Determination of Ångström's turbidity coefficient from direct total solar irradiance measurements

Louche, A.; Maurel, Michel; Simonnot, G.; Peri, Giorgia; Iqbal, M.

doi:10.1016/0038-092x(87)90031-4

Cited by 98 publications

(42 citation statements)

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“…Comparison of estimated turbidity values against turbidity values derived from aerosol optical thickness data has shown that the performance of the algorithm by Louche et al (1987) is significantly improved by setting α to the more frequent hourly value obtained for the location. In such conditions, Louche's and Gueymard's methods present a similar RMSE of around 34%.…”

Section: Discussionmentioning

confidence: 99%

“…All three models considered herein (Dogniaux, 1974;Louche et al, 1987;Gueymard and Vignola, 1998) are well established. They have been adequately described in sufficient detail in the previously cited references.…”

Section: Description Of the Algorithms To Calculate Coefficient βmentioning

confidence: 99%

“…The method proposed by Louche et al (1987) was derived from the model C by Iqbal (1983), but using the expression by Mächler (1983) for the transmittance due to aerosol attenuation. TheÅngström turbidity coefficient obtained by Louche et al (1987), β L , is expressed as:…”

Section: Louche's Algorithmmentioning

confidence: 99%

“…However, these spectral measurements have only recently been established and the sparseness of this data both spatially and temporally makes it impossible to study current long-term turbidity trends. To circumvent this limitation, several methods based on broad-band measurements of solar radiation and related atmospheric parameters can be used in the first place (Louche et al, 1987;Pinazo et al, 1995;Gueymard and Vignola, 1998;Power, 2001). These methods estimate the turbidity coefficient β and assume a constant value for the wavelength exponent α, which is often set to 1.3, following the reference value originally proposed byÅngström for continental aerosols.…”

Section: Introductionmentioning

confidence: 99%

“…They were formulated by Dogniaux (1974), Louche et al (1987) and Gueymard and Vignola (1998), respectively. The first two were selected because of their simplicity and extensive use in order to either estimate solar radiation components from parametric models or to study seasonal turbidity variations (Sinha et al, 1998;Pedrós et al, 1999;Batlles et al, 2000;Li and Lam, 2002;Janjai et al, 2003), whereas the third one is new.…”

Section: Introductionmentioning

confidence: 99%

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Estimate of the atmospheric turbidity from three broad-band solar radiation algorithms. A comparative study

López

Batlles²

2004

Ann. Geophys.

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Abstract. Atmospheric turbidity is an important parameter for assessing the air pollution in local areas, as well as being the main parameter controlling the attenuation of solar radiation reaching the Earth's surface under cloudless sky conditions. Among the different turbidity indices, theÅngström turbidity coefficient β is frequently used. In this work, we analyse the performance of three methods based on broadband solar irradiance measurements in the estimation of β. The evaluation of the performance of the models was undertaken by graphical and statistical (root mean square errors and mean bias errors) means. The data sets used in this study comprise measurements of broad-band solar irradiance obtained at eight radiometric stations and aerosol optical thickness measurements obtained at one co-located radiometric station. Since all three methods require estimates of precipitable water content, three common methods for calculating atmospheric precipitable water content from surface air temperature and relative humidity are evaluated. Results show that these methods exhibit significant differences for low values of precipitable water. The effect of these differences in precipitable water estimates on turbidity algorithms is discussed. Differences in hourly turbidity estimates are later examined. The effects of random errors in pyranometer measurements and cloud interferences on the performance of the models are also presented. Examination of the annual cycle of monthly mean values of β for each location has shown that all three turbidity algorithms are suitable for analysing long-term trends and seasonal patterns.

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Section: Discussionmentioning

confidence: 99%

Section: Description Of the Algorithms To Calculate Coefficient βmentioning

confidence: 99%