Estudo do campo térmico e das ilhas de calor urbano em Santa Maria - RS

Abstract

The objective of this work was to analyze the thermal field and the urban heat islands in Santa Maria and its surroundings, relating their thermal and spatial behaviors throughout both urban and natural interaction, facing the imposition of types of weather originated from Prefrontal Phase and Polar Domain atmospheric conditions, during the winter. The Thermal Dynamic Urban Weather System climatic perception channel, indicated by Monteiro (1976), was used as preliminary theoretical-methodological foundation. The study was developed in three phases. The first one was centered in elaborating the research goals. The second one was divided into two parts that consisted in the spatial analysis by elaborating thematic mapper, with the objective of making it possible to characterize geo-ecological and geo-urban variants inside the area in study, also in the analysis of the thermal field, in the MESO and TOPO weather scales, using image from the Landsat 7 ETM Satellite, on 06/19/2002. Field experiments inside the city were made in order to study the urban heat islands, in which 19 mini meteorological shelters were distributed with the objective of measuring the air temperature at 09h, 12h, 15h, 18h and 21h, on 08/04/2004 e 08/10/2004. Information on the air temperature was spatialized in isothermal cartograms over the Surfer6 program. Rhythmical analysis charts with daily meteorological data taken from the Santa Maria Meteorological Station, plus images from the GOES-E Satellite were elaborated to defined the types of weather traced in the days of the thermal image and from field observation. The third phase of this work consisted in the analysis of the results from the interpretation of the digital thermal cartography of surface, in which was possible to discern that the factors relief, vegetation, altimetry and use of rural soils control the mesoclimatic thermal responses. The greatest diversification in thermal responses detected concerned the topoclimate, due to the natural and urban factors, also to the Sun position during the imaging time, which have defined four distinct thermal situations: Warmer areas, with temperatures between 17° and 19°C; Moderate temperature areas, between 15° and 18°C; Mild temperature areas, between 13° and 17°C; and Lower temperature areas, between 10° and 16°C. Analysing the field experiments, it was possible to discern that on 08/04, due to the North Wind action in the dissipation of the thermal responses, there was no significant formation of Urban Heat Islands (UHI). Although, on the second day (08/10), under summarized Polar Domain conditions, the city registered UHI formation of high magnitude at every hour of observation, as well as the highest center-periphery thermal amplitude (10°C, at 12h). This way, it is possible to assert that the imposition of regional atmospheric systems acts directly in the definition of the thermal field and in the UHI formation, therefore being considered to effectuate a better urban planning and a greater understanding of the local climatic variants.