Ozone and UV Radiation Monitoring
Department of Physics
University of Oslo
NORWAY

The two figures below show the last observed UV index and cloud transmission measured with our GUV-511 instrument. The figures are normally updated every 30 minute throughout the day. The UV INDEX is a measure of how intense the solar UV radiation are. The CLOUD TRANSMISSION describes the effect of cloud cover on the UV radiation. 100% represents clear sky. Clouds will usually lower the UV index. For example a cloud transmission of 70% mean that the UV index is 70% of the clear sky value.

Select date (dd/mm/yy):

Uv Dose Rate

Select date (dd/m/yy):

Sky Transmission

The figure below shows the UV index day-by-day at noon for the present year. To compare, the UV index at the Canari Islands is around 11 in June and 3-4 in December. At 40 degrees latitude (Mediterranean) the UV index is around 9 in June.

MEASUREMENTS OF TOTAL OZONE

The amount of ozone is changing throughout the year, with the highest values in the spring ond the lowest values in the autumn In addition you can see from the figure below that the ozone can vary a great deal from one day to another. Daily variations of 20% is quite normal and during the spring the variations can be even larger. At The Department of Physics we have a continous observation serie from 1979. Analysing these observations we can see that from 1979 to 1997 the average reduction is 0.4% per year.

Our latest ozone measurement:

The figure below shows the daily amount of total ozone for this year measured with the GUV-511


Total ozone 1979-2006
(Dobson and Brewer measurements)

1979	1989	1999
1980	1990	2000
1981	1991	2001
1982	1992	2002
1983	1993	2003
1984	1994	2004
1985	1995	2005
1986	1996	2006
1987	1997
1988	1998

OUR INSTRUMENTS

The Brewer Instrument
The Brewer is designed to measure total ozone and the abundance of sulphur dioxide in the atmosphere. In addition the instrument measures direct and global (direct + diffuse) spectral irradiance in the wavelength range 290 - 372 nm. If direct sun is available total ozone is derived from direct sun measurements at 4 UV wavelengths. For cloudy sky conditions ozone may be derived from scattered UV radiation from the zenith direction. The present algorithm for derivation of ozone from zenith sky measurements is sensitive to clouds. Therefore we use a modified ds routine to redirect the 5 Brewer standard wavelengths through the UV-B irradiance port and use similar technique as with the GUV-511. This technique has shown to be little sensitive to clouds and therefore our Brewer now provide high quality ozone measurements the year around. The Brewer operates to a large extent automatically and is controlled by a PC. Our Brewer has been in operation since 1990.

Take a closer look at the Brewer Instrument :

The Dobson spectrophotometer.
The Dobson instrument was developed by G.M.B. Dobson in the 1920ies. It is designed to measure total ozone abundance in the atmosphere. The instrument is operated manually and the ozone abundance is deduced from direct sun measurements or when the sky is cloudy zenith sky measurements are used. The Dobson instrument is known to be a very stable instrument and today still constitutes the basis of the global ozone monitoring network.

The Instrument GUV-511
This is a 5 channel instrument designed to measure UV irradiances in 4 channels, with center wavelengths at 305 nm, 320 nm, 340 nm and 380 nm. Bandwidths are approximately 10 nm FWHM (Full Width at Half Maximum). The fifth channel is a PAR channel (Photosynthetically Active Radiation, 400-700 nm). The instrument is manufactured by Biospherical Instruments Inc, USA. The instrument are temperature stabilized at 40 degrees C. Time resolution 1 min. Using a technique developed by Dahlback (1996), we are able to derive from the raw data total ozone abundance, cloud cover information, complete spectra from 290 to 400 nm and biologically weighted UV doses for any action spectra in the UV. The irradiance measurements may also be used to derive spectral actinic fluxes to compute photodissociation rates for different photochemically processes (Beine et al, 1999).

Dahlback, A., Measurements of biologically effective UV doses, total ozone abundances, and cloud effects with multichannel, moderate bandwidth filter instruments (1996), Appl. Opt., Vol. 35., No.33, 6514-6521.

H.J, Beine, A. Dahlback and J.B. Ørbæk, Measurements of J(NO2) at Ny-Ålesund, Svalbard (1999), J.Geophys: Res. Vol. 104, No. D13, 16009-16020

Scientific Staff

Professor Arne Dahlback	(+47) 2285 5657	arne.dahlback[]fys.uio.no
Tove M. Svendby	(+47) 2285 5641	t.m.svendby[]fys.uio.no
Lars Opedal	(+47) 2285 5662	lars.opedal[]fys.uio.no

Oppdatert 20.02.01 av Lars Opedal