Deformacja pól zmiennych meteorologicznych przez zabudowę w Warszawie

The paper presents the range of deformation of a field of meteorological variables under the influence of urban development. The threshold values of meteorological factors were defined, in extreme values of differences in thermal conditions between the city and its surroundings. The impact of temperature, cloudiness and wind velocity on the urban heat island was ascertained. The process and rate of heating up and cooling down ofa build up area was investigated. The results of the analysis show that, close up development in the center of Warsaw, deforms most of all the fields of meteorological variables: raises air tempetature, especially the minimal temperature for mean 5-year periods up to 1.9°C, and on individual years up to 2.6°C, and up to 9°C on individual days; reduces daily temperature range up to -2.1°C; reduces relative humidity up to -2%, increasing deficit of air humidity up to 0.4 hPa as well as cloudiness up to 4% and total precipitation up to 6%; reducing mean wind velocity to -1.3m/s. Urban heat island is strongly marked in the summer half-year, when air temperature outside urban area varies between 13° to 16°C. In the winter half year urban heat island is most weakly marked with tempetatures ranging from -2° to 1 °C, and most strongly when temperature drops below - 10°C. The decline of temperature difference between the urban area and its surroundings (ΔT=0) occurs when wind velocity is around 7m/s and cloudiness ca. 9/10, but largest differences occur (0.4° - 0.5°C) when cloudiness is ca. 5/10 also (0.6° - 0.7°C) with wind velocity between 2 - 2.5m/s. The knowledge of artificial background and the rules which effect the state of atmosphere depending on the season of the year, time of day and meteorological conditions can be used in forecasting man-made climate changes. Producing appropriate formulas (simple equations, parabolic, sinusoid and hypersurface of regression) and using measured meteorological values outside urban area one can estimate temperature, humidity, wind velocity differences etc. between the urban area and its surroundings. Thus so it is possible to forecast e.g. air temperature for real estates expanding cities or planed towns, sites where no meteorological measurements were made.