Uncertainties in modeled UV irradiances due to limited accuracy and availability of input data

Schwander, Harry; Koepke, Peter; Ruggaber, A.

doi:10.1029/97jd00244

Cited by 97 publications

(66 citation statements)

References 27 publications

(12 reference statements)

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“…For their instrument they estimate 2σ equivalent uncertainties between 6.3% in the UVA to 12.7% at 300 nm for a solar zenith angle of 60 • . Model simulations also have their uncertainties which have been quantified by Schwander et al (1997) and Weihs and Webb (1997). The uncertainties associated with the simulations are of a similar magnitude to those of the measurements.…”

Section: Single Spectrum (Uvspec)mentioning

confidence: 57%

Technical note: The libRadtran software package for radiative transfer calculations - description and examples of use

2005

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Abstract. The libRadtran software package is a suite of tools for radiative transfer calculations in the Earth's atmosphere. Its main tool is the uvspec program. It may be used to compute radiances, irradiances and actinic fluxes in the solar and terrestrial part of the spectrum. The design of uvspec allows simple problems to be easily solved using defaults and included data, hence making it suitable for educational purposes. At the same time the flexibility in how and what input may be specified makes it a powerful and versatile tool for research tasks. The uvspec tool and additional tools included with libRadtran are described and realistic examples of their use are given. The libRadtran software package is available from http://www.libradtran.org.

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Section: Single Spectrum (Uvspec)mentioning

confidence: 57%

Technical note: The libRadtran software package for radiative transfer calculations - description and examples of use

2005

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“…This corresponds to the strong temperature dependence of the ozone absorption cross section (Molina and Molina, 1986). Further discussion about the dependencies of spectral UV global irradiance on ozone and temperature profiles can be found in Schwander et al (1997). Figure 5 shows two Fig.…”

Section: Op and Tpmentioning

confidence: 99%

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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“…However, the uncertainties in the spatial and temporal variability, the magnitude and the direction of the projected changes of surface UV irradiance are still high . Thus, good quality measurements of the spectral UV irradiance and the main factors controlling its levels at the Earth's surface are of great importance for achieving better understanding and more accurate modelling of the interactions among UV radiation, ozone, aerosols, clouds and surface reflectivity (García et al, 2015;Kreuter et al, 2014;Mayer and Kylling, 2005;Schwander et al, 1997).…”

Section: Fountoulakis Et Al: Short-and Long-term Variability Of Smentioning

confidence: 99%

Short- and long-term variability of spectral solar UV irradiance at Thessaloniki, Greece: effects of changes in aerosols, total ozone and clouds

et al. 2016

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Abstract. In this study, we discuss the short-and the longterm variability of spectral UV irradiance at Thessaloniki, Greece, using a long, quality-controlled data set from two Brewer spectrophotometers. Long-term changes in spectral UV irradiance at 307.5, 324 and 350 nm for the period 1994-2014 are presented for different solar zenith angles and discussed in association with changes in total ozone column (TOC), aerosol optical depth (AOD) and cloudiness observed in the same period. Positive changes in annual mean anomalies of UV irradiance, ranging from 2 to 6 % per decade, have been detected both for clear-and all-sky conditions. The changes are generally greater for larger solar zenith angles and for shorter wavelengths. For clear-skies, these changes are, in most cases, statistically significant at the 95 % confidence limit. Decreases in the aerosol load and weakening of the attenuation by clouds lead to increases in UV irradiance in the summer, of 7-9 % per decade for 64 • solar zenith angle. The increasing TOC in winter counteracts the effect of decreasing AOD for this particular season, leading to small, statistically insignificant, negative long-term changes in irradiance at 307.5 nm. Annual mean UV irradiance levels are increasing from 1994 to 2006 and remain relatively stable thereafter, possibly due to the combined changes in the amount and optical properties of aerosols. However, no statistically significant corresponding turning point has been detected in the long-term changes of AOD. The absence of signatures of changes in AOD in the short-term variability of irradiance in the UV-A may have been caused by changes in the single scattering albedo of aerosols, which may counteract the effects of changes in AOD on irradiance. The anticorrelation between the year-to-year variability of the irradiance at 307.5 nm and TOC is clear and becomes clearer as the AOD decreases.

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Uncertainties in modeled UV irradiances due to limited accuracy and availability of input data

Cited by 97 publications

References 27 publications

Technical note: The libRadtran software package for radiative transfer calculations - description and examples of use

Technical note: The libRadtran software package for radiative transfer calculations - description and examples of use

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

Short- and long-term variability of spectral solar UV irradiance at Thessaloniki, Greece: effects of changes in aerosols, total ozone and clouds

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