Diffuse UV erythemal radiation experimental values
TL;DR: In this paper, the average values of the diffuse UVER fraction in relation to the clearness index kt were analyzed in order to study the average value of the UV fraction.
Abstract: [1] Measurements of diffuse UV erythemal radiation (UVER) using a shadowband have been corrected using the models proposed by Drummond (1956), LeBaron et al. (1990), and Batlles et al. (1995). Two different methods were used to validate these models: intercomparison with an Optronic OL754 spectroradiometer and comparison with the values simulated by two radiative transfer codes, SMARTS and SBDART. For this comparison only clear days have been used. The corrected experimental values were analyzed in order to study the average values of the diffuse UVER fraction in relation to the clearness index kt. These varied between 62%, for kt close to 0.8, and 93% for kt of 0.2–0.3. Finally, a study of the monthly average and extreme values of the UV Index for diffuse radiation is presented, showing a maximum value of 6 in June.
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TL;DR: The SMARTS spectral radiation model has been extensively used in the last 25 years as mentioned in this paper, and its main modeling algorithms, regarding both absorption and scattering from various atmospheric constituents are described, highlighting the new developments in the model's latest version (2.9.8).
69 citations
TL;DR: In this paper, a study of a strong desert dust episode over the Iberian Peninsula, and its effect on the spectral ultraviolet (UV) irradiance in Granada, Spain, is presented.
Abstract: This paper presents a study of a strong desert dust episode over the Iberian Peninsula, and its effect on the spectral ultraviolet (UV) irradiance in Granada, Spain. Remote sensing measurements, forecast models, and synoptic analysis are used to identify a Saharan desert dust outbreak that affected the Iberian Peninsula starting 20 July 2009. Additionally, a Bentham DMc150 spectroradiometer is employed to obtain global, direct and diffuse spectral UV irradiances every 15 minutes in Granada. The desert dust caused a large attenuation of the direct UV irradiance (up to 55%), while the diffuse UV irradiance increased up to 40% at 400 nm. The UVSPEC/LibRadtran radiative transfer model is used to study the spectral dependence of the experimental UV irradiance ratios (ratios of spectral irradiance for the day with the highest aerosol load to that measured in days with lowmoderate load). The spectral increase or decrease of the UV direct irradiance ratios depends on a new parameter: a threshold wavelength. The spectral dependence of the UV diffuse irradiance ratio can be explained because under the influence of the intense dust outbreak, the Mie scattering by aerosols at shorter wavelengths is stronger than the Rayleigh scattering by gases. Finally, the sensitivity analysis of the aerosol absorption properties shows a substantial attenuation of UV spectral irradiance with a weak spectral dependence. Keywords: spectral radiation, desert dust, ultraviolet, aerosol, diffuse irradiance, Bentham (Published: 18 January 2013) Citation: Tellus B 2013, 65 , 19578, http://dx.doi.org/10.3402/tellusb.v65i0.19578
35 citations
Cites methods from "Diffuse UV erythemal radiation expe..."
...Utrillas et al. (2007) reported an averaged diffuse fraction of 0.62 for UVER radiation using data with SZA lower than 708 for the clearest days in Valencia (Spain)....
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TL;DR: In this article, the satellite Ozone Monitoring Instrument (OMI) erythemal daily dose (EDD) product is validated through an intercomparison with ground-based measurements at 14 ground based stations distributed worldwide between 43°N and 64°S in 5 different countries of both hemispheres.
26 citations
TL;DR: A simple sky view factor model is used to examine receipt of UV radiation by a human figure in a vertical position, either standing or sitting, and shows that approximately 34% of the incident horizontal irradiance is not intercepted by the umbrella.
Abstract: A beach umbrella intercepts all direct UV irradiance, but only part of the diffuse component. Using a simple sky view factor model, we have determined the fraction of the hemispheric diffuse irradiance that is not intercepted by the umbrella. Assuming a sensor at the surface and close to the center of the umbrella, isotropic diffuse irradiance and for an umbrella of 80 cm radius and 100 cm high, our results show that approximately 34% of the incident horizontal irradiance is not intercepted by the umbrella. These results agree with irradiance measurements conducted with and without the umbrella. The model is next extended to examine receipt of UV radiation by a human figure in a vertical position, either standing or sitting.
24 citations
TL;DR: In this article, the authors evaluate the NASA EOS AURA Ozone Monitoring Instrument (OMI) UV irradiance estimates through ground-based measurements performed by a NILU-UV multichannel radiometer (NILUUV-UV) operating in Thessaloniki, Greece, for the time period between January 2005 and December 2014.
22 citations
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TL;DR: In this paper, the authors present relationships permitting the determination on a horizontal surface of the instantaneous intensity of diffuse radiation on clear days, the long term average hourly and daily sums of diffuse radii, and the daily sum of diffuse radiata for various categories of days of differing degrees of cloudiness.
2,247 citations
TL;DR: The code is a marriage of a sophisticated discrete ordinate radiative transfer module, low-resolution atmospheric transmission models, and Mie scattering results for light scattering by water droplets and ice crystals that are well suited for a wide variety of atmospheric radiative energy balance and remote sensing studies.
Abstract: SBDART is a software tool that computes plane-parallel radiative transfer in clear and cloudy conditions within the earth's atmosphere and at the surface. All important processes that affect the ultraviolet, visible, and infrared radiation fields are included. The code is a marriage of a sophisticated discrete ordinate radiative transfer module, low-resolution atmospheric transmission models, and Mie scattering results for light scattering by water droplets and ice crystals. The code is well suited for a wide variety of atmospheric radiative energy balance and remote sensing studies. It is designed so that it can be used for case studies as well as sensitivity analysis. For small sets of computations or teaching applications it is available on the World Wide Web with a user-friendly interface. For sensitivity studies requiring many computations it is available by anonymous FTP as a well organized and documented FORTRAN 77 source code.
1,392 citations
"Diffuse UV erythemal radiation expe..." refers methods in this paper
...4.2. Comparison With the Simulated Values From Radiative Transfer Codes [26] The single scattering code SMARTS2.9 [Gueymard, 2001] and the multiple scattering code SBDART2.4 [ Ricchiazzi et al., 1998 ] were used....
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TL;DR: In this article, an upgraded spectral radiation model called SMARTS2 (Simple Model of the Atmospheric Radiative Transfer of Sunshine) is introduced, based on spectral transmittance functions for the main extinction processes in the cloudless atmosphere: Rayleigh scattering, aerosol extinction, and absorption by ozone, uniformly mixed gases, water vapor, and nitrogen dioxide.
745 citations
"Diffuse UV erythemal radiation expe..." refers methods in this paper
...4.2. Comparison With the Simulated Values From Radiative Transfer Codes [26] The single scattering code SMARTS2.9 [ Gueymard, 2001 ] and the multiple scattering code SBDART2.4 [Ricchiazzi et al., 1998] were used....
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Journal Article•
TL;DR: In this article, the authors present relationships permitting the determination on a horizontal surface of the instantaneous intensity of diffuse radiation on clear days, the long term average hourly and daily sums of diffuse radii, and the daily sum of diffuse radiata for various categories of days of differing degrees of cloudiness.
Abstract: Based upon the data now available, this paper presents relationships permitting the determination on a horizontal surface of the instantaneous intensity of diffuse radiation on clear days, the long term average hourly and daily sums of diffuse radiation, and the daily sums of diffuse radiation for various categories of days of differing degrees of cloudiness. For these determinations, it is necessary to have, either from actual measurements or estimates, a knowledge of the total (direct plus diffuse) radiation on a horizontal surface-its measurement is now regularly made at 98 localities in the United States and Canada. For localities where only an estimate of the long term average total radiation is available, relationships presented in this paper can be utilized to determine the statistical distribution of the daily total radiation at these localities.
267 citations
01 Sep 1956
TL;DR: In this paper, the techniques of instrumental measurement and reduction of the records, which have been originated in the Radiation Service of the Union Weather Bureau, are described, and a section is devoted to the problem of correcting for radiation intercepted when shadow bands are employed to screen off the direct solar component.
Abstract: Equipment for the continuous registration, at the earth's surface, of the vertical flux of short-wave sky radiation of solar origin was first introduced into South Africa in 1951. This radiation is the energy component which is scattered out of the solar beam and diffused downwards by gaseous molecules, water droplets and solid particles. A contribution to the radiation from cloudless portions of the sky is also provided by the reflection of sunlight at the surfaces of cloud masses. In this paper the techniques of instrumental measurement and reduction of the records, which have been originated in the Radiation Service of the Union Weather Bureau, are described. In particular, a section is devoted to the problem of correcting for radiation intercepted when shadow bands are employed to screen off the direct solar component. Tabular values of this corrective factor are presented, for a specific screening ring and three standard categories of cloudiness, on a world-wide basis. At present nine radiation stations (soon to be increased to eleven) in Southern Africa are equipped with the type of sky pyranograph described in the paper; in the Belgian Congo, three more stations are operated with equipment which is very similar. The general method outlined here has been adopted by the joint session of the Radiation Commission of the International Union of Geodesy and Geophysics with the Working Group on Radiation of the World Meteorological Organization (Rome 1954) as a basic principle for the introduction of such measurements within national weather services.
150 citations