity of air temperature between the stations depends on their location. All of them are situated within the conurbation, at some distance from the city centre but the nature of their surroundings is different. The diversity applies to all annual characteristics of air temperature: its mean, mean maximum and mean minimum values.