Os efeitos de áreas agrícolas urbanas na intensidade das ilhas de calor em Florianópolis - SC
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Data
2020-04-02
Autores
Silva, Gustavo Henrique Pereira da [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
O acelerado crescimento das cidades associado a um planejamento ineficiente ocasionou inúmeros problemas ambientais que recaem sobre a qualidade de vida da população. Nesse contexto de alterações das condições do ambiente natural, inúmeros estudos científicos foram suscitados, dentre eles, destacam-se os que se propuseram a estudar o clima das cidades. Diante disso, esta pesquisa baseou-se na proposta teórica e metodológica do Sistema Clima Urbano (S.C.U), com enfoque no subsistema termodinâmico e teve como objetivo central investigar os efeitos de áreas agrícolas urbanas na intensidade das ilhas de calor em Florianópolis - SC, no que se refere às condições de temperatura, um dos principais elementos climáticos responsáveis pelo conforto térmico. A ênfase dada à Florianópolis relaciona-se à presença de um marco legal que prevê a implantação e apoio à prática agrícola nos espaços intraurbano e periurbano. Os procedimentos metodológicos realizados, consistiram na busca por dados de temperatura a partir de técnicas de sensoriamento remoto e pontos fixos. Foram tratadas e analisadas as imagens do satélite Landsat-8, que mostraram diferenças nas características térmicas dos alvos, comparando-se áreas densamente construídas com áreas não construídas, apresentando intensidades de ilhas de calor de superfície de até 14ºC. As áreas com maior desenvolvimento vegetativo, com destaque para aquelas localizadas nos topos dos morros, apresentaram as menores temperaturas das cenas e as áreas de agricultura urbana e periurbana se apresentaram até 8ºC menos aquecidas do que as áreas densamente ocupadas. Este resultado revelou uma relação inversamente proporcional entre os valores de temperaturas superficiais e de NDVI (Índice de Vegetação por Diferença Normalizada). Os 12 pontos fixos monitorados, distribuídos na malha urbana, possibilitaram a coleta da temperatura do ar no mês de fevereiro e março de 2019. Os pontos monitorados apresentaram variações térmicas nas diferentes horas do dia, associadas aos usos e ocupação da terra no entorno, à atuação dos diferentes sistemas atmosféricos, à incidência da radiação solar etc. A forma alongada da ilha de Santa Catarina na orientação Norte-Sul, propiciou em seus 54 km de extensão particularidades à atmosfera local, que foram observadas principalmente no período diurno (6h, 9h, 12h, 15h), em que os pontos localizados ao Sul da ilha (pontos 1, 2, 3 e 4), incluso os de agricultura urbana (pontos 1 e 2), com cobertura vegetal, se apresentaram mais aquecidos que os demais. No período noturno, principalmente sob condições atmosféricas estáveis, observou-se que os pontos urbanos, com destaque para aqueles localizados em áreas mais densamente ocupadas, registraram as maiores intensidades térmicas, com até 4ºC. Durante a noite, em muitos dias de análise, as áreas de agricultura urbana converteram-se em ilhas de frescor, o que releva a importância deste tipo de uso da terra na redução das temperaturas em ambiente urbano.
The accelerated growth of cities associated with inefficient planning has caused numerous environmental issues that affect the population quality of life. In this context of changes in natural environment conditions, several scientific studies have been carried out, among which stand out those who focused on studying the climate of cities. Therefore, the present research was based on the theoretical and methodological proposal of the Urban Climate System (UCS), with emphasis on the thermodynamic subsystem. The main objective was to investigate the effects of urban agricultural areas on the intensity of heat islands in Florianópolis - SC, with regard to temperature conditions, one of the main climatic elements responsible for thermal comfort. The emphasis given to Florianópolis is related to the presence of a legal framework that provides for the implementation and support of agricultural practice in intra-urban and peri-urban spaces. The methodological procedures performed consisted of researching temperature data using remote sensing techniques and fixed points. Landsat-8 satellite images were treated and analyzed, which presented differences in the thermal characteristics of the targets, comparing densely built areas with non-built spaces, revealing intensities of surface heat islands of up to 14ºC. The areas with the highest vegetative development, with emphasis on those located at the top of hills, presented the lowest temperatures in the scenes, and the areas of urban and peri-urban agriculture were up to 8ºC less heated than densely occupied areas. Such result revealed an inversely proportional relationship between the values of surface temperatures and Normalized Difference Vegetation Index (NDVI). The 12 monitored fixed points, distributed in the urban grid, enabled the collection of air temperature in February and March 2019. The monitored sites showed thermal variations at different times of the day, which is associated with the uses and occupation of the surrounding land, the performance of different atmospheric systems, the incidence of solar radiation, etc. The elongated shape of the Santa Catarina island in North-South axis, provided in its 54 km of extension particularities to the local atmosphere, which were observed mainly during daytime (6 am, 9 am, 12 pm, 3 pm), in which the points located to the South from the island (points 1, 2, 3 and 4), including those of urban agriculture (points 1 and 2) with vegetation cover, were hotter than the others. At night, mainly under stable atmospheric conditions, it was observed that urban points, with emphasis on those located in more densely occupied areas, registered the highest thermal intensities, with up to 4ºC. During nighttime, in many days of analysis, the areas of urban agriculture became islands of freshness, which highlights the importance of this type of land use in reducing temperatures in an urban environment.
The accelerated growth of cities associated with inefficient planning has caused numerous environmental issues that affect the population quality of life. In this context of changes in natural environment conditions, several scientific studies have been carried out, among which stand out those who focused on studying the climate of cities. Therefore, the present research was based on the theoretical and methodological proposal of the Urban Climate System (UCS), with emphasis on the thermodynamic subsystem. The main objective was to investigate the effects of urban agricultural areas on the intensity of heat islands in Florianópolis - SC, with regard to temperature conditions, one of the main climatic elements responsible for thermal comfort. The emphasis given to Florianópolis is related to the presence of a legal framework that provides for the implementation and support of agricultural practice in intra-urban and peri-urban spaces. The methodological procedures performed consisted of researching temperature data using remote sensing techniques and fixed points. Landsat-8 satellite images were treated and analyzed, which presented differences in the thermal characteristics of the targets, comparing densely built areas with non-built spaces, revealing intensities of surface heat islands of up to 14ºC. The areas with the highest vegetative development, with emphasis on those located at the top of hills, presented the lowest temperatures in the scenes, and the areas of urban and peri-urban agriculture were up to 8ºC less heated than densely occupied areas. Such result revealed an inversely proportional relationship between the values of surface temperatures and Normalized Difference Vegetation Index (NDVI). The 12 monitored fixed points, distributed in the urban grid, enabled the collection of air temperature in February and March 2019. The monitored sites showed thermal variations at different times of the day, which is associated with the uses and occupation of the surrounding land, the performance of different atmospheric systems, the incidence of solar radiation, etc. The elongated shape of the Santa Catarina island in North-South axis, provided in its 54 km of extension particularities to the local atmosphere, which were observed mainly during daytime (6 am, 9 am, 12 pm, 3 pm), in which the points located to the South from the island (points 1, 2, 3 and 4), including those of urban agriculture (points 1 and 2) with vegetation cover, were hotter than the others. At night, mainly under stable atmospheric conditions, it was observed that urban points, with emphasis on those located in more densely occupied areas, registered the highest thermal intensities, with up to 4ºC. During nighttime, in many days of analysis, the areas of urban agriculture became islands of freshness, which highlights the importance of this type of land use in reducing temperatures in an urban environment.
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Palavras-chave
Agricultura urbana e periurbana, Ilhas de calor urbana, Clima urbano, Florianópolis - SC, Urban and peri-urban agriculture, Urban heat islands, Urban climate