Validity of satellite measurements used for the monitoring of UV radiation risk on health (original) (raw)
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2021
This study introduces an Earth observation (EO)based system which is capable of operationally estimating and continuously monitoring the ultraviolet index (UVI) in Europe. UVIOS (i.e., UV-Index Operating System) exploits a synergy of radiative transfer models with high-performance computing and EO data from satellites (Meteosat Second Generation and Meteorological Operational Satellite-B) and retrieval processes (Tropospheric Emission Monitoring Internet Service, Copernicus Atmosphere Monitoring Service and the Global Land Service). It provides a near-real-time nowcasting and short-term forecasting service for UV radiation over Europe. The main atmospheric inputs for the UVI simulations include ozone, clouds and aerosols, while the impacts of ground elevation and surface albedo are also taken into account. The UVIOS output is the UVI at high spatial and temporal resolution (5 km and 15 min, respectively) for Europe (i.e., 1.5 million pixels) in real time. The UVI is empirically related to biologically important UV dose rates, and the reliability of this EO-based solution was verified against groundbased measurements from 17 stations across Europe. Stations are equipped with spectral, broadband or multi-filter instruments and cover a range of topographic and atmospheric conditions. A period of over 1 year of forecasted 15 min retrievals under all-sky conditions was compared with the ground-based measurements. UVIOS forecasts were within ±0.5 of the measured UVI for at least 70 % of the data compared at all stations. For clear-sky conditions the agreement was better than 0.5 UVI for 80 % of the data. A sensitivity analysis of EO inputs and UVIOS outputs was performed in order to quantify the level of uncertainty in the derived products and to identify the covariance between the accuracy of the output and the spatial and temporal resolution and the quality of the inputs. Overall, UVIOS slightly overestimated the UVI due to observational uncertainties in inputs of cloud and aerosol. This service will hopefully contribute to EO capabilities and will assist the provision of operational early warning systems that will help raise awareness among European Union citizens of the health implications of high UVI doses.
Photochemistry and Photobiology, 2014
Cloud effects on UV Index (UVI) and total solar radiation (TR) as a function of cloud cover and sunny conditions (from sky images) as well as of solar zenith angle (SZA) are assessed. These analyses are undertaken for a southernhemisphere mid-latitude site where a 10-years dataset is available. It is confirmed that clouds reduce TR more than UV, in particular for obscured Sun conditions, low cloud fraction (<60%) and large SZA (>60°). Similarly, local shorttime enhancement effects are stronger for TR than for UV, mainly for visible Sun conditions, large cloud fraction and large SZA. Two methods to estimate UVI are developed: (1) from sky imaging cloud cover and sunny conditions, and (2) from TR measurements. Both methods may be used in practical applications, although Method 2 shows overall the best performance, as TR allows considering cloud optical properties. The mean absolute (relative) differences of Method 2 estimations with respect to measured values are 0.17 UVI units (6.7%, for 1 min data) and 0.79 Standard Erythemal Dose (SED) units (3.9%, for daily integrations). Method 1 shows less accurate results but it is still suitable to estimate UVI: mean absolute differences are 0.37 UVI units (15%) and 1.6 SED (8.0%).
Remote. Sens., 2021
Excessive exposure to solar ultraviolet (UV) radiation has damaging effects on life on Earth. High-energy short-wavelength ultraviolet B (UVB) is biologically effective, influencing a range of dermal processes, including the potentially beneficial production of vitamin D. In addition to the damaging effects of UVB, the longer wavelength and more abundant ultraviolet A (UVA) has been shown to be linked to an increased risk of skin cancer. To evaluate this risk requires the monitoring of the solar UVA globally on a time repetitive basis in order to provide an understanding of the environmental solar UVA irradiance and resulting exposures that humans may receive during their normal daily activities. Satellite-based platforms, with the appropriate validation against ground-based instrumentation, can provide global monitoring of the solar UVA environment. Two satellite platforms that currently provide data on the terrestrial UVA environment are the ozone monitoring instrument (OMI) and t...
Improvement of the Valencia region ultraviolet index (UVI) forecasting system
Computers & Geosciences
The CEAM Foundation (Valencia, Spain) has developed an operational ultraviolet index (UVI) forecasting system based in the Santa Barbara DISORT Atmospheric Radiative Transfer (SBDART) model. The main objective of this system is to provide the general public with a tool to minimize the impact of ultraviolet (UV) radiation, which can cause important human health problems. The system presented in this paper has been developed in collaboration with the Environment Department of the Regional Government of Valencia, and it replaces the one running until 2007. The new system substitutes the previously used Ozone Monitoring Instrument (OMI) observed data with the total ozone column data forecasted from the Global Forecasting System (GFS) model. This has allowed the forecasting period to be increased from only one day in the original system to three days, with daily updates. The UVI forecast presented herein uses maps to show the hourly daytime evolution of the UV index on selected locations as well as the maximum UVI expected in the area of interest for the following three days (D, D+1 and D+2). The locations selected correspond to measurement stations equipped with erythemal radiation instruments. The UVI forecast information, the erythemal radiation experimental data and other outreach information are supplied to the public through both the CEAM Meteorology and Climatology Program Web page and the Environment Department of the Regional Government of Valencia Web page.
Empirical models of UV total radiation and cloud effect study
International Journal of Climatology, 2009
Several empirical models of hourly ultraviolet total radiation (UVT) have been proposed in this study. Measurements of UVT radiation, 290-385 nm, have been recorded at ground level from February 2001 to June 2008 in Valladolid, Spain (latitude 41°40 N, longitude 4°50 W and 840 m a.s.l.). The empirical models have emerged due to the lack of some radiometric variables in measuring stations. Hence, good forecasts of them can be obtained from usual measures in these stations. Therefore, some advantages of the empirical models are that they allow the estimation of past missing data in the database and the forecast of future ultraviolet solar availability. In this study, reported models in the bibliography have been assessed and recalibrated. New expressions have been proposed that allow obtaining hourly values of ultraviolet radiation from global radiation measures and parameters as clearness index and relative optical air mass. The accuracy of these models has been assessed through the following statistical indices: mean bias, mean-absolute bias and root-mean-square errors whose values are close to zero, below 7% and below 10%, respectively. Two new clear sky models have been used to evaluate two new parameters: ultraviolet and global cloud modification factors, which can help to understand the role of the clouds on solar radiation. The ultraviolet cloud modification factor depends on cloudiness in such a way that its value under overcast skies is half of the cloudless skies one. Exponential and potential fits are the best relationships between both cloud factors. Finally, these parameters have been used to build new UV empirical models which show low values of the statistical indices mentioned above.
Journal of Geophysical Research, 2000
Assessment of the effects of ozone depletion on biologically effective solar UV at ground level has been greatly advanced through the use of remote sensing data. Satellite data on atmospheric properties allow the construction of geographically distributed surface UV radiation maps based on radiative transfer calculations. In this respect, clouds play a dominant but rather complex role. We compared the reduction of daily UV doses due to clouds, as derived from satellite cloud data, with the reduction derived from routine ground-based measurements of global solar radiation (i.e., broadband total solar irradiances with wavelengths between 0.3 and 2.8 m). An empirical relationship is used to link the reduction due to clouds of global solar radiation and UV radiation. The abundance of global solar radiation measurements (data from over 125 stations in 30 satellite grid cells) for the European region ensured a sound basis for the data analysis for the period considered (May, June, and July of 1990, 1991. Approximately 6500 daily UV-reduction factors, defined as the ratio of daily UV doses calculated with and without clouds, were thus obtained applying both methods. The daily UV-reduction factors (and 10-day averaged UV reduction factors) from the two independent sources correlated well, with r 2 ϭ 0.83 (r 2 ϭ 0.89), and had a standard deviation of 0.06 (0.03). Over 90% of the satellite-derived results agreed within a range of Ϯ0.14 (Ϯ0.07) with the ground-based measurement-derived results. We evaluated sources of uncertainty related to spatial and temporal resolution, and optical properties, and estimated their consequences and range. Among these different sources the largest uncertainties are caused by the sampling error, i.e., grid-cell average versus station average, which is on average 0.10 for daily UV-reduction factors. Information on the atmospheric optical properties during the measurements may reduce the stated range of uncertainty from Ϯ0.14 to Ϯ0.07. The variation of the measurements from station to station is then the limiting factor. We concluded that the reduction of daily UV based on satellite-derived cloud cover and cloud optical thickness relates well with the UV reduction due to clouds derived from ground-based global solar radiation measurements.
Satellite-derived UV irradiances may be the basis for establishing a global UV climatology, provided that their accuracy is confirmed against ground-based (GB) measurements of high quality. In this study, estimates of solar UV irradiance at the surface derived from the Ozone Monitoring Instrument (OMI, onboard the NASA EOS AURA Spacecraft) are compared with GB measurements from two NILU-UV multichannel radiometers of the Greek UV Network (www.uvnet.gr), operating in Athens (38 o N, 23.8 o E) and Thessaloniki (40.6 o N, 23 o E).
Comparison of measured and modelled uv indices for the assessment of health risks
Meteorological Applications, 2001
The World Health Organisation (WHO) and the World Meteorological Organisation (WMO) have jointly recommended that the UV Index (UVI) should be used to inform the public about possible health risks due to overexposure to solar radiation, especially skin damage. To test the current operational status of measuring and modelling techniques used in providing the public with UVI information, this article compares cloudless sky UVIs (measured using five instruments at four locations with different latitudes and climate) with the results of 13 models used in UVI forecasting schemes. For the models, only location, total ozone and solar zenith angle were provided as input parameters. In many cases the agreement is acceptable, i.e. less than 0.5 UVI. Larger differences may originate from instrumental errors and shortcomings in the models and their input parameters. A possible explanation for the differences between models is the treatment of the unknown input parameters, especially aerosols. Copyright © 2001 Royal Meteorological Society
Atmospheric Measurement Techniques Discussions, 2015
Satellite based surface UV product of the Ozone Monitoring Instrument OMI was validated using ground based UV measurements from the two Finnish sites Jokioinen and Sodankylä. The goal was to further investigate the observed positive UV bias of the OMI UV product focusing on how it may be connected to cloudiness during the overpass of the Aura satellite. A total of seven years of summer time data was used to compare OMI UV index to a reference UVI observed on the ground with Solar Light 501 broadband radiometers. Cloudiness during satellite overpass was determined with auxiliary ground based observations on sunshine duration, cloud cover and global radiation as well as the satellite based MODIS cloud cover estimates. The analysis aimed to minimize the error sources from temporal discrepancies and from the differences in the field of view of OMI and its ground based reference data. As a result, OMI UV product was seen to overestimate surface UV index by 21% in average and overcast UV ...
Surface UV from ERS-2/GOME and NOAA/AVHRR data: A case study
Geophysical Research Letters, 1997
A satellite based method for deriving spatial distributions of erythemally weighted UV irradiance at the surface has been developed. The effects of ozone column amount and cloud optical thickness on UV were taken into account by the combined usage of the new European-Space-Agency's GOME (Global-Ozone-Monitoring-Experiment) sensor onboard the European-Research-Satellite-2 (ERS-2) and the NOAA/AVHRR instrument, respectively. As an example for application, horizontal distributions of surface UV irradiances are derived in a region covering the area of Southern Germany on two days 22. July and 13. August 1996. These two days represent clear and cloudy conditions, respectively. For the cloud free day 22. July 1996 the surface UV measurements at Garmisch-Partenkirchen and Hohenpeissenberg (Southern Germany) were about 4.5% lower than those derived from satellite measurements. In addition, the accuracy of the method in case of the cloudy day is discussed. R. Meerkoetter and B. Wissinger, Deutsche Forschungsanstalt ffir Luft-und Raumfahrt (DLR), Institut flit Physik der Atmosph/ire,