Effect of cloudiness on solar ultraviolet radiation reaching the surface

Ilyas, Mohammad

doi:10.1016/0004-6981(67)90098-4

Cited by 46 publications

(34 citation statements)

References 5 publications

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“…For this, the information routinely registered in most meteorological stations is used: cloud type and amount, expressed in terms of fractional cloud coverage in oktas, which are usually recorded in a 3-hourly database. This kind of approach has been followed in previous studies (Ilyas, 1987;Frederick and Snell, 1990;Frederick et al, 1993;Blumthaler et al, 1994Blumthaler et al, , 1996Thiel et al, 1997;Kuchinke and Núñez, 1999;Grant and Heisler, 2000;Josefsson and Landelius, 2000;Alados-Arboledas et al, 2003).…”

Section: Introductionmentioning

confidence: 99%

Influence of cloudiness over the values of erythemal radiation in Valencia, Spain

Esteve

Marı́n

Tena

et al. 2009

Intl Journal of Climatology

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The influence of cloudiness over experimental UV erythemal radiation (UVER) has been studied. This influence has been analysed considering total cloudiness and low clouds. The measurements of cloudiness correspond to the daily values registered at 13 : 00 GMT at the Meteorological Centre of Valencia, which is part of the State Agency of Meteorology of Spain (AEMET). The UVER measurements were made using a YES UVB-1 radiometer located on the roof terrace of the Physics Faculty at the Burjassot Campus, Valencia (latitude 39.508°, longitude −0.418°, 60 m above sea level). First, a statistical analysis of cloudiness at 13 : 00 GMT in Valencia was carried out, confirming that the situation is mainly clear skies or very few clouds. Next, the influence of cloudiness on experimental UVER values was analysed, for both total cloudiness and low clouds. The experimental UVER values decrease as cloudiness increases for all solar zenith angles (SZA), and this reduction increases with the zenith angle. Next, the cloud modification factor (CMF) has been defined to reduce the influence of the zenith angle and ozone over the UVER. In order to quantify the relationship between CMF and the degree of cloudiness in oktas, linear, quadratic and potential regressions for both total cloudiness and low clouds have been calculated. Transmissivity due to total cloudiness and for overcast skies reaches 40%. On the other hand, the analysis of the influence over the zenith angle shows that CMF reduces as the zenith angle increases in the case of both total cloudiness and low clouds. With regard to the low cloud CMF, the results are comparable to those proposed by the COST-713 Action "UV-B Forecasting" for partially cloudy or cloudy skies (70% and 50%, respectively). Finally, the relationship between the CMF and the clearness index (k T ) has been analysed, as both parameters are simple indicators of cloudiness. It has been proved that such relationship is close to unity for zenith angles in the mid-range, while the CMF is greater than k T for lower SZA and is less than k T for high SZA, which indicates a certain dependence of these two parameters on the zenith angle.

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Section: Introductionmentioning

confidence: 99%

Influence of cloudiness over the values of erythemal radiation in Valencia, Spain

Esteve

Marı́n

Tena

et al. 2009

Intl Journal of Climatology

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“…According to four years of observation by Ilyas (1987), the UV radiation under a cloud cover of 83% declines to 50% of that on a sunny day. The UVB radiation under 100% cloud cover declines to 45% of that on a sunny day.…”

Section: Discussionmentioning

confidence: 99%

“…The factors affecting UVI variations are complex, and their spatial and temporal changes are diverse at the decadal scale; therefore, there is a certain degree of difficulty in fully describing the characteristics and causes of UV variations when using both methods of field measurements and model simulation (Ilyas, 1987;Bais et al, 1993). The long-term changes of UVI were not driven entirely by a single factor, such as total ozone, but rather by a combination of total cloud amount, aerosols, albedo, and other factors, as well as geographical location and elevation.…”

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confidence: 99%

Spatial Statistical Analyses of Global Trends of Ultraviolet B Fluxes in the Continental United States

Gao

Chang

2012

GIScience & Remote Sensing

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Abstract. Many environmental factors, such as stratospheric ozone, aerosols, and clouds, may affect ultraviolet (UV) irradiance. The aim of this study is to investigate the possible association between ultraviolet B (UVB) radiation and total cloud amount, ozone, and aerosols simultaneously, leading to the assessment of possible impacts of climate change on UVB flux variations in the continental United States (U.S.). Spatiotemporal correlation analyses were conducted, based on data collected from the Total Ozone Mapping Spectrometer (TOMS) and the International Satellite Cloud Climatology Project (ISCCP), with a geographic information system (GIS). Findings indicate that in the past 22 years, while ozone decreased and aerosols increased across the U.S., the UVB decrease in the northern states was consistent with an increase in aerosols and total cloud amount. Therefore, to some extent, the trend characteristics of UVB over the U.S. between 1980 and 2002 were simultaneously affected by such dominant factors as total ozone and by such auxiliary factors as aerosol and total cloud amount. Climate change impact resulting in higher total cloud amount in the northern states might result in lower UVB in the future.

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“…There are various studies addressing the estimation of cloud effects on solar UV irradiance as a function of either the observed cloud amount (Ilyas, 1987;Lubin and Frederick, 1991;Bais et al, 1993;Blumthaler et al, 1996;Nemeth et al, 1996;Schafer et al, 1996;Thiel et al, 1997;Kuchinke and Nunez, 1999;AladosArboledas et al, 2003;Alados et al, 2004), the cloud effect on other spectral ranges of solar irradiance (Alados et al, 2000;Foyo-Moreno et al, 2001 or a combination of the two (Schwander et al, 2002). A different approach has been followed by Sabburg and Wong (2000) that used additional information on the cloud field obtained by sky cameras.…”

Section: Ann Designmentioning

confidence: 99%

“…In previous works (AladosArboledas et al, 2003;Alados et al, 2004), we have characterised the cloud effects on UVER using information routinely registered in most meteorological stations: cloud type and amount, expressed in terms of fractional cloud coverage in octas (eighths). This kind of approach has been followed in different studies (Ilyas, 1987;Frederick and Snell, 1990;Frederick et al, 1993;Blumthaler et al, 1994Blumthaler et al, , 1996Thiel et al, 1997;Kuchinke and Nunez, 1999;Grant and Heisler, 2000;Josefsson and Landelius, 2000). The approach followed in these studies included modelling cloud effects using non-linear functions in combination with more or less complex models for cloudless skies.…”

Section: Introductionmentioning

confidence: 99%

Neural network for the estimation of UV erythemal irradiance using solar broadband irradiance

Alados

Gomera

Foyo-Moreno

et al. 2007

Intl Journal of Climatology

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Abstract:In recent years there has been a substantial increase in attempts to model radiative flux of ultraviolet radiation, UV. In this paper we present the development of an artificial neural network (ANN) model that can be used to estimate solar UV erythemal irradiance, UVER, based on optical air mass, ozone columnar content and broadband solar irradiance. The study was developed at seven stations in the Iberian Peninsula using data recorded at A Coruña, Málaga, Murcia and Santander, during 2000-2003; at Madrid in the period at Valencia in 2000 at Valencia in , 2001 at Valencia in and 2003 and at Zaragoza, from 2001 to 2003. The UVER observations are recorded as half-hour average values. The measurements were performed in the framework of the Spanish UV-B radiometric network operated and maintained by the Spanish Meteorological Institute. In order to train and validate the Multi-layer Perceptron neural networks, independent subsets of data were extracted from the complete database at each station. The networks developed at each place when applied to an independent data set recorded at the same location provide estimates with mean bias deviation less than 1% and root mean square deviation below 17% for all the sites. The generalization network developed using data registered at A Coruña, Madrid, Murcia and Zaragoza provides estimates at all the locations with RMSD below 19%. According to these results, the use of solar broadband irradiances for the estimation of ultraviolet erythemal irradiance provides a tool that can solve the difficulties associated to the retrieval of appropriate information on the cloud field by human observers. In this sense, the proposed method seems appropriate to use the widespread networks of solar broadband irradiance to obtain ultraviolet erythemal irradiance data sets in places where this radiative flux is not measured or to extend back in time the existing data sets.

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Effect of cloudiness on solar ultraviolet radiation reaching the surface

Cited by 46 publications

References 5 publications

Influence of cloudiness over the values of erythemal radiation in Valencia, Spain

Influence of cloudiness over the values of erythemal radiation in Valencia, Spain

Spatial Statistical Analyses of Global Trends of Ultraviolet B Fluxes in the Continental United States

Neural network for the estimation of UV erythemal irradiance using solar broadband irradiance

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