ABSTRACT
The objective of this study was to perform a temporal and spatial analysis of the changes in the past global solar radiation based on climate models and remote sensing data in the State of Rio de Janeiro, Brazil for the baseline period (1961-1990). Data from two climate models - the Canadian Centre for Climate Modelling and Analysis and Geophysical Fluid Dynamic Laboratory, were used for the A1B intermediate scenario, data from Conventional Weather Stations and orbital sensor Moderate Resolution Imaging Spectroradiometer (MODIS) MODIS Land Cover Type (MCD12Q1). The results of the Spatial Dependence Degree indicate that the best model to represent the global solar radiation is CCCMA-Exponential dry 70.01 and rainy 0.21 respectively. It was possible to verify that in places where the areas are occupied by forests there was reduction of global solar radiation for both dry and rainy periods of approximately 13 MJ m-2d-1. These results indicate that these forest areas can function as islands of freshness, while maintaining the thermal comfort balanced. It was concluded that the dry period had the highest values of solar radiation compared to the rainy (57%), which can be justified by the occurrence of fires in Rio de Janeiro.
O objetivo deste estudo foi realizar uma análise temporal e espacial das mudanças ocorridas da radiação solar global passada baseado em modelo climáticos e sensoriamento remoto no Estado do Rio de Janeiro, Brasil para o período baseline (1961-1990). Utilizaram-se dados de dois modelos climáticos o Canadian Centre for Climate Modelling and Analysis) e Geophysical Fluid Dynamic Laboratory para o cenário intermediário A1B, dados de Estações Meteorológicas Convencionais e do sensor orbital Moderate Resolution Imaging Spectroradiometer (MODIS) MODIS Land Cover Type (MCD12Q1). Os resultados do Grau de Dependência Espacial indicam que o melhor modelo que representa a radiação solar global é o CCCMA-Exponencial seco 70.01 e chuvoso de 0.21 respectivamente. Foi possível verificar que em locais onde as áreas são ocupadas por florestas houve redução da radiação solar global para os dois períodos seco e chuvoso de aproximadamente 13 MJ.m-2.dia-1. Estes resultados indicam que estas áreas de florestas podem funcionar como ilhas de frescor, mantendo o conforto térmico equilibrado. Conclui-se que o período seco apresentou maiores valores de radiação solar em comparação ao chuvoso (57%), que pode ser justificado pela ocorrência de queimadas no Rio de Janeiro.
Subject(s)
Forests , Solar Radiation , Remote Sensing Technology , Spatio-Temporal Analysis , Satellite ImageryABSTRACT
RESUMO A qualidade térmica do ambiente urbano é um dos problemas enfrentados pelas cidades atualmente. A forma de ocupação urbana altera o balanço de energia nas cidades, provocando frequentemente um aquecimento do ar nas camadas intraurbanas e criando microclimas variados. No entanto, mapear os microclimas urbanos possibilitando apoio à tomada de decisões de planejamento urbano é uma tarefa complexa e de longo prazo. Procurando demonstrar as potencialidades térmicas oferecidas por alguns índices urbanísticos usualmente aplicados por órgãos decisores, este artigo buscou verificar a influência dos coeficientes de ocupação, de aproveitamento e de cobertura vegetal sobre a temperatura do ar em microclimas urbanos. Em uma fração urbana de ocupação consolidada, foram realizadas medições em campo, que serviram de base para a validação de um modelo computacional de simulação do ambiente térmico urbano. Posteriormente foram feitas simulações com diferentes índices urbanísticos e desenvolvidos mapas térmicos. Os resultados apontaram que os coeficientes estudados devem ser mais explorados termicamente, principalmente se considerado o coeficiente de cobertura vegetal, cuja alteração de valores pode levar a diferenças mais significativas na temperatura do ar.
ABSTRACT The thermal quality of the urban environment is nowadays one of the problems faced by cities. The form of urban occupation changes the energy balance within cities, often causing a warming of the air in the urban canopy layer and generating a variety of microclimates. Mapping the urban microclimates to enable the support of decisions in urban planning is a complex and long-term task. Aiming to demonstrate the thermal potentiality offered by some urban indexes usually applied by decision-makers, this paper seeks to investigate the influence of the coefficient of occupation, the floor space index and the vegetation cover index on the air temperature of urban microclimates. At an urban zone already consolidated, field measurements were performed, allowing the creation of a basis for the validation of a computational model applied for simulating the urban thermal environment. Finally, different indexes were simulated, and thermal maps were developed. The results showed that the thermal potential of the studied coefficients should be further explored, especially considering the coefficient of vegetation, whose range of values can lead to more significant differences in the air temperature.
ABSTRACT
Aims: The study of urban heat islands and traditionally relies on simplistic descriptors such as “urban” and “rural”. While these descriptors may be evocative of the landscape, they are insufficient in providing information like its site properties which have direct impacts on the surfacelayer climate. The newly developed “Local Climate Zones” (LCZ) characterization scheme from Oke and Stewart [1] was applied to three case study areas to provide a more objective assessment of the urban heat island (UHI) phenomenon in Singapore. Study Design: The three step procedure of site metadata collection, definition of the thermal source area, and selection of the appropriate climate zone was followed for the three case study areas representing green space, a typical high rise residential housing area, and the CBD to identify and explain UHI characteristics. Place and Duration of Study: Singapore; January-March, 2014. Methodology: Characterization of the three study sites included scoring of a sky view factor, canyon aspect ratio, terrain roughness, building surface fraction, impervious surface fraction, surface energy admittance, surface albedo, and anthropogenic heat flux based on observation, photography, and Google Earth imagery, to determine the LCZ class. Temperature, wind speed, and relative humidity were recorded on an hourly basis at each site using Kestrel 4000 weather trackers and data logger at a 2 m elevation for five consecutive days in January, 2014. Results: The three study sites were characterized as LCZ 1 (compact high rise (CBD)), LCZ 4 (open high rise (high rise residential housing area)), and LCZ 9 (sparsely built (green space)). The temperature for LCZ 9 was lower than the other two sites, with the greatest UHI intensity (difference between mean air temperature being 2.01ºC between LCZ 4 and LCZ 9. Interestingly, although the CBD area was warmer than the open high rise area between midnight and 6 a.m., a typical UHI phenomenon, the mean air temperature for the entire 5 day period was greater at the open rise site. Conclusion: The lower temperature at the green space site emphasizes the importance of such spaces in the urban landscape as a means to make cities more liveable and resilient to climate change impacts. The higher mean temperature at the open high rise site as compared to the CBD site was related to anthropogenic activities (particularly traffic patterns), landscaping/green space, and the influence of a large green-certified building within the circle of influence at the CBD site. Overall, the use of LCZ in quantifying the UHI magnitude of Singapore was relatively straightforward to apply and this approach should be widely applied to more objectively investigate the UHI phenomenon, particularly in tropical cities.