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Ozone and UV Program


Research and Monitoring







The three main objectives of the Ozone & UV Program are:

  • Ozone and UV radiation monitoring with the highest precision and long term stability available with the current technology and scientific knowledge.

  • Research the evolution of ozone and UV in the subtropical region.

  • Investigate instrumental and methodological techniques improvement for measuring ozone.

To meet these objectives the Program is organized into four interconnected areas: instrumentation, calibration, modeling and data dissemination. The long term maintenance of the instrumentation is supported by strict QA/QC protocols which require both calibration laboratory and theoretical modeling. Finally web oriented databases are developed and maintained for data real-time dissemination.

Research and Monitoring

Total ozone and spectral Ultraviolet radiation started at Izaña Observatory (IZO) in May 1991 with the installation of the Brewer spectrometer #033. Ozone profile measurements were added in September 1992 with two-daily (sunrise and sunset) vertical ozone profiles with the Umkehr technique.  Since November 1992 a continuous ozonesonde program is being performed on a weekly basis. In July 1997 the double Brewer#157 was installed at Izaña and run in parallel for six months with Brewer#033. In 1997 a Bentham spectrophotometer was setup at the observatory expanding the wavelength range of the UV observation from 290-325 of the Brewer to 280-400 nm. In 2003 the double Brewer #183 was installed as travelling reference of the Regional Brewer Calibration Center for Europe (RBCC-E). In 2005 a third double Brewer, the #185 was installed to complete the RBCC-E’ reference triad. 
Total Ozone
Total ozone is now monitored at both IZO and SCO. The total Ozone program at IZO is part of the

Network for the Detection of Atmospheric Composition Change (NDACC) program. A long-term total ozone series is shown in the following figure:


A part of the NDACC program, the main activity concerning total ozone is the maintenance of the Regional Brewer Calibration Center for Europe (RBCC-E).

The Regional Brewer Calibration Center- Europe (RBCC-E)

The Regional Brewer Calibration Center for Europe (RBCC-E) was established in 2003. The RBCC-E maintains a triad of reference instruments necessary to transfer the calibration scale to the European Brewer network through annual calibrations campaigns performed in selected European facilities.

Calibrations of Brewer spectrophotometers for total ozone observations can be performed either by intercomparison against a reference instrument (the most frequent method) or by absolute calibration using Langley method (feasible only at specific high mountain sites with pristine skies). At present, there are about 50 brewer spectroradiometers in Europe; most of them are calibrated individually on a rather low level of coordination. Although the IZO triad is regularly calibrated by the Langley method, this absolute calibration is not used for definition of a new calibration scale. The World triad reference, maintained by the Meteorological Service of Canada (MSC), is respected as the official reference of the GAW Brewer international scale. The RBBC-E instruments have the purpose to spread the above mentioned reference to Brewers operating in Europe and recently in Northern Africa. The IZO and MSC triads are linked by the Canadian travelling reference Brewer 017, which is brought to RBCC-E on a yearly basis. The establishment of an IZO triad allows the implementation of a self -sufficient European Brewer calibration system that respects the world scale but works as an independent GAW infrastructure.

Important objectives such as validation of satellite instruments operating under European space missions are possible after a reliable calibration system such as the RBCC-E. The function of RBCC-E also allows development and testing of new measurement techniques for the ground Brewer network like zenith, UV or aerosol optical depth measurements.
The most remarkable projects of the RBCC-E are the following:
1.    ESA  - Cal Val Project: The main objective is to improve the quality of ground based instrument for satellite validation. To achieve this end, three types of the intercomparisons of instruments will be supported by this project:
  • RBCC-E Calibrations: Selected Brewers from Europe and North-Africa will be operated in parallel to the European reference instruments (triad and/or traveling reference). Campaigns are planned in Spain, Switzerland and Northern Africa.
  • Langley Calibrations: The European standard Dobson will be operated at Izana together the European double Brewer reference triad.  The performance and calibration of the Dobson will be evaluated and assessed.
  • Nordic Calibrations: The Brewer from the Finnish Meteorological Institute (FMI), operational since 1988, will be operated for 4-6 weeks in parallel to the European double Brewer reference triad at Izana (during the Northern Polar Winter). The premise is to perform an absolute calibration of the Finnish Brewer and transfer this information to other Nordic instruments.
2.    AECI-WMO GAW-Sahara Project: The International Agency for Cooperation to the Development of Spain, through GAW-WMO, has financed a double Brewer to be installed in the Global GAW Tamanrasset station (Algeria) in early 2010. In 2009 the RBCC-E will provide training to the Tamanrasset staff, and calibration services to the double Brewer. The final installation of the Brewer will be also performed by the RBCC-E. The Tamanrasset station operates on a long term basis a Dobson spectrophotometer. So, Tamanrasset will become one of the few places in the world for studying Brewer-Dobson differences (highly recommended by the SAG-Ozone) and a unique site for satellite validation over a desert environment.

Other past RBCC-E missions have been the following:

-    Participation of the RBCC-E traveling reference Brewer in the two SAUNA campaigns (March and April 2006 and 2007, respectively) financed by NASA.
-    Brewer team training, repairing, calibration and installation of the Brewer#155 at the Artigas Antarctic Base (Antarctic Institute from Uruguay).
-    Brewer team training, repairing and calibration (2005 and 2007) of the double Brewer#165 and single Brewe #051 located at Casablanca (Direction de la Météorologie Nationale; Morocco).

Detailed and up-to-date information about the RBCC-E calibration campaigns can be found on RBCC-E web site.

A fully accessible web-based database has been implemented within the RBCC-E. This data base, named Iberonesia provides, not only near-real time total column ozone and UV data from Brewers from Spain, Moroccco and Portugal, but also the tracking of most instrument parameters and calibrations. The network is able to issue warnings to every member Centre reporting abnormal parameter values after internal data checks and comparisons. Nearby Brewers, historical ozone series and daily values provided by OMI and other satellite-sensors are employed for quality control.

Ozone vertical profiles Program
The program of in-situ vertical ozone profiles at Izaña Observatory was initiated in November 1992 (ECC electrochemical sondes) with regular flights with a frequency of one per week from Santa Cruz de Tenerife station (36 m.a.s.l.), distant 28 km from Izaña Observatory. This program provides ozone profiles from the ground to the burst level (generally between 30 and 35 km) with a resolution of a few 100 meters. The frequency of ozone soundings in this station is significantly expanded during intensive campaigns. The main features of the ozone sonde system are the following:
  • Sensor: ECC-A6

  • Radiosonde: RS-92

  • Interface: RSA 11

  • Balloon: TOTEX  TA 1200

  • Receiver: Digicora Marwin MW-11

  • Wind system: GPS

  • Data acquisition system: Väisäla Met graph with NASACONV.

The ozonesondes are checked before launching with a Ground Test with Ozonizer/Test Unit TSC-1. A constant mixing ratio above burst level is assumed for the determination of the residual ozone if an altitude equivalent to 17 hPa has been reached. The integrated ozone column (starting at 2400 m a.s.l.), for those ozone sondes that reach a burst level of at least 17 hPa, is ratioed with the same column amount measured with the Brewer#157 located at Izaña Observatory (WMO ozone station #300). Simultaneously integrated total column from ground is ratioed against the total ozone measured by the Brewe#033 installed at Santa Cruz de Tenerife (52 m a.s.l.). Most of the Brewer/ECC coefficients fall in the 0.95-1.05 range. This coefficient is only used as a quality control parameter but it is not applied to the tropospheric ozone, as it is suggested Jülich KFA ozonesonde calibration center. Pump efficiency correction is applied and the box temperature is measured with the thermistor in the pump hole, as recommended by the quality control team of THESEO.
This program is part of the NDACC network. The NDACC quality control and quality assurance requirements are met at Tenerife ozonesonde station. Data is routinely archived into the NDACC and NILU databases. Tenerife station has participated in annual THESEO campaigns and in field experiments carried out in the framework of different EC projects (BOA, CRISTA and REVUE).

Ozone sounding, Santa Cruz de Tenerife
A new ozonesonde observation programme has finally been implemented in April 2008 at the Global GAW Ushuaia station. This program is a joint initiative of AEMET (Through the Izaña Atmospheric Research Center), the INTA (Spain), the Argentinean Meteorological Service and the Government of Tierra del Fuego (Argentina). See Cooperation Program with the Ushuaia Global GAW station.

Ultraviolet Radiation

Spectral UV radiation is routinely measured by the Brewer spectrophotometer. UV scans within 290-325 nm range (1991-1998) and 290-365 nm range (1998-now) are taken every half an hour.  Due the short wavelength range of the Brewer, the UV radiation is also measured since 1999 with a Bentham DM 150 spectrometer (250-600 nm). The Bentham spectrometer is updated now to meet NDACC requirements and is the main instrument to monitor spectral UV radiation. Recently, a UV-VIS CCD spectrometer has been set up at IZO for measuring global and direct spectral radiation at the 300-900 nm range.
The NILU Antarctic Network

In the framework of several projects funded by previous calls of the National R+D Plan of the Ministry of Education of Science, three UV-VIS spectrometers (EVA) designed and developed at INTA to measure column NO2 and O3 were installed at the permanent Argentinean bases of Belgrano (77º 52' S 34º37' W), Marambio (64º 14' S 56º37' W) and Ushuaia (54º 48' S 68º19' W), respectively, in 1994. The selected stations are scientifically of interest for Polar atmosphere studies since they cover areas in the stratosphere dynamically and chemically differentiated. The southernmost, which is Belgrano, is mostly located inside the vortex, Marambio is on the edge, and Ushuaia right outside the vortex. Three multi-channel narrow-band radiometers (NILU-UV6) were co-located by the Izaña Atmospheric Research Center in the UV-VIS Antarctic stations in 1999, thanks to the scientific collaboration agreements signed by AEMET, INTA, DNA/IAA (Argentina) and the CADIC (Argentina). A fourth NILU-UV-6 is operated at the GAW Izaña Observatory. The NILU-UV6 instruments measure global radiation at five UV channels and PAR. A radiative transfer model is used to calculate the total ozone content, cloud transmittance and the biologically effective UV doses. Both complementary instruments are part of the Spanish Antarctic network that is now coordinated in the framework of some joint INTA-AEMET’s projects (“MAR” REN2000-0245-C02-01; EGEO CGL2004-05419-C02-02ANT), financed both by the R+D National Program. The Finnish Meteorological Institute (FMI) is in charge of the NILU radiometers’ quality assurance system performing intercomparisons twice a year with a traveling reference NILU. The main objective of this network is to provide both long term and near real-time observations of column O3 and UV radiation in order to characterize the polar vortex.

A new web-based database has been designed to manage all the information from the NILU Antarctic Network. This new tool allows the user to see measurements taken by the NILU-UV radiometers in an organized manner, to process calibrations automatically, and to obtain in real time the total ozone content and the UV radiation following the Quality Control application. This system allows us to monitor the evolution of the ozone layer and UV radiation in the Antarctic region, which is of particular interest during the period of formation of the Polar Vortex.
The first contribution of Antarctic Network of NILU-UV Radiometers to the Antarctic Ozone Bulletin (November, 2006) can be found here.


The infrastructures for the ozone and UV program consists basically on the terrace of the observation tower at Izana Observatory (IZO), the terrace of the Observatory at Santa Cruz (SCO), and the laboratory and ozonesonde launching platform at the Meteorological Center of Santa Cruz de Tenerife. This facility will be moved to the Botanic garden in Puerto de la Cruz (northern part of the Tenerife Island) within 2009.


Brewer Spectroradiometers:

Spectroradiometer: Double monochromator 290-365 nm range, focal 160 mm, FHWM=0.6 nm.
Automatic and outdoors operation.
Total ozone content
Total SO2 content
UV global spectral Radiation
Ozone profile by Umkehr  method
Aerosol Optical depth

Bentham Spectroradiometer

Bentham DM 150 Double  Spectroradiometer:

  • 250-600 nm range, FWHM 0.6 nm.
  • Global and direct input optics.
  • Temperature Stabilized.




  • Five UV channels centered at 305, 312, 320, 340 and 380 nm (10nm FWHM)
  • PAR (Photosynthetic Active Radiation) 400-700nm
  • Stabilized temperature: 40 ºC
  • Products:
Total ozone content
Radiation UV-A and UV-B
Clouds transmission factor (CLT)
Biologically effective UV doses (CIE)

CCD- Spectrometer

Global and Direct input optics
Temperature stabilized, automatic operation
Total number of pixels: 3648
Wavelength range: 284-607 nm
Slit size : 50 µm
FWHM: 1nm
A/D resolution: 16 bit



This program has been involved in the following research projects.
European projects:
  1. Budget of Ozone over the North Atlantic (BOA) (Environmental Program EV5V-CT93-0315).
  2. Investigation of the Oxidizing Capacity of the Atmosphere by Measurement of All Relevant Parameters Over Areas of Different Meteorological Conditions and Different Pollutional Impact (Environmental Program EV5V-CT-93-0321).
  3. Stratospheric Climatology Using Ultraviolet-Visible Spectroscopy (SCUVS); 1994-1996.
  4. Reconstruction of Vertical Ozone Distribution from Umkehr Estimates (REVUE), (Environmental Program ENV4-CT95-0161).
  5. Scientific UV DAta Management; EU (Environmental Program ENV4-CT95-0177).
  6. Standardization of Ultraviolet Spectroradiometry in Preparation of an European Network; EU (Environmental Program, ENV4-CT95-0056).
  7. TRansport of Chemical species Across the Subtropical tropopause (TRACAS), (Environmental Program ENV4-CT97-0546).
  8. Small Scale Structure Early Warning and Monitoring in Atmospheric Ozone and Related Exposure to UV-B Radiation (STREAMER), (Environmental Program ENV4-CT98-0756).
  9. SCOUT- O3 (Stratosphere - Climate Links With Emphasis On The UTLS)
National R+D Plan:
  1. Medida y Modelización de la Distribución Espacio-Temporal de la Irradiancia Solar Ultravioleta en España. Programa Nacional del Clima CLI97-0345-05.
  2. Red Antártica para la vigilancia y Caracterización de la Radiación UltraVioleta (RACRUV). Programa Nacional de Investigación Antártica ANT98-0179.
  3. Control de Calidad de la Red Antártica para la vigilancia y Caracterización de la Radiación UltraVioleta (CRACRUV). Programa Nacional de Investigación Antártica REN2000-0245-C02-02.
  4. Determinación y predicción de la radiación ultravioleta solar en España: influencia de la columna de ozono, partículas aerosoles y nubosidad. Programa Nacional del Clima REN2000-0903-C08-02 CLI.
  5. Determinación y predicción de la radiación ultravioleta solar en España: Influencia de la columna de ozono, partículas aerosoles y nubosidad (DEPRUVISE) (CLI2000-0903-C08) (2001-2004).
  6. ROBOT (Red de Observación Brewer para la Medida Automática de Espesor Óptico de Aerosoles); Plan Nacional I+D (CGL2004-05984-C07-06).
  7. MANA (Red Antártica para la medida de Aerosoles); Plan Nacional I+D (CGL2004-05419-C02-02/ANT)
  8. TROMPETA (“TROpical Monitoring Phase in the Atmosphere”); Plan Nacional I+D (CGL2004-03669/CLI)
International intercomparison campaigns (since 2005)
  1. An intercomparison campaign of seven UV spectroradiometers of different types took place at Izaña Observatory in June 2005. The campaign was focused primarily on spectral measurements of direct solar irradiance. Among the objectives was to improve the quality of direct solar irradiance spectral measurements, through instrumental modifications and standardization of calibration techniques, as well as to assess the significance of the differences in the field of view of the spectroradiometers with respect to aerosols and to solar zenith angle.
  2. In September 2005 and September 2007 were held the first and the second, respectively, Brewer intercomparison campaigns at El Arenosillo station (INTA). The scientific coordination and organization corresponded to the GAW Regional Brewer Calibration Center for Europe (RBCC-E). During the second Brewer intercomparison in 2007 a Dobson intercomparison campaign was organized by the Regional Dobson Calibration Centre-Europe (WMO-RDCC-RA-VI) Meteorological Observatory Hohenpeissenberg (Germany).  During the first days both calibration campaigns performed in parallel, while the last days were used for a Dobson/Brewer comparison. In the two Brewer intercomparisons two Brewers from Morocco were fitted and calibrated.
  3. The third RBCC-E intercomparison was held at the Arosa Observatory (MeteoSwiss).
  4. The RBCC-E has hosted the first intercomparisons of the World and European Brewer and Dobson reference instruments at Izaña on September 7-27, 2008.


Coordinator: Alberto Redondas

RBCC-E: Juanjo Rodríguez (AEMET – graduate student)

NILU Antarctic network: Fernando Almansa (AEMET- graduate student) 

Ozonesonde program: Sergio Afonso (AEMET)

Laboratory: Carmen Guirado (UVA-AEMET PhD contract)


UVI Forecasting: Virgilio Carreño (AEMET)

QA/QC: Rosa García (UVA-AEMET PhD contract)


Schneider, M., A. Redondas, F. Hase, C. Guirado, T. Blumenstock, and E. Cuevas, “Comparison of ground-based Brewer and FTIR total column O3 monitoring techniques”, Atmospheric Chemistry & Physics, Vol. 8, Sep. 2008.

Schneider, M., F. Hase, T. Blumenstock, A. Redondas, and E. Cuevas, “Quality assessment of O3 profiles measured by a state-of-the-art ground-based FTIR observing system,” Atmospheric Chemistry & Physics,  vol. 8, Sep. 2008.

Fioletov, V.E., G. Labow, R. Evans, E.W. Hare, U. Köhler, C.T. McElroy, K. Miyagawa, A. Redondas, V. Savastiouk, A.M. Shalamyansky, J. Staehelin, K. Vanicek, and M. Weber, “Performance of the ground-based total ozone network assessed using satellite data,” Journal of Geophysical Research (Atmospheres),  vol. 113, Jul. 2008.

Redondas, A., C. Torres, O. Meinander, K. Lakkala, R. García, E. Cuevas, H. Ochoa, G. Deferrari, and S. Díaz, “Antarctic network of lamp-calibrated multichannel radiometers for continuous ozone and uv radiation data,” Atmospheric Chemistry & Physics Discussions,  vol. 8, Feb. 2008.

Schoeberl, M.R., J.R. Ziemke, B. Bojkov, N. Livesey, B. Duncan, S. Strahan, L. Froidevaux, S. Kulawik, P.K. Bhartia, S. Chandra, P.F. Levelt, J.C. Witte, A.M. Thompson, E. Cuevas, A. Redondas, D.W. Tarasick, J. Davies, G. Bödeker, G. Hansen, B.J. Johnson, S.J. Oltmans, H. Vömel, M. Allaart, H. Kelder, M. Newchurch, S. Godin-Beekmann, G. Ancellet, H. Claude, S.B. Andersen, E. Kyrö, M. Parrondos, M. Yela, G. Zablocki, D. Moore, H. Dier, P. von der Gathen, P. Viatte, R. Stubi, B. Calpini, P. Skrivankova, V. Dorokhov, H. De Backer, F.J. Schmidlin, G. Coetzee, M. Fujiwara, V. Thouret, F. Posny, G. Morris, J. Merrill, C.P. Leong, G. Koenig-Langlo, and E. Joseph, “A trajectory-based estimate of the tropospheric ozone column using the residual method,” Journal of Geophysical Research (Atmospheres),  vol. 112, Dec. 2007.

Oltmans, S., A. Lefohn, I. Galbally, E. Scheel, G. Bödeker, E. Brunke, H. Claude, D. Tarasick, P. Simmonds, K. Anlauf, F. Schmidlin, K. Akagi, and A. Redondas, “Long-term Changes in Tropospheric Ozone,” AGU Spring Meeting Abstracts,  vol. 41, May. 2006.

Lakkala, K., A. Redondas, O. Meinander, C. Torres, T. Koskela, E. Cuevas, P. Taalas, A. Dahlback, G. Deferrari, K. Edvardsen, and H. Ochoa, “Quality assurance of the solar UV network in the Antarctic,” Journal of Geophysical Research (Atmospheres),  vol. 110, Ago. 2005.

Schneider, M., T. Blumenstock, F. Hase, M. Höpfner, E. Cuevas, A. Redondas, and J.M. Sancho, “Ozone profiles and total column amounts derived at Izana, Tenerife Island, from FTIR solar absorption spectra, and its validation by an intercomparison to ECC-sonde and Brewer spectrometer measurements,” Journal of Quantitative Spectroscopy and Radiative Transfer,  vol. 91, Mar. 2005.

Martínez-Lozano, J.A., M.J. Marín, F. Tena, M.P. Utrillas, L. Sánchez-Muniosguren, C. González-Frías, E. Cuevas, A. Redondas, J. Lorente, X. Cabo, V. Cachorro, R. Vergaz, A. Frutos, J.P. Díaz, F.J. Expósito, B. Morena, and J.M. Vilaplana, “UV Index Experimental Values During the Years 2000 and 2001 from the Spanish Broadband UV-B Radiometric Network” Photochemistry and Photobiology,  vol. 76, 2002.

Cuevas, E., M. Gil, J. Rodríguez, M. Navarro, and P. Hoinka, Sea-land total ozone differences from TOMS: The GHOST effect, J. Geophys. Res., Vol. 106, D21, p.p. 27745-27755, 2001.

de Backer, H., P. Koepke, A. Bais, X. de Cabo, T. Frei, D. Gillotay, C. Haite, A. Heikkil, A. Kazantzidis, T. Koskela, E. Kyrö, B. Lapeta, J. Lorente, K. Masson, B. Mayer, H. Plets, A. Redondas, A. Renaud, G. Schauberger, A. Schmalwiesser, H. Schwander, and K. Vanicek, “Comparison of measured and modelled uv indices for the assessment of health risks,” Meteorological Applications,  vol. 8, Sep. 2001.

Bais, A.F., B.G. Gardiner, H. Slaper, M. Blumthaler, G. Bernhard, R. McKenzie, A.R. Webb, G. Seckmeyer, B. Kjeldstad, T. Koskela, P.J. Kirsch, J. Gröbner, J.B. Kerr, S. Kazadzis, K. Leszcznski, D. Wardle, W. Josefsson, C. Brogniez, D. Gillotay, H. Reinen, P. Weihs, T. Svenoe, P. Eriksen, F. Kuik, and A. Redondas, “SUSPEN intercomparison of ultraviolet spectroradiometers,” Journal of Geophysical Research, vol. 106, Jun. 2001.

Gröbner, J., R. Vergaz, V.E. Cachorro, D.V. Henriques, K. Lamb, A. Redondas, J.M. Vilaplana, and D. Rembges, “Intercomparison of aerosol optical depth measurements in the UVB using Brewer spectrophotometers and a Li-Cor spectrophotometer,” Geophysical Research Letters,  vol. 28, May. 2001

Schulz, A., Rex, M., Harris, N. R. P., Braathen, G. O., Reimer, E., Alfier, R., Kilbane-Dawe, I., Eckermann, S., Allaart, M., Alpers, M., Bojkov, B., Cisneros, J., Claude, H., Cuevas, E., Davies, J., De Backer, H., Dier, H., Dorokhov, V., Fast, H., Godin, S., Johnson, B., Kois, B., Kondo, Y., Kosmidis, E., Kyrö, E., Litynska, Z., Mikkelsen, I. S., Molyneux, M. J., Murphy, G., Nagai, T., Nakane, H., O'Connor, F., Parrondo, C., Schmidlin, F. J., Skrivankova, P., Varotsos, C., Vialle, C., Viatte, P., Yushkov, V., Zerefos, C., von der Gathen, P., Arctic ozone loss in threshold conditions: Match observations in 1997/1998 and 1998/1999, J. Geophys. Res., 106, D7, 7495-7503, 2001.

Díaz, J.P., F.J. Expósito, C.J. Torres, V. Carreño, and A. Redondas, “Simulation of mineral dust effects on UV radiation levels,” Journal of Geophysical Research,  vol. 105, 2000.

Armerding, W., F.J. Comes, H.J. Crawack, O. Forberich, G. Gold, C. Ruger, M. Spickermann, J. Walter, E. Cuevas, A. Redondas, R. Schmitt, and P. Matuska, “Testing the daytime oxidizing capacity of the troposphere: 1994 OH field campaign at the Izaña observatory, Tenerife,” Journal of Geophysical Research,  vol. 102, May. 1997.