IMPROVING THE CONAE SOLAR UV INDEX FOR ARGENTINA

IMPROVING THE CONAE SOLAR UV INDEX FOR ARGENTINA Salum G. M. (1,), Piacentini R. D. (1,3), Cede A. (), Luccini E. (5), Marraco H. (), Machado M.E. () (1) Instituto de Física Rosario (CONICET Universidad Nacional de Rosario), Rosario, Argentina, () Facultad de Ingeniería/Universidad Nacional de Entre Ríos, Oro Verde, Entre Ríos, Argentina, (3) Facultad de Ciencias Exactas, Ingeniería y Agrimensura/Universidad Nacional de Rosario, Rosario, Argentina, () Science Systems & Applications Inc. NASA/Goddard Space Flight Center, Greenbelt, USA, (5) Departamento de Ciencias de la Atmósfera y los Océanos/FCEN/UBA, Buenos Aires, Argentina, () Comisión Nacional de Actividades Espaciales (CONAE), Buenos Aires, Argentina machado@conae.gov.ar

The Argentina National Commission on Space Activities (CONAE) has been forecasting the for solar risk prevention from November 199 up to the present. It is based on a parametric atmospheric radiative transfer calculation, including mainly the ozone attenuation from TOMS/NASA data and the altitude (pressure) and coordinates of the selected site. Daily predictions, for various locations of Argentina as well as for other countries are published via the web at www.conae.gov.ar. We present in this work the improved version of the CONAE UV Index using the TUV program developed by Madronich (www.acd.ucar.edu), with the inclusion of effective aerosol data estimated for each site. The forecast is also extended from one to several days in advance and a correction factor for cloudy sky is included.

0 1 1 1 1 CONAE YES biometer - Typical clear sky day data TUV Model (mean O3, "effective" aerosol) 199 La Quiaca: 199-199 1997 199 0 0 30 0 00 70 0 90 0 Consecutive day (1 = 1 Jan 199) Figure 1. at La Quiaca (.11ϒS, 5.57ϒW, 359 m asl), Argentina. The references values are measured with a YES biometer during clear sky days for the period 199 199. CONAE and improved one developed in the present work is obtained employing the TUV model with mean ozone from TOMS/EP NASA data base, mean effective aerosol of 0.1 at 30 nm, single scattering albedo of 0.99 and soil reflectivity of 0.0. The rest of the parameters are as given by default in the TUV algorithm.

0 1 1 1 1 5 3 1 La Quiaca: 199-199 TUV Model (mean ozone) TUV Model (ozone daily TOMS/NASA data) 199 1997 199 YES biometer vs TUV model (mean O3, "effective" aerosol) YES biometer vs CONAE 0.1 +/- 0.7 0-1 0.30 +/- 1.3 - -3 0 0 30 0 00 70 0 90 0 Consecutive day (1 = 1 Jan 199) Figure. Top. forecast for La Quiaca, Argentina, made with TUV model which considers mean ozone values and the rest of the parameters as describes in figure 1, compared with respect to the same type of forecast but considering daily ozone TOMS/EP NASA data. Bottom. with respect to YES biometer measurements, of the results obtained with the TUV program (see figure 1) and with the standard CONAE.

1 1 1 1999 Rosario: 1999-001 CONAE YES biometer - Typical clear sky day data TUV Model (mean O3, "effective" aerosol) 000 001 0 0 30 0 00 70 0 90 0 Consecutive day (1 = 1 Jan 1999) Figure 3. Same as figure 1, but for Rosario city (3.9 ϒS, 0. ϒW, 5 m asl), Argentina, during the period 1999 001 but with effective aerosol as in reference [1] and single scattering albedo of 0.93.

1 1 1 1999 Rosario: 1999-001 TUV Model (mean ozone) TUV Model (ozone daily TOMS/NASA data) 000 001 7 YES biometer vs TUV model (mean O3, "effective" aerosol) YES biometer vs CONAE 5 1.7 +/- 1.1 3 1 0-1 - -0.1 +/- 0.7-3 0 0 30 0 00 70 0 90 0 Consecutive day (1 = 1 Jan 1999) Figure. Same as figure, but for Rosario city, Argentina.

1 1 Buenos Aires: 1997-1999 CONAE SOLAR LIGHT biometer - Typical clear sky day data TUV Model (mean O3, "effective" aerosol) 1 1997 199 1999 0 0 30 0 00 70 0 90 Consecutive day (1 = 1 Jan 1997) Figure 5. Same as figure 1, but for Buenos Aires city (3.1ϒS, 5.1ϒW, 5 m asl), Argentina, during the period 1997 1999 but with mean effective aerosol of 0.55 at 30 nm and single scattering albedo of 0.93.

1 1 1 Buenos Aires: 1997-1999 TUV Model (mean ozone) TUV Model (ozone daily TOMS/NASA data) 1997 199 1999 3 1 0-1 - -3 SOLAR LIGHT biometer vs TUV model (mean O3, "effective" aerosol) SOLAR LIGHT biometer vs CONAE 0.7 +/- 0.9-0.39 +/- 0.5 0 0 30 0 00 70 0 90 Consecutive day (1 = 1 Jan 1997) Figure. Same as figure, but for Buenos Aires city, Argentina.

0 1 1 1 1 0 Base Marambio: 199-199 CONAE SOLAR LIGHT biometer - Typical clear sky day data TUV Model (mean O3, "effective" aerosol) TUV Model + Gauss function 199 1997 199 0 0 30 0 00 70 0 90 0 Consecutive day (1 = 1 Jan 199) Figure 7. Same as figure 1, but for Argentina Antarctic Marambio Base (.3ϒS, 5.7ϒW, 300 m asl), during the period 199 199 but with effective aerosol as in reference [1] and single scattering albedo of 0.93. Note: A Gauss function has been added to the mean UV index forecast in order to take into account the possible passage of the ozone hole over the geographical place. It is determined adjusting measured data.

1 Base Marambio: 199-199 SOLAR LIGHT biometer vs TUV model (mean O3, "effective" aerosol) SOLAR LIGHT biometer vs CONAE 199 1997 199 0 3 1 0-1 YES biometer vs TUV model (mean O3, "effective" aerosol) YES biometer vs CONAE 0.3 +/- 0.7 0.13 +/- 0.5 0 0 30 0 00 70 0 90 0 Consecutive day (1 = 1 Jan 199) Figure. Same as figure, but for Argentina Antarctic Marambio Base. Note: The UV index has been analyzed in the first semester period outside the ozone hole one.

CLOUD CORRECTION FACTOR We also propose to incorporate a cloud coverage correction factor, in order to determine the attenuation originated by cloudiness (measured in octas). The corresponding factor is the following [1]: Cloud coverage 0/ 1/ / 3/ / 5/ / 7/ /, near sea level 0.99 0.99 0.9 97% 0.9 0.91 0. 0.7 0.1, high altitude (La Quiaca) 0.9 0.9 0.9 0.9 0.97 0.9 0.90 0.7 0.5 CONCLUSIONS The main conclusions of the present work are: The detailed calculations of the UV index for Argentina, in general give a better agreement with the measured data (except eventually for La Quiaca for some periods) and a lower dispersion with respect to the previous calculations. Details about calibration and uncertainty analysis are given in reference []. The mean particular values for each location are: La Quiaca, Argentina YES biometer TUV 0.1 ± 0.7 YES biometer CONAE 0.30 ± 1.3 Buenos Aires, Argentina YES biometer TUV - 0.39 ± 0.5 YES biometer CONAE 0.7 ± 0.9 Rosario, Argentina YES biometer TUV - 0.1 ± 0.7 YES biometer CONAE 1.7 ± 1. Argentina Antarctic Marambio Base YES biometer TUV 0.13 ± 0.5 YES biometer CONAE 0.3 ± 0.7 Since the forecast made with mean ozone values is not very different from that obtained with daily values it to possible to make UV index predictions several days (and even weeks and months) in

advance. It must be pointed out that the annual mean ozone total column is rather constant in the present decade in the Sourthern Hemisphere [3]. For high Southern Hemisphere locations (like Marambio Antarctic Base) and during the ozone hole event, a gaussian function must be added to the normal forecast, in order to represent the maximum possible UV index to be attained in these geographical places. The present work complements the information provided by the Argentina National Weather Service through the ISUV (UV Solar Index) for clear and cloudy sky conditions [,5]. We improved the CONAE UV index for Argentina. This index is of importance in order to give indications of solar risk to persons exposed to intense Sun [1,,7]. ACKNOWLEDGEMENTS The authors like to thank the following institutions: ANPCYT and Fundación Antorchas, Argentina, for there support to the present work. REFERENCES [1] Cede A. Erythemal UV in Argentina: Measurements, climatological interpretation and comparison with satellite-derived data. Doctoral thesis, University of Innsbruck, Austria, 001. [] Cede A, Luccini E, Piacentini R D, Nuñez L y Blumthaler M, Calibration and uncertainty estimation of erythemal radiometers in the Argentina Ultraviolet Network. Applied Optics, 1, 31, 00. [3] WMO Scientific assessment of ozone depletion: 00. WMO Report, 003. [] Cede A, Luccini E, Nuñez L, Piacentini R D y Blumthaler M, Monitoring of erythemal irradiance in the Argentina Ultraviolet Network. Journal Geophysical Research 7, D13, 00 (DOI: 00/001JD00). [5] Argentina National Weather Service web page: www.meteofa.mil.ar. [] WHO (World Health Organization) Global solar UV index. A practical guide. Publication of WHO, 00. [7] Long, C. forecasting practices around the World, SPARC Newsletter 1, June 003.