Global and diffuse solar irradiances in urban and rural areas in southeast Brazil

• Published in: Theoretical and applied climatology Vol. 93; no. 1-2; pp. 57 - 73
• Main Authors: Codato, G., Oliveira, A. P., Soares, J., Escobedo, J. F., Gomes, E. N., Pai, A. D.
• Format: Journal Article
• Language: English
• Published: Vienna Springer-Verlag 01.06.2008; Springer; Springer Nature B.V
• Subjects: Aquatic Pollution; Atmospheric Protection/Air Quality Control/Air Pollution; Atmospheric Sciences; Climatology; Earth and Environmental Science; Earth Sciences; Earth, ocean, space; Exact sciences and technology; External geophysics; Meteorology; Particulate matter; Radiative transfer. Solar radiation; Rural areas; Seasonal variations; Solar radiation; Spatial distribution; Sugar; Sugarcane; Waste Water Technology; Water Management; Water Pollution Control; South America; Brazil; Brazil, Sao Paulo, Botucatu; ASW, Brazil, Sao Paulo; ASW, Brazil; Sugar Cane; Atmos Environ; Global Solar Radiation; Solar Irradiance; Gross National Product; Global radiation; Diffuse solar radiation; aerosols; Regional scope; Environmental factor; Wind effect; urban areas; Clear sky; Sea breeze; irradiance; spatial variations; rural areas; seasonal variations; Anthropogenic factor
• ISSN: 0177-798X; 1434-4483
• DOI: 10.1007/s00704-007-0326-0

Summary The seasonal evolution of daily and hourly values of global and diffuse solar radiation at the surface are compared for the cities of São Paulo and Botucatu, both located in Southeast Brazil and representative of urban and rural areas, respectively. The comparisons are based on measurements of global and diffuse solar irradiance carried out at the surface during a six year simultaneous period in these two cities. Despite the similar latitude and altitude, the seasonal evolution of daily values indicate that São Paulo receives, during clear sky days, 7.8% less global irradiance in August and 5.1% less in June than Botucatu. On the other hand, São Paulo receives, during clear sky days, 3.6% more diffuse irradiance in August and 15.6% more in June than Botucatu. The seasonal variation of the diurnal cycle confirms these differences and indicates that they are more pronounced during the afternoon. The regional differences are related to the distance from the Atlantic Ocean, systematic penetration of the sea breeze and daytime evolution of the particulate matter in São Paulo. An important mechanism controlling the spatial distribution of solar radiation, on a regional scale, is the sea breeze penetration in São Paulo, bringing moisture and maritime aerosol that in turn further increases the solar radiation scattering due to pollution and further reduces the intensity of the direct component of solar radiation at the surface. Surprisingly, under clear sky conditions the atmospheric attenuation of solar radiation in Botucatu during winter – the biomass burning period due to the sugar cane harvest – is equivalent to that at São Paulo City, indicating that the contamination during sugar cane harvest in Southeast Brazil has a large impact in the solar radiation field at the surface.