An Empirical Model to Estimate UV index in Some Upper Egypt Regions

Shazly, S. M. El; Kassem, Kh. O.; Hassan, A.A.; El-Nobi, Eman F.

doi:10.5923/j.re.20120205.05

Cited by 6 publications

(3 citation statements)

References 27 publications

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“…Surface albedo is determined mostly by snow amount and snow depth (Rieder et al, 2010) and plays a significant role at high-altitude and highlatitude sites, where UV irradiance can be strongly enhanced due to multiple occurrences of scattering and reflection between snow-covered ground and the atmosphere (Fitzka et al, 2012). Several studies have been conducted to quantify the effects of the abovementioned variables on the amount of UV irradiance reaching the ground, and many of them have done so by constructing empirical models with UV irradiance (or a related quantity) as a dependent variable (Díaz et al, 2000;Fioletov et al, 2001;de La Casinière et al, 2002;Foyo-Moreno et al, 2007;Antón et al, 2009;De Backer, 2009;Huang et al, 2011;Krishna Prasad et al, 2011;El Shazly et al, 2012).…”

Section: Introductionmentioning

confidence: 99%

Relations between erythemal UV dose, global solar radiation, total ozone column and aerosol optical depth at Uccle, Belgium

et al. 2014

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Abstract. At Uccle, Belgium, a long time series of simultaneous measurements of erythemal ultraviolet (UV) dose (S ery ), global solar radiation (S g ), total ozone column (Q O 3 ) and aerosol optical depth (τ aer ) (at 320.1 nm) is available, which allows for an extensive study of the changes in the variables over time. Linear trends were determined for the different monthly anomalies time series. S ery , S g and Q O 3 all increase by respectively 7, 4 and 3 % per decade. τ aer shows an insignificant negative trend of −8 % per decade. These trends agree with results found in the literature for sites with comparable latitudes. A change-point analysis, which determines whether there is a significant change in the mean of the time series, is applied to the monthly anomalies time series of the variables. Only for S ery and Q O 3 , was a significant change point present in the time series around February 1998 and March 1998, respectively. The change point in Q O 3 corresponds with results found in the literature, where the change in ozone levels around 1997 is attributed to the recovery of ozone. A multiple linear regression (MLR) analysis is applied to the data in order to study the influence of S g , Q O 3 and τ aer on S ery . Together these parameters are able to explain 94 % of the variation in S ery . Most of the variation (56 %) in S ery is explained by S g . The regression model performs well, with a slight tendency to underestimate the measured S ery values and with a mean absolute bias error (MABE) of 18 %. However, in winter, negative S ery are modeled. Applying the MLR to the individual seasons solves this issue. The seasonal models have an adjusted R 2 value higher than 0.8 and the correlation between modeled and measured S ery values is higher than 0.9 for each season. The summer model gives the best performance, with an absolute mean error of only 6 %. However, the seasonal regression models do not always represent reality, where an increase in S ery is accompanied with an increase in Q O 3 and a decrease in τ aer . In all seasonal models, S g is the factor that contributes the most to the variation in S ery , so there is no doubt about the necessity to include this factor in the regression models. The individual contribution of τ aer to S ery is very low, and for this reason it seems unnecessary to include τ aer in the MLR analysis. Including Q O 3 , however, is justified to increase the adjusted R 2 and to decrease the MABE of the model.

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Section: Introductionmentioning

confidence: 99%

Relations between erythemal UV dose, global solar radiation, total ozone column and aerosol optical depth at Uccle, Belgium

et al. 2014

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“…However, information from total ozone mapping spectrometer (TOMS) instruments was also used. El Shazly et al () reported using the applied version of the TOMS TOC processing algorithm and various TOMS techniques to monitor backward‐scattered Earth solar radiance in various bands. Moreover, Adam () showed that ozone measurements could be provided at Hurgada (27.23°N, 33.8°E) within the satellite spatial resolution (1° latitude × 1.25° longitude).…”

Section: Data Usedmentioning

confidence: 99%

Atmospheric modulations of the ratio of UVB to broadband solar radiation: effect of ozone, water vapour, and aerosols at Qena, Egypt

Adam

2013

Intl Journal of Climatology

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ABSTRACT:This study is an attempt to assess atmospheric modulations of the radiometric ratio of ultraviolet-B (UVB) to broadband solar radiation (G). It examines the role of the atmosphere as a filter, absorbing and scattering portions of the solar spectrum, shielding the biosphere from damaging doses of UVB. The diurnal variability of UVB/G at the Earth's surface has been evaluated by analysing 10-year hourly measurements of UVB and G on a horizontal surface at Qena, Egypt. The results show that, throughout the whole period, the values of hourly UVB/G varied from 0.03 to 0.73%, with an average value of 0.27%. This average represents only 17% of the corresponding value outside the atmosphere (1.56%). Moreover, the study quantifies the impact of ozone, water vapour, and aerosols on UVB/G under cloudless conditions. An analysis of the relationship between this ratio and the slant total ozone column (Z ) was also carried out. It showed that the ratio decreased with increasing Z . For Z = 537 DU, the average UVB/G was almost 53.47% lower than that at low Z (277 DU). The influence of precipitable water (W ) on UVB/G was determined under limited change in Z (<8.72%) and almost constant turbidity level (Ångström turbidity coefficient, β, of 0.19). The values of UVB/G increased with increasing W . For an average W = 1.13 cm, the average UVB/G was approximately 3.93% lower than at high W (2.82 cm). Moreover, the study illustrated the effect of aerosols on UVB/G when their influence on this ratio is greater than the impact of other atmospheric factors such as ozone and water vapour. It can be concluded that the ratio of the change in UVB/G to the change in β varies from 0.16 to 0.59%, with an average value of 0.33%.

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Section: Introductionmentioning

confidence: 99%

Relations between erythemal UV dose, global solar radiation, total ozone column and aerosol optical depth at Uccle, Belgium

Bock¹,

Backer²,

Malderen³

et al. 2014

Preprint

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Abstract. At Uccle, a long time series (1991–2013) of simultaneous measurements of erythemal ultraviolet (UV) dose, global solar radiation, total ozone column (TOC) and Aerosol Optical Depth (AOD) (at 320.1 nm) is available which allows for an extensive study of the changes in the variables over time. A change-point analysis, which determines whether there is a significant change in the mean of the time series, is applied to the monthly anomalies time series of the variables. Only for erythemal UV dose and TOC, a significant change point (without any known instrumental cause) was present in the time series around February 1998 and March 1998 respectively. The change point in TOC corresponds with results found in literature, where the change in ozone levels (around 1997) is attributed to the recovery of ozone. Linear trends were determined for the different (monthly anomalies) time series. Erythemal UV dose, global solar radiation and TOC all increase with respectively 7, 4 and 3% per decade. AOD shows an (insignificant) negative trend of −8% per decade. These trends agree with results found in literature for sites with comparable latitudes. A multiple linear regression (MLR) analysis is applied to the data in order to study the influence of global solar radiation, TOC and AOD on the erythemal UV dose. Together these parameters are able to explain 94% of the variation in erythemal UV dose. Most of the variation (56%) in erythemal UV dose is explained by global solar radiation. The regression model performs well with a slight tendency to underestimate the measured erythemal UV doses and with a Mean Absolute Bias Error (MABE) of 18%. However, in winter, negative erythemal UV dose values are modeled. Applying the MLR to the individual seasons solves this issue. The seasonal models have an adjusted R2 value higher than 0.8 and the correlation between modeled and measured erythemal UV dose values is higher than 0.9 for each season. The summer model gives the best performance, with an absolute mean error of only 6%. Again, global solar radiation is the factor that contributes the most to the variation in erythemal UV dose, so there is no doubt about the necessity to include this factor in the regression models. A large part of the influence of AOD is already represented by the global solar radiation parameter. Therefore the individual contribution of AOD to erythemal UV dose is so low. For this reason, it seems unnecessary to include AOD in the MLR analysis. Including TOC however, is justified as the adjusted R2 increases and the MABE of the model decreases compared to a model where only global solar radiation is used as explanatory variable.

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An Empirical Model to Estimate UV index in Some Upper Egypt Regions

Cited by 6 publications

References 27 publications

Relations between erythemal UV dose, global solar radiation, total ozone column and aerosol optical depth at Uccle, Belgium

Relations between erythemal UV dose, global solar radiation, total ozone column and aerosol optical depth at Uccle, Belgium

Atmospheric modulations of the ratio of UVB to broadband solar radiation: effect of ozone, water vapour, and aerosols at Qena, Egypt

Relations between erythemal UV dose, global solar radiation, total ozone column and aerosol optical depth at Uccle, Belgium

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