Angström-Prescott equation mean coefficients, solar radiation and reference crop evapotranspiration in Brasília
| Autor: | Karla Daniele e Silva Dornelas, Cícero Lopes da Silva, Carlos Alberto da Silva Oliveira |
|---|---|
| Přispěvatelé: | The objective of this work was to estimate Angström-Prescott equation mean coefficients in Brasília, DF, Brazil, and their effects on the calculations of global radiation (Rs) and reference crop evapotranspiration (ETo). It was used meteorological data from Embrapa Hortaliças weather station, from 1978 to 2003. The mean coefficients were determined by linear regression analysis considering monthly, annual and total periods. Using the calculated coefficients for different periods and those provided by FAO (0.25 and 0.50), Rs and ETo were estimated and their performances were evaluated. Monthly mean coefficient a varied from 0.241 to 0.345, and b from 0.430 to 0.515. Annual mean coefficients a and b were 0.278 and 0.498, and total means were 0.282 and 0.490, respectively. These coefficients did not differ from each other on radiation estimates. The month of July provided the worse estimates and performance. When using calculated Rs estimates with monthly, annual, total and FAO coefficients, estimated values of ETo did not differ from observed ones, providing excellent performance, despite the mean coefficient used. Depending on the final application, it is suggested the use of total mean coefficients due to their easiness to estimate the shortwave radiation. |
| Jazyk: | portugalština |
| Rok vydání: | 2006 |
| Předmět: |
Penman-Monteith-FAO
Energy balance duração de brilho solar Evapotranspiração Atmospheric sciences energy balance Weather station FAO-Penman-Monteith Crop evapotranspiration Linear regression actual duration of sunshine balanço de energia Animal Science and Zoology Radiação solar Shortwave radiation Agronomy and Crop Science Mathematics |
| Zdroj: | Pesquisa Agropecuária Brasileira, Volume: 41, Issue: 8, Pages: 1213-1219, Published: AUG 2006 Pesquisa Agropecuária Brasileira v.41 n.8 2006 Pesquisa Agropecuária Brasileira Empresa Brasileira de Pesquisa Agropecuária (Embrapa) instacron:EMBRAPA Repositório Institucional da UnB Universidade de Brasília (UnB) instacron:UNB |
| Popis: | O objetivo deste trabalho foi estimar os coeficientes médios a e b da equação de Angström-Prescott, em Brasília, e seus efeitos sobre o cálculo da radiação solar global (Rs) e da evapotranspiração de referência (ETo). Foram utilizados dados da estação meteorológica da Embrapa Hortaliças, do período de 1978 a 2003. Os coeficientes médios foram determinados por análise de regressão linear, no período todo e em períodos mensais e anuais. Utilizando-se o coeficiente calculado e os propostos pela FAO (0,25 e 0,50) estimaram-se Rs e ETo, e avaliaram-se os seus desempenhos. Os coeficientes médios mensais a variaram de 0,241 a 0,345, e b de 0,430 a 0,515. Os coeficientes médios anuais a e b foram 0,278 e 0,498, e os do período geral foram 0,282 e 0,490, respectivamente. A performance entre esses coeficientes na estimativa da radiação não diferiu. No mês de julho, foram verificados as piores estimativas e os piores desempenhos. Com as estimativas de Rs e os coeficientes médios calculados, as estimativas de ETo não diferiram dos observados, tendo-se constatado um ótimo desempenho, independentemente do coeficiente utilizado. Dependendo do tipo de aplicação final dos dados, recomenda-se utilizar, por sua simplicidade, os coeficientes médios obtidos para o período geral. The objective of this work was to estimate Angström-Prescott equation mean coefficients in Brasília, DF, Brazil, and their effects on the calculations of global radiation (Rs) and reference crop evapotranspiration (ETo). It was used meteorological data from Embrapa Hortaliças weather station, from 1978 to 2003. The mean coefficients were determined by linear regression analysis considering monthly, annual and total periods. Using the calculated coefficients for different periods and those provided by FAO (0.25 and 0.50), Rs and ETo were estimated and their performances were evaluated. Monthly mean coefficient a varied from 0.241 to 0.345, and b from 0.430 to 0.515. Annual mean coefficients a and b were 0.278 and 0.498, and total means were 0.282 and 0.490, respectively. These coefficients did not differ from each other on radiation estimates. The month of July provided the worse estimates and performance. When using calculated Rs estimates with monthly, annual, total and FAO coefficients, estimated values of ETo did not differ from observed ones, providing excellent performance, despite the mean coefficient used. Depending on the final application, it is suggested the use of total mean coefficients due to their easiness to estimate the shortwave radiation. |
| Databáze: | OpenAIRE |
| Externí odkaz: |
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