Erythemal Irradiance Research Articles

Public Health Messages Associated with Low UV Index Values Need Reconsideration.

Overexposure to ultraviolet (UV) radiation is the main modifiable risk factor for skin cancer. The Global Solar Ultraviolet Index (UVI) was introduced as a tool to visualize the intensity of UV radiation on a certain day, which should enable and encourage people to take appropriate protective measures. The ‘low’ exposure category of the UVI, defined by a rounded UVI value of 0, 1 or 2, was linked to the health message ‘No protection required’ by the World Health Organization and partner organizations. However, published evidence corroborating this advice is not available. To evaluate the erythemal risk of low UVI days, we analyzed 14,431 daily time series of ambient erythemal irradiance data measured at nine stations of the German solar UV monitoring network during the years 2007–2016. We analyzed the proportion of days in the sample for which ambient erythemal doses calculated for various time intervals exceed average minimal erythemal doses (MEDs) of the Fitzpatrick skin phototypes I–VI to assess the potential for erythema arising from sun exposure on days with low UVI values. Additionally, we calculated for each day the minimum exposure duration needed to receive one MED. Our results indicate that on days with a UVI value of 0, risk of erythema is indeed negligible. Conversely, the abovementioned health message appears misleading when melano-compromised individuals (skin type I and II) spend more than 1.5 hours outdoors on days with a UVI value of 2. Under rare circumstances of prolonged exposure, MEDs of the two most sensitive skin types can also be exceeded even on days with a UVI value of 1. Hence, current WHO guidance for sun protection on days with low UVI values needs reconsideration.

Erythemal UV Radiation on Days with Low UV Index Values-an Analysis of Data from the German Solar UV Monitoring Network over a Ten-year Period.

According to the World Health Organization and partner organizations, no protection against ultraviolet (UV) radiation is required on days with "low" values (i.e., values <3) of the Global Solar Ultraviolet Index (UVI). Erythemal irradiance (Eer ) data of such days were analyzed to evaluate this claim. Measurements from 9 stations of the German solar UV monitoring network from 2007 to 2016 yielded 14,431 daily Eer time series of low UVI days. Erythemal doses for certain fixed time intervals-acquired from measurements on horizontal planes-were compared with the average minimal erythemal dose (MED) of skin phototype II. Doses from days with rounded UVI values of 0 were insufficient to induce erythema and even on days with rounded UVI values of 1 doses exceeding 1 MED of skin type II could only be acquired under very specific circumstances of prolonged exposure. Conversely, sun exposure on days with rounded UVI values of 2 can indeed provide doses sufficient to induce erythema in skin type II after two hours around noon. In conclusion, our analyses do not support the claim of harmlessness currently associated with the entire low UVI exposure category in public guidance on interpretation of the UVI.

Quantifying the effects of a low-ozone event and shallow stratocumulus clouds on ultraviolet erythemal radiation exposure.

Meteorological and dosimetric ultraviolet (UV) erythemal radiation (UVER) measurements were performed in Didcot, England, on 6 and 7 April 2017. Both days were characterized by clear-sky conditions in the morning and the afternoon with development of shallow stratocumulus clouds (SSC) around noon. In addition, a low-ozone event occurred on 7 April characterized by a 34 DU (Dobson Unit) drop in total stratospheric ozone content. Compared to 6 April, the ozone mini-hole caused UVER increases of 2.67 standard erythema dose (SED) for diffuse and 4.32 SED for global radiation characterized by radiation amplification factors (RAF) of 1.62 and 1.52, respectively. The total global UVER dose reductions due to SSC coverage amount to 2.33 SED (6 April) and 2.81 SED (7 April). As innovation the RAF is decomposed into two parts, named cloud ozone factor (COF) and radiation amplification factor based on measured data (RAFm), to quantify the low-ozone event's effect and the SSC influence in independently modifying the UVER doses. Hereby, the weight of each of these two effects acting during the same low-ozone event is expressed by the new COF. In this case, the COF values range between -0.13 and -0.11 for diffuse UVER and -0.03 to -0.07 for the global UV and UV-B parts. A positive COF value (0.18) results for the global UV-A range.

Statistical Study and Prediction of Variability of Erythemal Ultraviolet Irradiance Solar Values in Valencia, Spain

The goal of this study was to statistically analyse the variability of global irradiance and ultraviolet erythemal (UVER) irradiance and their interrelationships with global and UVER irradiance, global clearness indices and ozone. A prediction of short-term UVER solar irradiance values was also obtained. Extreme values of UVER irradiance were included in the data set, as well as a time series of ultraviolet irradiance variability (UIV). The study period was from 2005 to 2014 and approximately 250,000 readings were taken at 5-min intervals. The effect of the clearness indices on global irradiance variability (GIV) and UIV was also recorded and bi-dimensional distributions were used to gather information on the two measured variables. With regard to daily GIV and UIV, it is also shown that for global clearness index (kt) values lower than 0.6 both global and UVER irradiance had greater variability and that UIV on cloud-free days (kt higher than 0.65) exceeds GIV. To study the dependence between UIV and GIV the χ2 statistical method was used. It can be concluded that there is a 95% probability of a clear dependency between the variabilities. A connection between high kt (corresponding to cloudless days) and low variabilities was found in the analysis of bi-dimensional distributions. Extreme values of UVER irradiance were also analyzed and it was possible to calculate the probable future values of UVER irradiance by extrapolating the values of the adjustment curve obtained from the Gumbel distribution.

Earth Observations from DSCOVR/EPIC Instrument.

The NOAA Deep Space Climate Observatory (DSCOVR) spacecraft was launched on February 11, 2015, and in June 2015 achieved its orbit at the first Lagrange point or L1, 1.5 million km from Earth towards the Sun. There are two NASA Earth observing instruments onboard: the Earth Polychromatic Imaging Camera (EPIC) and the National Institute of Standards and Technology Advanced Radiometer (NISTAR). The purpose of this paper is to describe various capabilities of the DSCOVR/EPIC instrument. EPIC views the entire sunlit Earth from sunrise to sunset at the backscattering direction (scattering angles between 168.5° and 175.5°) with 10 narrowband filters: 317, 325, 340, 388, 443, 552, 680, 688, 764 and 779 nm. We discuss a number of pre-processingsteps necessary for EPIC calibration including the geolocation algorithm and the radiometric calibration for each wavelength channel in terms of EPIC counts/second for conversion to reflectance units. The principal EPIC products are total ozone O3amount, scene reflectivity, erythemal irradiance, UV aerosol properties, sulfur dioxide SO2 for volcanic eruptions, surface spectral reflectance, vegetation properties, and cloud products including cloud height. Finally, we describe the observation of horizontally oriented ice crystals in clouds and the unexpected use of the O2 B-band absorption for vegetation properties.

Irradiancia solar eritémica en Ibarra, Ecuador (ciudad ecuatorial de gran altitud). Mediciones terrestres y satelitales y cálculos con modelos

Irradiancia solar eritémica en Ibarra, Ecuador (ciudad ecuatorial de gran altitud). Mediciones terrestres y satelitales y cálculos con modelos

Synoptic ozone, cloud reflectivity, and erythemal irradiance from sunrise to sunset for the whole earth as viewed by the DSCOVR spacecraft from the earth–sun Lagrange 1 orbit

Abstract. EPIC (Earth Polychromatic Imaging Camera) on board the DSCOVR (Deep Space Climate Observatory) spacecraft is the first earth science instrument located near the earth–sun gravitational plus centrifugal force balance point, Lagrange 1. EPIC measures earth-reflected radiances in 10 wavelength channels ranging from 317.5 to 779.5 nm. Of these channels, four are in the UV range 317.5, 325, 340, and 388 nm, which are used to retrieve O3, 388 nm scene reflectivity (LER: Lambert equivalent reflectivity), SO2, and aerosol properties. These new synoptic quantities are retrieved for the entire sunlit globe from sunrise to sunset multiple times per day as the earth rotates in EPIC's field of view. Retrieved ozone amounts agree with ground-based measurements and satellite data to within 3 %. The ozone amounts and LER are combined to derive the erythemal irradiance for the earth's entire sunlit surface at a nadir resolution of 18 × 18 km2 using a computationally efficient approximation to a radiative transfer calculation of irradiance. The results show very high summertime values of the UV index (UVI) in the Andes and Himalayas (greater than 18), and high values of UVI near the Equator at equinox.

Influence of low ozone episodes on erythemal UV-B radiation in Austria

This study investigates the influence of low ozone episodes on UV-B radiation in Austria during the period 1999 to 2015. To this aim observations of total column ozone (TCO) in the Greater Alpine Region (Arosa, Switzerland; Hohenpeissenberg, Germany; Hradec Kralove, Czech Republic; Sonnblick, Austria), and erythemal UV-B radiation, available from 12 sites of the Austrian UV-B monitoring network, are analyzed. As previous definitions for low ozone episodes are not particularly suited to investigate effects on UV radiation, a novel threshold approach—considering anomalies—is developed to provide a joint framework for the analysis of extremes. TCO and UV extremes are negatively correlated, although modulating effects of sunshine duration impact the robustness of the statistical relationship. Therefore, information on relative sunshine duration (SDrel), available at (or nearby) UV-B monitoring sites, is included as explanatory variable in the analysis. The joint analysis of anomalies of both UV index (UVI) and total ozone (∆UVI, ∆TCO) and SDrel across sites shows that more than 65% of observations with strongly negative ozone anomalies (∆TCO < −1) led to positive UVI anomalies. Considering only days with strongly positive UVI anomaly (∆UVI > 1), we find (across all sites) that about 90% correspond to negative ∆TCO. The remaining 10% of days occurred during fair weather conditions (SDrel ≥ 80%) explaining the appearance of ∆UVI > 1 despite positive TCO anomalies. Further, we introduce an anomaly amplification factor (AAF), which quantifies the expected change of the ∆UVI for a given change in ∆TCO.

Effective cloud optical depth and enhancement effects for broken liquid water clouds in Valencia (Spain)

Partly cloudy skies with liquid water clouds have been analysed, founding that it is essential to distinguish data if the Sun is obstructed or not by clouds. Both cases can be separated considering simultaneously the Cloud Modification Factor (CMF) and the clearness index (kt). For partly cloudy skies and the Sun obstructed the effective cloud optical depth (τ) has been obtained by the minimization method for overcast skies. This method was previously developed by the authors but, in this case, taking into account partial cloud cover. This study has been conducted for the years 2011–2015 with the multiple scattering model SBDART and irradiance measurements for the UV Erythemal Radiation (UVER) and the broadband ranges. Afterwards a statistical analysis of τ has shown that the maximum value is much lower than for overcast skies and there is more discrepancy between the two spectral ranges regarding the results for overcast skies. In order to validate these results the effective cloud optical depth has been correlated with several transmission factors, giving similar fit parameters to those obtained for overcast skies except for the clearness index in the UVER range. As our method is not applicable for partly cloudy skies with the visible Sun, the enhancement of radiation caused by clouds when the Sun is visible has been studied. Results show that the average enhancement CMF values are the same for both ranges although enhancement is more frequent for low cloud cover in the UVER and medium-high cloud cover in the broadband range and it does not depend on the solar zenith angle.

A long term study of the relations between erythemal UV-B irradiance, total ozone column, and aerosol optical depth at central Argentina

Global ultraviolet-B irradiance (UV-B, 280–315nm) measurements made at the campus of the University of Córdoba, Argentina were analyzed to quantify the effects of ozone and aerosols on surface UV-B erythemal irradiance (UVER). The measurements have been carried out with a YES Pyranometer during the period 2000–2013. The effect of ozone and aerosols has been quantified by means of the Radiation Amplification Factor (RAF) and by an aerosol factor (AF, analogous to RAF), respectively. The overall mean RAF under cloudless conditions was (1.2 ± 0.3) %, ranging from 0.67 to 2.10% depending on solar zenith angle (SZA) and on Aerosol Optical Depth (AOD). The RAF increased with the SZA with a clear trend. Similarly, the aerosol effect under almost-constant ozone and SZA showed that, on average, a 1% increase in AOD forced a decrease of (0.15 ± 0.04) % in the UVER, with a range of 0.06 to 0.27 and no defined trend as a function of the SZA. To analyze the effect of absorbing aerosols, an effective single scattering albedo (SSA) was determined by comparing the experimental UVER with calculations carried out with the TUV radiative transfer model.

Solar ultraviolet doses and vitamin D in a northern mid-latitude

Solar ultraviolet (UV) radiation is one of the most important factors in the development of skin cancer in human, solar erythema and skin aging. Nevertheless, numerous studies have shown the benefits of UV solar radiation in moderate doses, such as the reduction of blood pressure and mental health, treatment of various diseases, and the synthesis of vitamin D in the skin.This paper analyses data from solar ultraviolet erythemal (UVER) irradiance in W/m2 measured in a northern mid-latitude as Valencia (Spain) for the period 2003–2010. To estimate effective solar UV radiation in the production of vitamin D (UVD) we used the relationship proposed by McKenzie et al. (2009). It was obtained for one month for each season the minimum exposure time needed around solar noon and at 9 UTC and 15 UTC (Coordinated Universal Time) to obtain the recommended daily dose of 1000IU. Also, it has been calculated time for erythema induction around solar noon for the same months.The median UVER daily dose during the summer months was 4000J/m2day, and 700J/m2day in winter. With regard to UVD, the median UVD daily dose in summer season was 7700J/m2day, and in winter it was 1000J/m2day.Around noon in January it takes more than two hours of solar exposure to obtain the recommended daily dose of vitamin D, whereas the rest of the year range between 7min on July and 31min on October. For the same months around noon, exposure times to produce erythema were obtained, these being of higher value to the previous.The results show that it is difficult to obtain the recommended vitamin D doses in winter in a northern mid-latitude, as the human body is almost entirely covered in this season.

The Long-Term (1964–2014) Variability of Aerosol Optical Thickness and its Impact on Solar Irradiance Based on the Data Taken at Belsk, Poland

Measurements of the Linke turbidity factor (LTF) were performed at Belsk (20.78°E, 51.83°N), Poland, since 1964. This data is used to retrieve broadband aerosol optical thickness normalized to the air mass equal to 2 (BAOT2). A linear analysis of the BAOT2 changes reveals an upward trend of 0.023±0.017(2σ) in the 1964–1975 period, a downward trend of–0.051±0.017(2σ) in the 1976–1991 period, and afterwards a statistically insignificant trend of–0.009 ± 0.014(2σ). Such pattern may be related to the economic changes in Poland (changing emissions and environmental policies). The elevated BAOT2 values, excluded from the trend, are found in 1984 and 1992 due to the volcanic eruptions of El Chichon and Mt. Pinatubo, respectively. Past AOT values at 340 and 500 nm are reconstructed using a linear relationship found between AOT and BAOT2. The reconstructed data is used by the radiative transfer models to estimate a response of the total solar and erythemal radiation to the changes in the atmospheric aerosols at Belsk.

Regulation of the artificial tanning sector in Greece

Introduction The first surveillance action regarding the artificial tanning sector in Greece was recently finalized by the Greek Atomic Energy Commission (EEAE). Results demonstrated noncompliance with the 0.3 W/m 2 erythemal irradiance limit in 65% of the sunbeds measured and inadequate provision of artificial tanning services. Purpose EEAE initiated specific actions in order: (i) to raise public awareness regarding artificial tanning, (ii) to synchronize the artificial tanning sector in Greece with the EU requirements and (iii) to introduce the national legislation for the control and regulation of the artificial tanning sector in Greece, since no relevant national legislation exists. Materials and methods The requirements set by the ELOT EN 60335-2-27:2013, ELOT EN 16489-1:2014, ELOT EN 16489-2:2015 and ELOT EN 16489-3:2015 technical standards as well as the recommendations provided by the EU and international organizations (e.g. WHO, ICNIRP) were used. Results A national code of practice for the provision of the artificial tanning services and an online training course for the sunbeds’ operators were developed. Moreover, informative material was developed in order to raise public awareness regarding the artificial tanning hazards and to guide the users through the approved artificial tanning procedures. Finally, a proposal for the formulation of the upcoming national legislation for the control and regulation of the artificial tanning sector in Greece was introduced. Conclusion Results of the first surveillance action conducted in Greece demonstrated the necessity of regulating the artificial tanning sector and underline the importance of continuing the relevant controls and the public awareness campaigns in Greece. Disclosure Authors disclose that they don’t have any interests or relationships that may bias their presentation.

UVER and UV index at high altitude in Northwestern Argentina

Measurements of ultraviolet erythemal radiation (UVER) made during two years at three sites located at altitudes over 1000ma.s.l. in Northwestern Argentina (Salta, San Carlos, and El Rosal) have been used to estimate and analyze the UV Index (UVI) and the cumulative doses at these locations. For the UVER irradiance, data of January (maximum values) and June (minimum values) have been analyzed as representative of the year for all locations. The UVI reaches extreme (>11) values in >20% of the analyzed days in Salta (1190ma.s.l.), while these are reached in San Carlos (1611ma.s.l.) and El Rosal (3355ma.s.l.) in >40% of the analyzed days. Finally, the cumulative doses over an average year have also been studied for each location. The doses received during austral summer and autumn are of the same order, and represent one third of the annual dose, while the doses received during austral winter and spring represent one sixth of the annual dose approximately.

Outdoor Exposure to Solar Ultraviolet Radiation and Legislation in Brazil.

The total ozone column of 265 ± 11 Dobson Units in the tropical-equatorial zones and 283 ± 16 Dobson Units in the subtropics of Brazil are among the lowest on Earth, and as a result, the prevalence of skin cancer due to solar ultraviolet radiation is among the highest. Daily erythemal doses in Brazil can be over 7,500 J m. Erythemal dose rates on cloudless days of winter and summer are typically about 0.147 W m and 0.332 W m, respectively. However, radiation enhancement events yielded by clouds have been reported with erythemal dose rates of 0.486 W m. Daily doses of the diffuse component of erythemal radiation have been determined with values of 5,053 J m and diffuse erythemal dose rates of 0.312 W m. Unfortunately, Brazilians still behave in ways that lead to overexposure to the sun. The annual personal ultraviolet radiation ambient dose among Brazilian youths can be about 5.3%. Skin cancer in Brazil is prevalent, with annual rates of 31.6% (non-melanoma) and 1.0% (melanoma). Governmental and non-governmental initiatives have been taken to increase public awareness of photoprotection behaviors. Resolution #56 by the Agência Nacional de Vigilância Sanitária has banned tanning devices in Brazil. In addition, Projects of Law (PL), like PL 3730/2004, propose that the Sistema Único de Saúde should distribute sunscreen to members of the public, while PL 4027/2012 proposes that employers should provide outdoor workers with sunscreen during professional outdoor activities. Similar laws have already been passed in some municipalities. These are presented and discussed in this study.

New Approach to Develop Optimized Sunscreens that Enable Cutaneous Vitamin D Formation with Minimal Erythema Risk.

Sunscreens protect the skin against erythemal radiation (Eer). But at the same time they reduce the effective radiation dose (EVD) responsible for the formation of previtamin D in the skin. The paper describes a calculation method for optimizing the ratio EVD/Eer behind sunscreens e.g. with SPF 5, 15 and 30 respectively. Taking into account that a majority of people in industrialized countries suffer from a shortage in vitamin D even in summer time, the ratio Evd/Eer is a new and important criterion for the quality of sunscreens. Furthermore the exposure time tvd needed per day for forming the equivalent of the recommended amount of 2000 IU of vitamin D per day for skin type 2 is estimated when sunscreens with different filter compositions are used. In vitro experiments show a significant increase of the conversion of 7-dehydrocholesterol (7-DHC) to previtamin D when exposed to artificial solar radiation behind an experimental sunscreen optimized for previtamin D production compared to a commercial sunscreen having the same SPF.

Sensitivity of UVER enhancement to broken liquid water clouds: A Monte Carlo approach

AbstractThe study uses a Monte Carlo radiative transfer model to examine the sensitivity of the UV erythemal radiation (UVER) enhancement to broken liquid water clouds of the cumulus and stratocumulus type. The model uses monochromatic radiation at 310 nm corresponding approximately to the peak of the product between irradiance and the erythemal curve. All scattering, absorption, extinction coefficients, and spectral albedos are tuned to this wavelength. In order of importance, fractional cloud cover, the area of individual cloud patches, and cloud thickness exert a strong influence on the enhancement, with smaller contributions from cloud optical depth, cloud base height, and solar zenith angle. In order to produce realistic enhancements for our study area located in the Valencia region of Spain (39°30′N, 0°25′W), measurements were obtained from a Landsat image of the region in combination with a spectral Fourier transform model. The Monte Carlo model, as applied to the Fourier transform cloud distribution, produced satisfactory results compared to 1 year of measured UVER enhancement for the study region provided that fractional cloud cover was equal to or greater than 3/10. At smaller cloud fractions, the neglect of cloud patches less than 50 m × 50 m in area by the model created significant discrepancies.

Sensitivity of UV Erythemal Radiation to Total Ozone Changes under Different Sky Conditions: Results for Granada, Spain.

This study focuses on the analysis of the sensitivity of UV erythemal radiation (UVER) to variations in the total ozone column (TOC) under different sky conditions at Granada (southeastern Spain). The sensitivity is studied both in relative terms by means of the Radiation Amplification Factor (RAF) and in absolute terms using the Ozone Efficiency (OE). These two variables are determined for diverse sky conditions characterized by the cloud cover information given by a sky camera (in oktas) and the cloud optical depth (COD) estimated from global solar radiation measurements. As expected, in absolute terms, the TOC variations cause substantially smaller UVER changes during completely overcast situations than during cloud-free cases. For instance, the OE (SZA = 30°, TOC = 290 DU) decreases from 0.68 mW m(-2) per unit of TOC (0 oktas) to 0.50 mW m(-2) per unit of TOC (8 oktas). However, the opposite is observed when the analysis is performed in relative terms. Thus, the RAF (determined for SZA cases below 80°) increases from 1.1 for cloud-free cases (0 oktas) to 1.4 for completely overcast situations (8 oktas). This opposite behavior is also found when both RAF and OE are analyzed as functions of COD. Thus, while the OE strongly decreases with increasing COD, the RAF increases as COD increases.

Extreme total column ozone events and effects on UV solar radiation at Thessaloniki, Greece

Thirty years of total ozone column (TOC) measurements conducted by a Brewer spectrophotometer, operating in Thessaloniki (40.6°) since March 1982, have been analyzed using the statistical extreme value theory for the identification of extreme TOC events. About 12 % of the total number of days with TOC measurements were identified as extreme-low and ∼15 % as extreme-high events. The influence of the extreme-low events on the annual mean TOC values is up to ∼18 DU, while the extreme-high events show lower impact (up to 12 DU). Removing the extreme events from the time series results in smoother year-to-year variability and reduction of the small long-term linear trend (−0.08 %/year) by a factor of 2. Furthermore, we examined the impact of the extreme events on the noon erythemal irradiance under clear skies, and we provide evidence that even under extreme-low TOC conditions, the UV radiation levels are determined to a great extent by the aerosol optical depth. Although the influence of aerosols is evident during all seasons, for spring and summer, the sensitivity of UV radiation is larger, probably due to the different nature of the aerosols over Thessaloniki during these seasons.

Validation of modeled daily erythemal exposure along tropical and subtropical shipping routes by ship‐based and satellite‐based measurements

AbstractThe Personal ERythemal EXposure (PEREX) model for seafarers working on decks of vessels has been developed to be used for retrospective estimates of personal occupational erythemal exposure in dependence of work profile, time period, and sea route. Extremely high UV index values up to 22 and daily erythemal exposure up to 89 standard erythemal dose have been derived from ship‐based measurements in tropical oceans. Worldwide climatological maps of daily solar erythemal exposure derived from 10 year (2004–2013) hourly grid point radiative transfer model calculations for both cloudless sky and cloudy sky serve as the database of PEREX. The PEREX database is compared with ship‐based measurements taken along four routes of merchant vessels, continuous UV radiation measurements taken on the research vessel Meteor on its mainly tropical and subtropical routes for 2 years, daily cloudless‐sky erythemal exposure derived from 10 min LibRadtran radiative transfer model calculations, and 2 years of satellite‐based erythemal exposure data of the Ozone Monitoring Instrument on the Aura satellite along the ship routes. Systematic differences between PEREX model data, ship‐based data, and satellite‐based daily erythemal exposure for all‐sky conditions are only 1 to 3%, while short‐term variations of cloudiness result in standard deviations of differences around 30%. Measured ratios between cloudless‐sky erythemal radiation at vertical to horizontal incidence decrease with decreasing solar zenith angle, while clouds flatten their diurnal course.