The validity of a radiative transfer model can be checked either by comparing its results with measurements or with solutions for artificial cases. Unfortunately, neither type of comparison can guarantee that the spectral UV surface irradiance is accurately calculated for real atmospheric cases. There is a need therefore for benchmarks, i.e., standard results that can be used as a validation tool for UV radiation models. In this paper we give such benchmarks for six cloud-free situations. The chosen cases are characterized by different values of solar zenith angle, ozone column, aerosol loading, and surface albedo. Observations are also available for these cases to allow a further comparison between model results and measurements. An intercomparison of 12 numerical models is used to construct the benchmarks. Each model is supplied with identical input data, and a distinction is made between models that assume a plane-parallel geometry and those that use a pseudospherical approximation. Differences remain between the model results, because of different treatments of the input data set. Calculations of direct and global transmission and direct and global irradiance are within 3% for wavelengths longer than 320 nm. For the low-Sun cases the calculations are within 10% for wavelengths longer than 300 nm. On the basis of these calculations, six benchmark UV spectra (295–400 nm) are established with a standard deviation of 2%. Relative standard deviations are higher for the lowest absolute intensities at low Sun (5% at 300 nm). The variation between models is typically less than the variation seen between model and measurement. Differences between the benchmarks and the observed spectra are mainly due to the uncertainty in the input parameters. In four of the six cases the benchmarks agree with the observed spectra within 13% over the whole UV spectral region. © 2000 American Geophysical Union

This paper presents a method for generating surface ultraviolet (UV) radiation maps over Europe, with a spatial resolution of 0.05°, and potentially on a half-hour basis. The UV irradiance is obtained by interpolation in a look-up table (LUT), the entries of which are solar zenith angle, total column ozone amount, cloud liquid water thickness, near-surface horizontal visibility, surface elevation, and UV albedo. Both satellite (Meteosat, GOME) and nonsatellite (synoptic observations, meteorological model results, digital elevation model) data are exploited to assign values to the influencing factors. With the help of another LUT simulating the visible signal, Meteosat data are processed to retrieve the cloud liquid water thickness. The radiative transfer calculations are performed with the UVspec code. A preliminary step consists in generating an effective surface Meteosat albedo map from a series of 10 consecutive days. In this process the well-known difficulty of distinguishing clouds from snow-covered surfaces is encountered. An attempt is made to partially resolve the ambiguity by using the Meteosat infrared channel and modeled snow cover data. After additional empirical cloud filtering, the effective albedo map is used as a baseline to estimate the cloud liquid water thickness. The UV surface albedo is assigned uniform values for land and sea/ocean, except in the presence of snow. In this case it is given a value proportional to the Meteosat effective albedo. The total column ozone is extracted from the level 3 GOME products. The aerosol optical thickness is mapped by gridding the daily measurements performed by ��?1000 ground stations. The digital elevation model is the GTOPO30 data set from the U.S. Geological Survey. European wide UV dose rate maps are presented for one day in April 1997, and the influence of the various factors is illustrated. A daily integrated dose map was also generated using 27 Meteosat acquisitions at half-hour intervals on the same day. The dose map produced in this way takes into account the evolution of the cloud field and is thought to be more accurate than if it were estimated from one data take, in particular at the relatively high spatial resolution of the product. Finally, a preliminary comparison of modeled dose rate and daily dose with measurements performed with a ground instrument is discussed. © 2000 American Geophysical Union

Time series of daily erythemal ultraviolet radiation (UVR) exposure, ozone, and cloud cover were analyzed over the Australian continent using data sets from the NASA Total Ozone Mapping Spectrometer (TOMS) from 1979-1992. The TOMS UVR exposures showed good agreement with data from surface observations. Using a relationship derived from comparisons of the TOMS partial cloud reflectivities with surface cloud cover observations, the TOMS reflectivities were converted into estimates of cloud cover for several Australian regions. It was shown that the deseasonalized time series of UVR exposures can be statistically described as a linear function of ozone and cloud cover anomalies. Results of a trend analysis indicated statistically significant increases in UVR exposures of 10% decade<SUP>-1</SUP> in the summer months in the tropics. These were associated with a simultaneous depletion of ozone and a decrease in cloud cover. Midlatitudinal regions showed no significant trends of UVR. It was found that variations of ozone and UVR over Australia were significantly influenced by the quasi-biennial oscillation (QBO). An increase in zonal wind strength of 20 m s<SUP>-1</SUP> was correlative with reductions of ozone of 1.7% and enhancements of UVR exposures of 2.2%. An increase in solar radio flux of 100�10<SUP>-22</SUP>Wm<SUP>-2</SUP>(Hz)<SUP>-1</SUP> was associated with significant reductions of UVR of 5-10% in the tropical and subtropical regions in summer. The results suggested that enhancements in summer UVR exposures of about 10-20% above the climatological average might be expected in years in which the QBO is in its westerly phase and the solar cycle is at its minimum.

Human exposure to solar ultraviolet radiation has important public health implications. Evidence of harm associated with overexposure to UV has been demonstrated in many studies. Skin cancer and malignant melanoma are among the most severe health effects, but a series of other health effects have been identified. The current report provides a quantification of the global disease burden associated with UV. The information presented forms a knowledge base for the prevention of adverse effects of UV exposure that is achievable with known and accessible interventions. UV prevention focuses on protecting the skin and other organs from UV radiation. On the other hand, a moderate degree of UV exposure is necessary for the production of Vitamin D which is essential for bone health. Additionally, evidence emerges that low Vitamin D levels are likely to be associated with other chronic diseases. Thus, public health policy on ultraviolet radiation needs to aim at preventing the disease burden associated both with excessive and with insufficient UV exposure.

ISBN: 92-807-1724-3

Calcitriol ointment has been approved for the treatment of psoriasis in many countries around the world. It may be prescribed in conjunction with phototherapy. Our purpose was to evaluate the effect of various therapeutic ultraviolet modalities on the stability of calcitriol and, conversely, to study the effects of calcitriol ointment on transmission of different forms of ultraviolet light. Calcitriol ointment 3 microg per g was irradiated with 10 J per cm2 ultraviolet A, 100 mJ per cm2 broadband ultraviolet B, and 3.0 J per cm2 narrowband ultraviolet B, and its stability was compared with samples exposed to fluorescent light and ambient sunlight. Ultraviolet A and ultraviolet B transmission were measured through thin and thick layers of calcitriol 3 microg per g ointment and vehicle. More than 90% of calcitriol ointment is degraded upon exposure to ultraviolet A, broadband ultraviolet B, and narrowband ultraviolet B. Transmission of ultraviolet A is reduced through calcitriol ointment and its vehicle by 17%-31% and 17%-41%, respectively. Transmission of ultraviolet B is reduced by 67%-87% through vehicle and 50%-83% through calcitriol ointment. When used in conjunction with phototherapy, calcitriol ointment should be applied after ultraviolet exposure, not before. Calcipotriene, the only vitamin D analog already approved for psoriasis in the USA, has been used successfully in combination with ultraviolet B and psoralen plus ultraviolet A.

In the United States, there are several federal agencies interested in the effects of UV radiation, which has resulted in the establishment of UV monitoring programs each with their own instrumentation and sites designed to address their specific needs. In 1993, participating agencies of the U.S. Global Change Research Program organized a UV Panel for coordinating the different agencies’ programs in order to ensure that UV data are intercalibrated, have common quality assurance and control procedures, and that the efforts among agencies are not duplicated. In order to achieve these goals, in 1994 the UV Panel recommended formation of the U.S. Central UV Calibration Facility (CUCF), which is operated by the Surface Radiation and Research Branch of the Air Resources Laboratory of National and Oceanic Atmospheric Administration. The CUCF is responsible for characterizing and calibrating UV measuring instruments from several U.S. federal agencies. Part of this effort is to calibrate UVB broadband radiometers from these agencies. The CUCF has three Yankee Environmental Systems (YES UVB-1) and three Solar Light (SL 501A) broadband radiometers as reference standards that are routinely calibrated. For the past three years, clear-sky erythema calibration factors were determined for these standard UVB broadband radiometers by using simultaneously measured erythema-weighted irradiance determined during the annual North American Intercomparison. Comparisons between erythemally weighted irradiance calculated spectra supplied by spectroradiometers typically agreed better than ±2% for solar zenith angles less than 60°. The spectroradiometers were participating in an intercomparison event organized by the National Institute of Standards and Technology and the CUCF. In this article, the calibration methodology is described for transferring the calibration from the spectroradiometers to the CUCF’s standard broadband radiometers. The CUCF standard broadband radiometers are used to calibrate UVB broadband radiometers from several U.S. UV monitoring networks. Erythemal calibration factors for the CUCF’s YES UVB-1 standard broadband radiometer triad are reported for 1994, 1995, and 1996. Erythemal calibration factors for CUCF’s SL 501A standard broadband radiometer triad are reported for 1996.