WORLD METEOROLOGICAL ORGANIZATION

UNITED NATIONS ENVIRONMENT PROGRAMME

NORWAY

1. Network for UV measurements
In 1995 a new national network for measurement of UV radiation was put into operation. The network is partly funded by the State Pollution Control Authority (SFT) and partly by the Ministry of Health. The Norwegian Institute for Air Research (NILU) operates three stations (Oslo, Tromsø and Ny-Ålesund), and the National Radiation Protection Authority (NRPA) operates four stations in Southern Norway. The network is based on Biospherical Instruments GUV-511, but the instruments have been modified so that the PAR channel has been replaced by a channel at 313 nm. This modified model is called GUV-541. A radiative transfer model developed at NILU makes it possible to calculate erythemal dose rates and total column ozone.

2. ALOMAR ozone LIDAR
The Arctic Lidar Observatory for Middle Atmosphere Research (ALOMAR) is located at the island of Andøya in Northern Norway at 69°N and 16°E. The observatory consists of several lidar instruments for measurements of aerosols, temperature and winds. The Norwegian Space Centre in collaboration with the Norwegian Defence Research Establishment (NDRE) and NILU run a DIAL ozone LIDAR. The instrument has been in operation since December 1994. Other instruments are operated by institutions in Germany, France, UK, Canada and USA.

3. Dobson measurements
Three Dobson instruments are currently in operation: In Oslo (60°N, 10°E), Tromsø (70°N, 19°E) and Ny-Ålesund, Spitsbergen (79°N, 12°E). The instrument in Oslo has measured continuously since 1978, the one in Tromsø since 1984, and the one in Spitsbergen since 1984. For Tromsø there is also a time series from 1939 to 1971, and work is under way to recalibrate these data, so that the old and new time series can be compared directly. The instruments in Oslo and Spitsbergen are operated by the University of Oslo, and the one in Tromsø is operated by the University of Tromsø. The work is funded by SFT and is coordinated by NILU.

4. Brewer measurements
Norway has two Brewer spectrophotometers; one in Oslo (since February 1990) and one in Tromsø (since May 1994). The instruments have been funded by SFT. The instrument in Oslo is operated by the University of Oslo. and the one in Tromsø is operated by NILU and the University of Tromsø in cooperation. The work is funded by SFT and coordinated by NILU.

5. The NILUV instrument
NILU has recently developed a 5 channel filter based instrument for measurement of UV radiation. Several prototypes have been built, and eight NILUVs have been used in a field study in Torres del Paine National Park in Patagonia where the influence on UV radiation on the flora was studied. This work was carried out as a cooperation between NILU, the University of Tromsø and the University of Magellanes in Punta Arenas. Through a joint venture of NILU and local industry the NILUV will be commercialized. The instrument can be delivered with software for computation of dose rates and total column ozone.

6. UV measurements in Chile
NILU operates a network of three GUV-511 filter instruments in Chile. The three stations are Punta Arenas, Valdivia and Santiago. This work is supported by the Norwegian Ministry of the Environment. The ownership of the instruments has been transferred to the Chilean government. The data evaluation is done as a cooperation between Chilean and Norwegian scientists.

7. UV-Vis spectrometers in Spitsbergen
NILU operates two UV-Vis spectrometers in Ny-Ålesund, Spitsbergen. One is the commercially available SAOZ instrument (SAOZ = Système pour Analyse d' Observations Zénithales), and the other is assembled at NILU and baptized SYMOCS (System for MOnitoring of Compounds in the Stratosphere). Both instruments consist of a grating spectrograph and a 1024 diode array detector. The SYMOCS detector is cooled to - 40°C. The SAOZ was upgraded from 512 to 1024 diodes in January 1996. Both instruments measure total ozone and total NO₂, and the SYMOCS has been constructed in order to measure OCIO and BrO as well.

8. Ground based measurements at Harestua
The former solar observatory at Harestua, just north of Oslo at 570masl was put into operation as a ground based station during the Second European Stratospheric Arctic and Mid-latitude Experiment (SESAME). In order to understand how polar processes influence the ozone layer at middle latitudes it is necessary to carry out measurements in the transition region around 60°N. The Institute for Water and Air Research (IVL) in Gothenburg, Sweden, operates a Bruker FT- IR instrument in order to measure a number of compounds, such as HCI, HF, HNO₃, NO₂ and CIONO₂. The Belgian Institute for Space Aeronomy (BISA) operates a UV-Vis spectrometer for measurement of total columns of ozone, NO₂, OCIO and BrO. The station is owned by the University of Oslo, and NILU assists BISA and IVL in running the instruments.

9. Ozone soundings
Three Norwegian ozone sounding stations are now in operation; Gardermoen (60°N, 11°E), Ørland (64°N, 10°E) and Bjørnøya (Bear Island) (75°N, 19°E). All three stations have participated in the SESAME campaign, and they will also participate in the newly started OSDOC project. The stations belong to the Norwegian Meteorological Institute (DNMI), and NILU is responsible for the ozonesonde operation. Bjørnøya has been in operation since October 1988, Gardermoen since November 1990 and Ørland since January 1995. Bjørnøya has a regular programme of one sounding per week around the year, whereas the two other stations launch less often (1- 2 soundings per month). During campaigns all three stations launch up to 3 soundings per week.

10. Validation of GOME
The Global Ozone Monitoring Experiment (GOME) was launched on board the ERS-2 in April 1995. NILU has played a central role in the validation of the instrument. Firstly, NILU contributes with total ozone measurements from Norwegian stations and with total ozone from the GUV instruments in Norway and Chile. The advantage of the GUV is that it gives very frequent measurements, so that one can find satellite and GUV measurements that coincide in time. A NILUV instrument placed at ALOMAR has also participated in the validation of GOME.

11. Atmospheric chemistry modelling
Atmospheric chemistry modelling of the stratosphere is carried out in two different groups; at the University of Oslo (Geophysics Dept.) and at NILU. The group at the University works with a 2-D model for predictions of future changes of the ozone layer. Recently, a 3-D model has been implemented, but work is still going on to verify the model. The stratospheric group at NILU works mainly with a trajectory model, but a 2-D model will be implemented in 1996.

12. Radiative transfer modelling
A radiative transfer model based on Chandrasekhar's discrete ordinate method has been in use at NILU for several years. This model is used for the calculation of UV dose rates and for air mass factors for conversion of slant column abundances into vertical columns. One advantage of the discrete ordinate method is that all orders of multiple scattering are inherently included. Another advantages is that the model is independent of optical depth, so that optically thick atmospheres can also be treated. The model can consider mixed atmospheres containing Mie and Rayleigh scatterers as well as mixtures of absorbing gases.

13. Analysis of data
Various types of experimental data are analysed, especially UV-Vis data, ozonesonde data and meteorological data. The seasonal dependence of ozone air mass factors for stations at various latitudes has recently been calculated. Ozonesonde data acquired inside the polar vortex during the winters from 1988-89 to 1994-95 has been analysed with respect to ozone destruction. Meteorological data from ECMWF are analysed in order to follow the temperature trend in the stratosphere and in order to assess the geographical area covered with PSCs at various levels.

14. NADIR
Since 1991 NILU has built a data centre for European stratospheric ozone scientists. The data centre started out as the central data handling facility for the EASOE campaign that was held in the winter of 1991 -92. This was followed up during SESAME and will also be continued during 199698. The data centre stores experimental data acquired by various research groups, and the data are made available to all the other participants in the project. One important service provided by NADIR is the easy access to meteorological data from ECMWF. Such data are difficult to access for scientists who are not affiliated with national meteorological institutes. At NADIR such data are easily accessible, and a large number of programs are available for extraction and plotting of data.

15. SESAME, OSDOC and other EU projects
Norwegian stratospheric ozone scientists participate in several projects with funding from the European Commission within the Environment and Climate Programme. During 1994 and 1995 several Norwegian scientists participated in the SESAME campaign and related projects. From 1996-98 the OSDOC project will play a central role in the ozonesonde activities in Europe. Several hundred ozonesondes will be launched from many stations in Europe in order to assess the chemical depletion of ozone both in the Arctic and at middle latitudes. One important issue s how polar processes affect the ozone layer at middle latitudes.

16. Where to find more information?
Information about Norwegian stratospheric ozone research can be found at the following World Wide Web address:
http://www.nilu.no. If you have questions, don't hesitate to contact Geir Braathen at +47 63 89 81 80 or E-mail geir@nilu.no.