Mudanças climáticas urbanas.

Abstract

The research had a basic assumption, namely the fact that the growth of the cities has been taking to great modifications of its structures, provoking its pronounced heating, mainly due to asphalt's application and construction of buildings with mirrored windows. Trying to study that situation in the state of Paraiba, experiments with urban microclimate were driven in the winter periods (July-August) and summer (December) of 1997 in the cities of Campina Grande and Patos, objectifying to study the microclimate and the influence of the asphalt surfaces, pavement and square, in the urban heating. So that, micrometeorological stations were installed in the mentioned surfaces, equipped with system of data's acquisition (micrologger 21X), that facilitated instantaneous readings of global solar radiation, reflected radiation, radiation balance, flow of heat, temperature and humidity of the air, temperature of the surface and speed of the wind. Observations were also made with mobile transecto. Besides the comparison among the parameters observed on the three studied areas, the temperature of the air was also compared with that observed in the meteorological station. The results showed that the asphalt surface is the hottest of the three studied urban areas. In the city of Campina Grande, the temperature of the asphalt reached hourly averages between 14 and 15 hours of 60,8°C and 47,5°C, respectively, in the summer and winter, while in the city of Patos it arrived at 63,9°C and 55,5°C in the two mentioned periods. A fact that gets attention is that, although the asphalt is the warmest surface, the temperature of the air on the pavement street was larger than on the asphalt in the city of Patos, in the winter and in the summer and, in Campina Grande, in the summer. That fact can be associated to the great reflection of solar radiation by the pavement surface that, although it contributes to liven up the temperature of the surface, provides more radiation of short waves to be absorbed by the vapor of water in the adjacent atmosphere. Observations with mobile transectos made in Patos, indicate that the forest can contribute to reduce the temperature of the air in up to 1,8°C in asphalt paved street and in 1,3°C in pavement street Last, the close made observations to walls of several colors, they showed that on the sunny side of the street, the temperature went 4,7°C superior on the average to that observed on the shaded side and that the more dark it goes the color of to wall, larger heating this will have.