@Article{CeballosBottSouz:2004:SiPhMo,
               author = "Ceballos, Juan Carlos and Bottino, Marcos Jorge and Souza, Jaidete 
                         Moneiro de",
          affiliation = "Inst Nacl Pesquisas Espaciais, Ctr Previsao Tempo \& Estudios 
                         Climat, Div Satelites \& Sistemas Ambientais, BR-12630000 Sao 
                         Paulo, Brazil",
                title = "A simplified physical model for assessing solar radiation over 
                         Brazil using GOES 8 visible imagery",
              journal = "Revista Brasileira de Geof{\'{\i}}sica",
                 year = "2004",
               volume = "109",
               number = "D 2",
                pages = "Art. No. D02211",
                month = "Jan.",
             keywords = "solar radiation, satellite, GOES 8, Brazil, atmospheric 
                         water-vapor, satelite data, synthetic atmospheres, infrared 
                         transmissiom, earths atmosphere, surface,absotion, budget, 
                         parameterization, calibration.",
             abstract = "Solar radiation assessment by satellite is constrained by physical 
                         limitations of imagery and by the accuracy of instantaneous local 
                         atmospheric parameters, suggesting that one should use simplified 
                         but physically consistent models for operational work. Such a 
                         model is presented for use with GOES 8 imagery applied to 
                         atmospheres with low aerosol optical depth. Fundamental 
                         satellite-derived parameters are reflectance and cloud cover. A 
                         classification method applied to a set of images shows that 
                         reflectance, usually defined as upper-threshold R-max in 
                         algorithms assessing cloud cover, would amount similar to0.465, 
                         corresponding to the transition between a cumuliform and a 
                         stratiform cloud field. Ozone absorption is limited to the 
                         stratosphere. The model considers two spectral broadband intervals 
                         for tropospheric radiative transfer: ultraviolet and visible 
                         intervals are essentially nonabsorbing and can be processed as a 
                         single interval, while near-infrared intervals have negligible 
                         atmospheric scattering and very low cloud transmittance. Typical 
                         values of CO2 and O-3 content and of precipitable water are 
                         considered. A comparison of daily values of modeled mean 
                         irradiance with data of three sites (in rural, urban industrial, 
                         and urban coastal environments), September-October 2002, exhibits 
                         a bias of +5 W m(-2) and a standard deviation of similar to15 W 
                         m(-2) (0.4 and 1.3 MJ m(-2) for daily irradiation). A comparison 
                         with monthly means from about 80 automatic weather stations 
                         (covering a large area throughout the Brazilian territory) still 
                         shows a bias generally within +/- 10 W m(-2) and a low standard 
                         deviation (<20 W m(-2)), but the bias has a trend in 
                         September-December 2002, suggesting an annual cycle of local R-max 
                         values. Systematic (mean) errors in partial cloud cover and in 
                         nearly clear-sky situations may be enhanced using regional values 
                         for atmospheric and surface parameters, such as precipitable 
                         water, R-max, and ground reflectance. The larger errors are 
                         observed in situations of high aerosol load (especially in regions 
                         with industrial activity or forest or agricultural fires). The 
                         last case is evident when sites in the Amazonian region or Sao 
                         Paulo city are selected. When considering daily values averaged 
                         within 2.5\&DEG; x 2.5\&DEG; cells, the standard error is lower 
                         than 20 W m(-2); present results suggest an annual cycle of mean 
                         bias ranging from +10 to -10 W m(-2), with an amplitude of -10 W 
                         m(-2). These values are close to the proposed requirements of 10 W 
                         m(-2) for the mean deviation and 25 W m(-2) for the standard 
                         deviation. It is expected that the introduction of a reference 
                         grid containing mean values of parameters within a cell could 
                         induce a decrease in the standard deviation of mean errors and the 
                         correction of their annual cycle. A model adaptation for assessing 
                         the effect of high aerosol loads is needed in order to extend 
                         improvements to the whole Brazilian area.",
           copyholder = "SID/SCD",
                 issn = "0102-261X",
             language = "en",
           targetfile = "Ceballos_A simplified.pdf",
        urlaccessdate = "12 maio 2024"
}