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Australian UV and Ozone Forecasting System



L.Lemus-Deschamps, S.Grainger, L.Rikus and R.Dare

CAWCR, Bureau of Meteorology, Melbourne Victoria, Australia.

Last Updated February 2008
The experimental results are produced as a research result of interest to other researchers and they are not associated with the operational products and services of the Bureau. The copyright declaration.



Abstract

To alert people of possible high levels of ultraviolet (UV) radiation, UV forecast is issued daily by the Bureau of Meteorology. The UV forecast is important because approximately 380,000 Australians still get skin cancer every year. The UV forecast is based on analysis and forecast of total ozone using satellite radiances and total ozone. The analysed ozone field is mapped to potential vorticity, and advected using the weather forecast model fields. The resulting total ozone fields, and the meteorological fields, are then use in a two stream delta-Eddington radiation code to generate global and Australian UV fields. To further rise awareness of the dangers of overexposure to UV radiation, UV Alert forecast has been included in the weather report with a sun protection message. The UV forecast is released to the public by the Bureau of Meteorology regional office in each state. It is provided to the media as part weather report, and is used in Australia SunSmart's promotional and educational campaigns. The ozone analyses and forecasts are used by a number of groups to issue statements on the development of the ozone hole each year. Upgrades to The UV and Ozone Forecasting System, and comparison of Ozone and UV,analysis and forecast, with satellite and surface measurements is presented here.


The UV and Ozone Forecasting System

a) UV Index and UV Alert

The Australian UV and Ozone Forecasting system supports the Australian UV Index, UV Alert and Ozone forecast issued daily by the Bureau of Meteorology as part of the weather report. The Australian UV and Ozone Forecast system (Lemus-Deschamps et al., 1999) computes global fields of UV with a two-stream delta-Eddington radiation code, using the meteorological fields from the Bureau of Meteorology's operational global numerical weather prediction model "GASP" (Bourke et al., 1995), and total ozone from an offline ozone analysis and forecast scheme.

The standard erythemal action-spectrum from McKinlay and Diffey (1987) is used in the UV and Ozone system to represent the sensitivity of human skin to specific UV radiation. The instantaneous skin damage caused by UV radiation (dose-rate) is obtained from the product of the UV incident at the surface and the erythemal action spectrum integrated over wavelength. This defines the erythemally weighted dose-rate, and is given in terms of a dimensionless UV Index (WMO, 1995). One UV Index unit is equal to 25 mW/m2. A qualitative "danger category" has been associated to the UV Index; values below 3 units are considered low and equal to or greater than 11 are considered extreme.

The UV Index is calculated for clear skies, at local solar noon, when the sun is at its highest, using total ozone analyses and forecasts derived from satellite data and GASP wind fields. Initially a simple parameterization for the extraterrestrial solar irradiance, and a simple exponential fit to ozone absorption cross sections data was adopted. The surface albedo assumed was to be 0.02. Which was a reasonable value for Australian conditions, though no allowance was made for aerosol scattering or absorption (Lemus-Deschamps et al., 1999). The UV Index was calculated for the wavelength interval from 290 to 340nm in 1nm intervals. Cloud effects were included by multiplying the clear sky UV Index by a cloud factor, which is prescribed for different cloud conditions. The cloud factor was derived from the erythemal dose and cloud cover data presented by Paltridge and Barton (1978).

In the next development stage, the extraterrestrial solar irradiance from ATLAS (Wood et al., 1996) and UV surface albedo climatology from TOMS (Herman et al, 1997) were implemented. Rayleigh scattering (Teillet al., 1990), and the Molina and Molina (1986) ozone cross sections were also implemented. Aerosols were included following a similar approach to the one used in UVSPEC (Stamnes et al., 1988, Killyng et al., 1998), and the integration wavelength interval was extended to 400nm. Currently the Australian region is extracted from the global clear sky UV Index and daily UVdose (kJ/ m2) fields (Lemus-Deschamps et al., 2004).

Diurnal clear-sky UV Index for all the Bureau of Meteorology forecasting sites. Global cloudy UVdose and UV Index are derived using forecast clouds amounts from GASP, and are available at the BMRC internal Web page. A UV Alert is issued when the UV Index forecast is three or above. It indicates the times when people need to implement some sun protection behaviour. The UV Alert combined with the SunSmart brand was implemented as part of the Bureau of Meteorology weather report, on December 2005 (Deschamps et al, 2006; Lemus_Deschamps et al., 2006). The UV Index and Alert forecast, combined with the SunSmart brand, is the result of the collaboration program between the Bureau of Meteorology, the Cancer Council Australia and The Australian Radiation Protection and Nuclear Safety Agency (ARPANSA). UV Forecasts are continuously compared with ARPANSA surface measurements as part of the ongoing collaboration program between Bureau of Metorology and ARPANSA.


b) Ozone

Total ozone analyses were initially generated from a single variable statistical interpolation analysis scheme (Grainger, 1998) utilizing data from NESDIS (NOAA14) TOVS total ozone retrieval. Total ozone forecasts are produced from the analyses by assuming that the bulk of the ozone lies in a thick layer, and then advecting that layer using the forecast isentropic wind and pressure thickness at the appropriate level,from the weather forecast model GASP. The vertical distribution of the ozone at each grid point is taken from a zonal ozone climatology weighted to reproduce the analysed or forecast total ozone (Atkinson et al, 1997).

In the next stage, NOAA15, and then NOAA16 were included and the NESDIS total ozone retrieval replaced by the direct assimilation of NOAA16 total ozone amounts. Direct assimilation of NOAA15 and NOAA16 total ozone amounts were performed. The effective isentrope level has been changed to 380K and TOMS total ozone used to initialise the ozone analysis and forecast scheme. After a 6 months parallel trial the assimilation of blended total ozone from NOAA15-NOAA16 and TOMS was implemented in the UV and Ozone system. Which became operational in July 2003. Verification of the global total ozone amounts against TOMS ozone data is performed daily and it is available at the BMRC internal Web page.

Currently, after a lengthy parallel trial, a modified NESDIS total ozone retrieval (Neuendorffer,1996) is used to derive the total ozone amounts from the NOAA16 and NOAA17 radiances. When available, OMI total ozone is "blended-nudged" to produce the ozone forecast. The original UV and Ozone forecast system resolution of 2.5x2.5 degrees with 29 vertical levels, has been upgraded to 240 longitudes, 120 latitudes, and 60 vertical levels (T79L60) (Lemus-Deschamps et al., 2007). Comparison with satellite data is performed daily.


c) Validation

Verification of cloudy sky UVdose against TOMS UVdose data was performed daily and it was available at the BMRC internal Web page. It will be implemented when OMI UVdose becames available. Model UV Index is regularly compared against (ARPANSA) ground-based, as part of the ongoing collaboration project, results have been preseted in Gies et al.(2004), Lemus-Deschamps et al.(2004) Lemus-Deschamps et al.(2006), Deschamps et al. (2006), Lemus-Deschamps (2007).

A comparison of clear and cloudy sky UV Index annual cycle with surface measurements for several Autralian cities is presented by Lemus-Deschamps et al. (2004). In this paper an Australian Climatology (1997-2001) of; annual, seasonal, and monthly averages, of clear and cloudy sky UV Index and UV dose is presented. Ozone climatology is also included.

Examples of the daily maps of the operational Australian UV Index forecast are available on the BoM Website: http://www.bom.gov.au/weather/uv: UV Index Map
The UV Index diurnal cycle and UV Alert are available at http://www.bom.gov.au/weather/national/charts/UV.shtml: UV Index and UV Alert Forecast
Daily global UV Index and Ozone comparisons with TOMS can be found at the Bureau of Meteorology Research Centre Experimental results Web page.

Operational products:
UV Index information
UV Index Forecast
Forecast for Selected Locations
Daily UV Index for several Australian Cities

Experimental results:
Daily comparison of Global distribution of UV Index analysis/forecast, ozone analysis/forecast and cloudy UV dose with satellite data are available the Bureau of Meteorology Research Centre Experimental results Web page and at the BMRC internal Web page. Also included is the Southern Hemisphere ozone hole outlook.
EXP:SH Ozone (model and TOMS) and GASP 50hPa temperature
EXP:Global clear-sky UV Index, Ozone and clear and cloudy sky UVdose from model and TOMS data set
EXP:Southern Polar Ozone from model

Report on the meteorological conditions of the Southern Hemisphere Ozone hole can be found at the BMRC Research Letters http://www.bom.gov.au/bmrc/pubs/researchletter.htm : BMRC Res.Lett. (No1 to No7) and at the BMRC Web Experimental and internal Web pages.


d) UV Index and UV Alert Reporting

From December 2002, the Bureau of Meteorology, Cancer Council Australia, and The Australian Radiation Protection and Nuclear Safety Agency adopted the World Health Organisation (WHO, 2002) UV Index colour standard for reporting the level of UV danger in Australia (Dixon et al., 2002). The danger cathegory adopted is LOW (1-2 UV Index units), MODERATE(3-5 UV Index units), HIGH (6-7 UV Index units), VERY HIGH (8-10 UV Index units) and EXTREME (equal to or greater than 11 UV Index units).

To further simplify and standardise the presentation of the UV Index to the public, the UV alert forecast combined with the SunSmart logo is issued by the Bureau of Meteorology as part of daily weather report. It is expected that the UV Alert combined with the SunSmart logo will encourage people to "be SunSmart" and undertake some protection behaviours. The UV Alert forecast combined with the SunSmart brand is a joint initiative of the Bureau of Meteorology, The Cancer Council Australia and ARPANSA (Deschamps et al., 2006; Lemus-Deschamps et al.,2006).
The UV Index and UV Alert forecast are released to the public by the Bureau of Meteorology regional office in each state. The forecast is provided to the media as part of the Bureau of Meteorology weather report, and it is also available at the Bureau of Meteorology web page, http://www.bom.gov.au/weather/uv, with more than 15000 visits a month.


The UV Index and Ozone forecast system has been made possible by the strong collaboration between different groups of; the Bureau of Meteorology, the Cooperative Research Centre for Southern Meteorology, the Australian Radiation Protection and Nuclear Safety Agency, and The Cancer Council Australia. We thank G. Stephens and R.Atkinson for his work on the original system. ARPANSA providing the UV Index surface measurements. The Bureau of Meteorology NMOC 's staff for their ongoing support to the operational system. Radiances and total ozone amounts from NOAA/NESDIS are used as input to the model. The OMI are also used in the forecast system, and they are freely available at their web page.


References

Atkinson, R., Grainger, S. and P.M. Udelhofen, 1997: A scheme for the routine analysis and deterministic prediction of the global total ozone distribution. In Proceedings of AMS International Conference on the Meteorology of the Southern Hemisphere, Pretoria, Africa.

Bourke, W., T. Hart, P. Steinle, R. Seaman, G. Embery, M. Naugton, and L. Rikus, 1995: Evolution of the Bureau of Meteorology global assimilation and prediction system. Part1: Analysis and Initialisation. Aust. Met. Mag., 44, 19-40.

Grainger, S., 1998: Global analysis of ozone by statistical interpolation of satellite data. PhD Thesis, 182pp, Monash University, Melbourne Australia.

Dixon, H., L. Lemus-Deschamps and P. Gies, 2002: Meteorology meets public health: UV forecasts and reports for sun safety. Health PromotionJournal of Australia,13 (3), 252.

Gies, P.,Colin Roy, John Javorniczky, Stuart Henderson, Lilia Lemus-Deschamps, and Colin Driscoll, 2004: Global Solar UV Index: Australian Measurements, Forecasts and Comparison with the UK. Photochem.Photobiol.79(1), 32-39.

Herman, J.R. and E.A. Celarier, 1997: Earth surface reflectivity climatology at 340-380nm from TOMS data. J. Geophys. Res., 102, 28,003-28,011.

Killyng, A., and G. Seckmeyer, 1998: Libradtran, Library for radiative transfer calculations, Edition 1. For libRadtran Version 0.4.

Lemus-Deschamps L., 2007: The Ozone and UV Forecasting System, Presented at the AMOS Conference, Adelaide, Australia, February 2007.

Deschamps L., P. Gies, L. Rikus, R. Dare and K. Strong, 2006: UV Index for Sun Safety. BMRC Res.Lett. No4, 34-35.

Lemus-Deschamps, L., P. Gies, L. Rikus, K. Strong and H. Dixon, 2006: UV Index: Forecasts and Media Weather Reports. UV Radiation and its Effects, Report of the NIWA Workshop, Dunedin, New Zealand, April 2006. RSNZ,Miscellaneous series 68,25-26.

Lemus-Deschamps L., L.Rikus, S.Grainger, P.Gies, J.Sisson and Z.Li, 2004: UV index and daily total UV dose distributions for Australia (1997-2001). Aust.Met.Mag. 53,239-250.

L.Deschamps, G.Roff, P.Fraser, A.Klekociuk and S.Grainger, 2004: Ozone and UV September 2004. BMRC Res.Lett. No1.,1-4.

Lemus-Deschamps Lilia, Lawrie Rikus and Peter Gies, 1999: The operational Australian ultraviolet index forecast 1997. Meteorol. Appl. 6, 241-251.

Mills Frankiln P., Lilia Lemus-Deschamps, Stephen R. Wilson, 2004: Impact of Extreme Temperature ustralian Measurements, Forecasts and Comparison with the UK. AMS Conference, August,2004.

Molina, L.T., and M.J. Molina, 1986: Absolute absorption cross sections of ozone in the 185-to 350nm wavelength range. J. Geophys. Res. 91, No D13, 14501-14508.

McKinlay, A.F., and B.L. Diffey, 1987: A reference action spectrum for ultraviolet induced erythema in human skin. In Human Exposure to Ultraviolet Radiation: Risks and Regulations (W.R. Passchler and B.F.M. Bosnajokovic, eds.), Elsevier, Amsterdam..

Neuendorffer, A.C., 1996: Ozone Monitoring with TIROS-N operational vertical sounders. J. Geophys. Res., 101,18807-18828.

Paltridge, G.W. & I.J. Barton, 1978: Erythemal ultraviolet radiation distribution over Australia- Calculations, detailed results and input data.. Aust. Div. of Atmos. Phys., Commonw. Sci. and Ind. Res. Organ., Melbourne, Victoria. Tech. Pap., No 33, 48pp.

Stamnes, K., S. C. Tsay, W. J. Wiscome, and K. Jayaweera, 1988: Numerically-stable algorithm for discrete-ordinate method radiative transfer in multiple scattering and emitting layered media, Appl. Opt., 27, 2502-2509.

Teillet, Philippe. M, 1990: Rayleigh optical depth comparison from various sources. Appl. Opt. 29, 1987-1900.

Woods, T.N., Prinz, D. K., Rottman, G. J., London, J., Crane, P. C., Cebula, R. P., Hilseranth, E., Brueckner, G. E., Andrews, M. D., White, O. R., VanHoosier, M. E., Floyd, L. E., Herring, L. C., Knapp, B. G., Pankratz, C.K. & Reiser, P. A., 1996: Validation of the UARS solar ultraviolet irradiances: Comparison with Atlas 1 and 2 measurements. J. Geophys. Res., 101, 9541-9569.

WHO, 2002: Global Solar UV Index, A practical Guide. Fact Sheet 271. http://www.who.int/mediacentre/factsheet/who271/en/index.html.

WMO, 1995: Panel Report of the WMO Meeting of Experts on UV-B measurements, Data Quality and Standardization of UV Indices. WMO/TD No.625.


For further information contact Dr. L. Lemus-Deschamps: L.Deschamps@bom.gov.au


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