Erythemally Weighted Radiometers in Solar UV Monitoring: Results from the WMO/STUK Intercomparison

Leszczynski, Kirsti; Jokela, Kari; Ylianttila, Lasse; Visuri, Reijo; Blumthaler, M.

doi:10.1562/0031-8655(1998)067<0212:ewrisu>2.3.co;2

Cited by 86 publications

(38 citation statements)

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“…This information was combined with direct and diffuse irradiances computed from a radiative transfer code (13) assuming a hemispherically isotropic scattered radiation field. Errors introduced by the assumption of hemispheric isotropy are estimated to be less than 4% (14)(15)(16). We computed the ratio of direct to total horizontal irradiance as a function of SZA and column ozone amount.…”

Section: ϫ2mentioning

confidence: 99%

Annual and Interannual Behavior of Solar Ultraviolet Irradiance Revealed by Broadband Measurements¶

Frederick

Slusser

Bigelow

2007

Photochemistry and Photobiology

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This research examines the behavior of ground-level solar UV radiation as measured by eight broadband meters in the continental United States during the period from late 1994 to late 1998. The goal is to define the variability that occurs in UV irradiance over time scales ranging from one to several years. The monthly integrated irradiances, from latitude 32؇N to 47؇N, contain large annual cycles and latitudinal gradients which depend on season. Seven of the eight sites show a maximum in July, a behavior related to proximity to the summer solstice, with modifications associated with the annual cycle in column ozone. A large interannual variability in monthly integrated irradiance appears over the 4 year period studied. A comparison of corresponding months during different years shows differences in irradiance of 20% or more in one-third of the cases analyzed. When the solar zenith angle (SZA) is held fixed in the range 60-65؇, a substantial annual cycle in UV irradiance remains where the maximum monthly mean irradiance is 1.4-1.9 times the minimum, depending on location. Furthermore, the annual cycle at fixed SZA is not in phase with the normal seasonal cycle. Maximum irradiances at fixed SZA tend to occur in the October to December period, while minima cluster in April through July. The annual cycle in ozone, with maximum column values in spring and minima in autumn, explains the general character of the fixed-SZA data, although changes in cloudiness are significant contributors to interannual variability.

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Section: ϫ2mentioning

confidence: 99%

Annual and Interannual Behavior of Solar Ultraviolet Irradiance Revealed by Broadband Measurements¶

Frederick

Slusser

Bigelow

2007

Photochemistry and Photobiology

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“…The absolute calibration was performed in an intercomparison of several spectroradiometers and the ELDONET instrument in September 1997 in Garmisch-Partenkirchen (southern Germany). Intercomparison of instruments to measure solar radiation is a vital tool for quality control and documentation (Seckmeyer et al 1994;Leszczynski et al 1998). All instruments are recalibrated at least every year.…”

Section: Calibrationmentioning

confidence: 99%

European light dosimeter network (ELDONET): 1998 data

et al. 2001

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“…With the former, the exact erythemal function from the CIE (Commission Internacionale de l'Eclairage) (McKinlay and Diffey, 1987) can be applied to the spectral measurements to obtain the erythemal UV irradiance and UVI. In contrast, the spectral response of UV radiometers deviates from the CIE response, which can lead to large uncertainties in the measured UVI (Leszczynski et al, 1998). Several intercomparison campaigns have shown agreements that can be expected between different instruments.…”

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Towards closure between measured and modelled UV under clear skies at four diverse sites

et al. 2007

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Abstract. The purpose of this work is determine the extent of closure between measurements and models of UV irradiances at diverse sites using state of the art instruments, models, and the best available data as inputs to the models. These include information about aerosol optical depth (unfortunately not extending down as far into the UVB region as desirable because such information is not generally available), ozone column amounts, as well as vertical profiles of temperature. We concentrate on clear-sky irradiances, and report the results in terms of UV Index (UVI).Clear-sky data from one year of measurements at each of four diverse sites (Lauder -New Zealand, Mauna Loa Observatory -Hawaii, Boulder -Colorado, and Melbourne -Australia) have been analysed in detail, also taking account of different measurements of ozone, including satellite-derived values, as well as ground measured values, both from Dobson instruments and as retrieved from the UV spectra under study. Previous studies have generally focussed on data from a single site, and for shorter periods. As such, it is the most comprehensive study of its kind to date.At Lauder, which is the cleanest low altitude site, we obtained agreement between measurement and model at 5% level, which is consistent with the best agreement found previously. At Mauna Loa Observatory, similar agreement was achieved, but model calculations need to allow for reflections from cloud that are present below the observatory. At this site, there are occasional problems with using satellitederived ozone. At Boulder, mean agreements were similar but the dispersion around the mean was slightly larger, corresponding to larger uncertainties in the aerosol inputs to the model. However, at Melbourne, which is the only nonCorrespondence to: J. Badosa (jordi.badosa@gmail.com) NDACC (Network for the Detection of Atmospheric Composition Change) site, there remain unexplained discrepancies.The measured values are significantly lower than the calculated values. We investigate the extent to which this discrepancy can be explained by incomplete knowledge of aerosol extinctions in the UV at this site. We conclude that further information about aerosol optical depth and single scattering albedo in the UVB region is needed to resolve the issues. For more polluted sites (the four considered locations show in general small aerosol load), the uncertainties in the aerosol input parameters would lead to less confidence on the modelling approach. At the three NDACC sites, the closure provided by the study gives confidence in both the measurements and our ability to model them. This study revealed a limitation in the use of PTFE diffusers when temperatures are lower than approximately 20 • C. It also documents the range of clear sky UVI values expected at these diverse sites.

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Erythemally Weighted Radiometers in Solar UV Monitoring: Results from the WMO/STUK Intercomparison

Cited by 86 publications

References 0 publications

Annual and Interannual Behavior of Solar Ultraviolet Irradiance Revealed by Broadband Measurements¶

Annual and Interannual Behavior of Solar Ultraviolet Irradiance Revealed by Broadband Measurements¶

European light dosimeter network (ELDONET): 1998 data

Towards closure between measured and modelled UV under clear skies at four diverse sites

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