The basic characteristics of the Belgrade’s heat island

Abstract

The urban heat island, as a phenomenon due to the higher air temperature in the cities as compared to their immediate surroundings, represents the most important consequence of the urbanization influence on the topoclimate. As compared to the smaller cities in its surroundings, Belgrade's average annual temperature is from 0,4 to 1,0 ?C higher (period 1961-1990). A very liable index of the Belgrade's heat island is the air temperature measured at the airport in Surcin. In the period from 1971-1990. average annual air temperature at the airport was 11,2 ?C, and in the city center it was 0,7 ?C higher. Belgrade has a higher absolute minimal temperature than its surroundings during every month. In the last climatic period the absolute temperature minimum in Belgrade was even 5,4 ?C higher than the highest value measured within this parameter in its wider surroundings (Veliko Gradiste -26,4 ?C). In the above mentioned twenty years period the absolute air temperature minimum in Surcin was -26,0 ?C, and in the city center only -18,2 ?C. The number of the frosty days at the airport was 77,8, and in Belgrade 58,2. Although the heat island of Belgrade was formed together with formation of the city, it was more evident at the beginning of the 20th century (0,4 ?C). During the next five to six decades a faster intensity growth was recorded (up to 0,9 ?C). This coincides with the period of the population growth as well as with development of the city activities, industry above all. During one year the intensity of the Belgrade's heat island reached its maximum in winter. In January the city, as compared to Surcin, was warmer for about 1,0 ?C, and in September for only 0,1 ?C. The daily variations of the heat island are such that it reaches its highest intensity during the evening hours (at 9 p.m. 0,9 ?C). If the average values of the extreme daily temperatures are being examined, one can see a distinct difference: average city minimums are 1,5 ?C higher than the airport minimums, while the maximums are only 0,2 ?C higher. During winter, in concrete anticyclonic conditions, it can be 10 ?C warmer in the city than in the immediate surroundings. Together with the perennial growth of heat island intensity, its "space range" also expands. The space structure of the heat island is very distinct. Exceptions in the temperature values between certain points of measurements in the winter morning hours can go up to 6-8 ?C.