UV-related web tools

• FastRT: Fast simulations of downward UV doses, indices and irradiances at the Earth's surface:
  Standard model : https://fastrt.nilu.no/fastrt.html
  Simplified model: https://fastrt.nilu.no/fastrt-ez.html
• VitD_quartMEDandMED: Calculated Ultraviolet Exposure Levels for a Healthy Vitamin D Status and no sunburn:
  Standard model : https://fastrt.nilu.no/VitD_quartMEDandMED_v2.html
  Simplified model: https://fastrt.nilu.no/VitD-ez_quartMEDandMED_v2.html.

FastRT - Fast and easy UV simulation tool

Simulations of ultraviolet irradiances, doses and indices at the Earth's surface at user specified UV wavelengths.

Author: Ola Engelsen
NILU, Norway

Copyright © 2005-2024 NILU

Last modified March 4th 2024.

The current model has undergone internal checking and validation. If you have any questions or comments on this service, please contact NILU (nilu@nilu.no).

If you use this program and publish the results, we would appreciate if you could acknowledge NILU and site:
Engelsen O. and Kylling A., Fast simulation tool for ultraviolet radiation at the Earth's surface. Optical Engineering, 44 (4), 041012 (2005).

FastRT changelog

Introduction

LUT files

• AFGL US standard atmosphere (Anderson et al, 1986)
• The Solar Ultraviolet Spectral Irradance Monitor (SUSIM) extraterrestrial solar spectrum measured on board the Space Shuttle during the ATLAS 3 mission in November 1994 (Van Hoosier, 1996).
• Aerosol angstrom coefficients: α=1.3 (representative for rural aerosols), where the aerosol optical depth = β*λ^-α, where λ is the wavelength is micrometers.
• We assume homogeneous water clouds of user-specified density at 2-7km above ground, droplet radius of 7.2 microns.
• For scattered clouds the computed surface irradiance (E) is a linear combination of the irradiances under a homogeneous cloud cover (E_cloud)) and that under cloudless conditions (E_cloudless), i.e. E = CF * E_cloud + (1-CF)*E_nocloud, where CF is the cloud fraction
• For broken clouds we assume that downward radiation is transmitted as if only a clear atmosphere was present. At the surface all radiation is reflected by the cloudy atmosphere and the surface, i.e., E = E₀T/(1-A*S), where E₀ is the exoterrestrial irradiance, T is the transmittance of a clear atmosphere, S is the albedo of the cloudy atmosphere from below and A is the surface albedo.
• Temperature dependent ozone absorption cross-section: Molina and Molina (1986)
• Aerosol profile: spring/summer (Shettle, 1989)
• Tropospheric aerosol: rural type (from MODTRAN 3)
• Stratospheric aerosol: background conditions (from MODTRAN 3)
• Surface types: The 12 first spectral surface albedos are provided from (Feister and Grewe, 1995), the 6 last spectral surface albedos are provided from (Blumthaler and Ambach, 1988).
• Radiation transfer equation solver: DISORT (Stamnes K et al., 1988)
• Delta-M approximation for forward aerosol scattering.
• Number of radiative streams: 12
• Number of atmospheric layers: 49

The LUT contains effective transmittances (in this case the flux at the surface divided by the extraterrestrial solar flux). The convoluted response is computed by interpolation of the LUT entries.

UV action spectra and doserates

Note that a direct comparison of dose amounts for any induced effect can usually not be made on the basis of action spectrum alone. These spectra normally provide only an indication of the relative biological effectiveness at particular wavelengths, not the actual dose amount required to produce a biological response. In other words, the biological action spectra are usually expressed in relative sensitivities and units rather than absolute ones. The resulting doserates are thus only loosely attached to physical radiation quantities. The use of units with UV doses may thus not be justifiable. The UV doses computed with different action spectra cannot be compared to each other. However, it is meaningful to compare UV doses relative to solar, surface, and atmospheric conditions as they vary with location and time.

Error Analysis

• For a clear sky scenario the error should not exceed 4%. The mean error and its standard deviation are both approximately 1%.
• For a turbid sky with aerosols the error should not exceed 18%. The mean error is 3% and its standard deviation is approximately 4%.
• For a cloudy scenario the error should not exceed 35%. The mean error is 8% and its standard deviation is 9%, approximately. By far the largest errors occur in the special situation when both the surface albedo is large and the ozone column deviates far from 300 DU. This will be improved in the next FastRT version. Note that rather large variabilities in the optical properties of clouds generally occur, constituting a huge uncertainty in UV simulations. The effect of clouds on surface radiation generally much larger than that of aerosols. Currently, FastRT ignores the effect of aerosols when clouds are present.
• For the tests done within the measured UV spectrum diagnosis program CheckUVSpec, we expect that the FastRT error should not exceed 1%.

  

  The figures above show the percent difference of the surface irradiance spectra for a clear sky scenario generated by the FastRT model and the libRadtran model with respect to the latter. The plots illustrate the worst case scenarios. The titles indicate solar zenith angles (sza) in degrees and total ozone columns (ozone) in Dobson units.

  Erythema doserates at clear sky obtained by FastRT and libRadtran models and difference wrt. libRadtran.
  Solar Zenith Angle (deg)	Total Ozone Column (DU)	FastRT	libRadtran (exact)	Percent error
  7.5	130.0	7.683e+02	7.860e+02	2.253
  7.5	310.0	2.793e+02	2.836e+02	1.502
  7.5	490.0	1.624e+02	1.635e+02	0.667
  43.5	130.0	3.492e+02	3.573e+02	2.258
  43.5	310.0	1.252e+02	1.264e+02	0.957
  43.5	490.0	7.473e+01	7.505e+01	0.420
  79.5	130.0	1.439e+01	1.458e+01	1.303
  79.5	310.0	6.124e+00	6.152e+00	0.445
  79.5	490.0	4.433e+00	4.457e+00	0.550

  UV action spectra used in this program

  UV-A
  Unity between 315nm and 400nm. Zero otherwise.

  UV-B
  Unity between 280nm and 315nm. Zero otherwise.

  Erythema (skin burn) action spectrum *)
  McKinlay, A.F. and B.L. Diffey, 1987: A reference action spectrum for ultraviolet induced erythema in human skin. CIE Research Note, CIE-Journal, Vol. 6, No.1(17-22).

  This action spectrum is now accepted as the reference erythemal spectrum by the International Lighting Commission (CIE).

  DNA (skin cancer) action spectrum *)
  Setlow, R.B., 1974: The wavelengths in sunlight effective in producing skin cancer: A theoretical analysis. Proc.Natl.Acad.Sci., U.S.A. 71:3363-3366.

  ACGIH action spectrum *)
  ACGIH, 1990: Treshold limit values and biological exposure indices for 1990-1991. American Conference of Governmental Industrial Hygienists (ACGIH), Cincinnati, Ohio, USA. Proposed sensor for effective UV-irradiance for the monitoring of both natural and artificial weathering conditions

  POLY (polymer degradation) action spectrum
  Proposed sensor for effective UV-irradiance for the monitoring of both natural and artificial weathering conditions
  Wachtendorf, V., Geburtig, A., Trubiroha, P., 9th European Weathering Symposium: Natural and Artificial Ageing of Polymers. Ed Th. Reichert, CEEES-Publication No. 19/2019, ISBN978-3-9818507-5-8, p. 293 - 306

  SCUP *) / SCUP-M ^) / SCUP-H ACTION SPECTRA ^)
  de Gruijl, F.R. and J.C. van der Leun, 1994: Estimate of the wavelength dependency of ultraviolet carcinogenesis in humans and its relevance to the risk assessment of a stratospheric ozone depletion. Health Phys., vol 67, 319-325.

  PRT (DNA to protein crosslinks) action spectrum *)
  M.J. Peak and J.G. Peak, "DNA-to-protein crosslinks and backbone breaks caused by far- and near-ultraviolet, and visible radiations in mammalian cells". In Mechanisms of DNA Damage and Repair. Implications for Carcinogenesis and Risk Assessment, (Edited by M.G. Simic, L. Grossman and A.C. Upton), pp 193-202, Plenum Press, New York, 1986

  SSB (DNA breaks) action spectrum *)
  M.J. Peak, J.G. Peak and B.A. Carnes, "Introduction of direct and indirect single-strand breaks in human cell DNA by far- and near-ultraviolet radiations: Action spectrum and mechanisms." Photocem. Photobiol., 45, pp.381-387, 1987

  Cod egg mortality action spectrum !)
  Kouwenberg, J.H.M., H. I. Browman, J. A. Runge, Biological weighting of ultraviolet (280-400 nm) induced mortality in marine zooplankton and fish. I. Atlantic cod (Gadus Morhua) eggs, Marine Biology, 134 (2), 269-284, 1999.

  Calanus Finmarchicus mortality action spectrum !)
  Kouwenberg, J.H.M., H. I. Browman, J.-F. St-Pierre, Biological weighting of ultraviolet (280-400 nm) induced mortality in marine zooplankton and fish. II. Calanus Finmarchicus (Copepoda) eggs, Marine Biology, 134 (2), 285-293, 1999.

  Vitamin D action spectrum +)
  Holick, M, R. Bouillon, J. Eisman, M. Garabedian, J. Kleinschmidt, T. Suda, I. Terenetskaya, A. Webb. CIE Technical Committee 6-54 Technical Report 174 (2006) Action spectrum for production of previtamin D3 in human skin. Commission Internationale de l'Eclairage (CIE) Central Bureau. Vienna, Austria, email: ciecb@ping.at

  Vitamin D action spectrum (old version)
  MacLaughlin JA, Anderson RR, Holick MF. Spectral character of sunlight modulates the photosynthesis of previtamin D₃ and its photoisomers in human skin. Science. 1982; 1001-1003. The action spectrum has been normalized to unity at 295 nm. Beyond 315 nm, the action spectrum was extrapolated by an exponential decay function.

  POL (polychromatic actions spectrum for higher plants) *)
  M.M. Caldwell, L.B. Camp, C.W. Warner and S.D. Flint, "Action spectra and their key role in assessing biological consequences of solar UV-B radiation", In Stratospheric Ozone Reduction, Solar Ultraviolet Radiation and Plant Life, Worrest   Caldwell (eds.), pp.87-111, Springer, Heidelberg, 1986

  PTP (phytoplankton photoinhibition) action spectrum *)
  Mitchell, B.G., "Action Spectra for ultraviolet photoinhibition of Antarctic phytoplankton and a model of spectral diffuse attenuation coefficients", In Response of Marine Phytoplankton to Natural Variations in UV-B Flux, (Edited by G. Mitchell, I. Sobolev and O. Holm-Hansen), Proc. of Workshop, Scripps Institution of Oceanography, La Jolla, CA, April 5, 1990

  PTP2 (Prorocentrum) and PTP3 (Phaeodactylum) action spectrum *)
  Cullen, J. J., P. J. Neale and M. P. Lesser, 1992: Biological weighting function for the inhibition of phytoplankton photosynthesis by ultraviolet radiation. Science. 258, 646-650.

  TYP (typhimurium killing) action spectrum *)
  McKay, D., A. Eisenstark, R.B. Webb and S. Brown, "Action spectra for lethality in recombinationless strains of Salmonella typhimurium and Escherichia coli", Photochem. Photobiol., 24, pp.337-343, 1976

  Plant Damage Action Spectrum *)
  ATTENTION! Plant response is normalised at 300 nm.
  Caldwell, M.M., L.B. Camp, C.W. Warner, S.D. Flint, 1986: Action spectra and their key role in assessing biological consequences of solar UV-B radiation change. In: Worrest, R.C. and M.M. Caldwell (Eds.): Stratospheric ozone reduction, solar ultraviolet radiation and plant life. Springer-Verlag, Berlin. p.87-111.

  Mammalian Non-melanoma Skin Cancer Action Spectrum ^)
  de Gruijl, F.R. and J.C. van der Leun. 1994. Estimate of the wavelength dependency of ultraviolet cacinogenesis in humans and its relevance to the risk assessment of stratospheric ozone depletion. Health Physics, 67: 319-325.

  Erythemal (skin burn) Action Spectrum 2 ^)
  McKinlay, A.F. and B.L. Diffey. 1987. A reference action spectrum for ultra-violet induced erythema in human skin. In Human Exposure to Ultraviolet Radiation: Risks and Regulations. W.F. Passchier and B.F.M. Bosnjakovich, eds. International Congress Series. pp. 83-87.

  DNA Damage Action Spectrum ^)
  Setlow, R.B. 1974. The wavelengths in sunlight effective in producing cancer: a theoretical analysis. Proceedings of the National Academy of Sciences U.S.A., 71: 3363-3366.

  Melanoma Induction in Platyfish-swordtail Hybrids Action Spectrum ^)
  Setlow, R.B., E. Grist, K. Thompson, and A.D. Woodhead. 1993. Wavelengths effective in induction of malignant melanoma. Proceedings of the National Academy of Sciences U.S.A., 90: 6666-6670.

  UV-Index (WMO)
  World Meteorological Organization (WMO), Report of the WMO Meeting of Experts on UV-B Measurements, Data Quality and Standardization of UV Indices, World Meteorological Organization Global Atmosphere Watch, Report No. 95, 1994

  United States Environmental Protection Agency, Office of Air and Radiation, Stratospheric Protection Division, 6205-J, EPA 430-H-94-003, February 1995, URL: http://www.cpc.ncep.noaa.gov/products/stratosphere/uv_index/uv_compute.shtml

  ---

  *) Courtesy of Dr. Tapani Koskela, Finnish Meteorological Institute, Helsinki, Finland

  Main source:
  Morys M. and D.Berger, 1993: The accurate measurements of biologically effective ultraviolet radiation. SPIE Proc. Vol.2049, Atmospheric Radiation, pp. 152-161.

  ^) Courtesy of Dr. Darryl H Charache, Consortium for International Earth Science Information Network (CIESIN), MI 48710, USA

  +) Courtesy of Ann Webb, University of Manchester, Exponential decay extrapolation beyond 315 nm

  !) Courtesy of Dr. Ralf Meerkoetter, DLR-Institut fuer Physik der Atmosphaere, Oberpfaffenhofen, D-82234 Wessling, Germany

  References

  Mayer, B., G. Seckmeyer and A. Kylling, Systematic longterm comparison of spectral UV measurements and UVSPEC modeling results, Journal of Geophysical Research, 102, 8755-8767, 1997.

  Kylling A, Stamnes K and Tsay S C: "A reliable and efficient two-stream algorithm algorithm for spherical radiative transfer: Documentation of accuracy in realistic media", J. Atm. Chem., 21, 115-150, 1995

  Anderson G P, Clough S A, Kneizys F X, Chetwynd J H, Shettle E P, AFGL atmospheric constituent profiles (0-120km), Tech. Rep. AFGL-TR-86-0110, Air Force Geophys. Lab., Hascom Air Force Base, Mass., 1986

  Van Hoosier, 1996, ftp susim.nrl.navy.mil, cd pub.uars

  Molina and Molina, Journal of Geophysical Research, vol. 91, pp 14501-14508, 1986

  Shettle E P, "Models of aerosols, clouds and precipitation for atmospheric propagation studies, In Atmospheric propagation in the UV, visible, IR and MM-region and related system aspects, AGARD Conf. Proc. pp. 15-1-15-13, 1989

  Stamnes K, Tsay S C, Wiscombe W and Jayaweera K, "A numerically stable algorithm for discrete ordinate method radiative transfer in multiple scattering and emitting layered media, Applied Optics, 27, 2502-2509, 1988

  Dahlback A and Stamnes K, "A new spherical model for computing the radiation field available for photolysis and heating at twilight", Planet. Space Sci., 39, 671-683, 1991

  U. Feister and R. Grewe, Spectral albedo measurements in the UV and visible region over different types of surfaces, Photochemistry and Photobiology, 62, 736-744, 1995.

  M. Blumthaler and W. Ambach, Solar UVB-Albedo of various surfaces, Photochemistry and Photobiology, 48, 1, pp. 85-88, 1988