Scientific Sponsorship Statement Icelandic Meteorological Office (IMO) Reykjavik, Iceland 1. Dataset description Instrument: Dobson 50, Beck Site: IMO, Reykjavik, STN 51 (Lat. 64° 08’N, Lon. 21° 54’W) Altitude: 64 m Measurement: Total Ozone Column PI: Arni Sigurdsson 2. Instrument History Dobson 37 was first used to measure total ozone in Reykjavik in 1952 to 1955, but little is known about the reliability of this data set. Dobson 50 was installed in Reykjavik in July 1957 and the ozone measurements have been done on a regular basis since. The Dobson 50 was refurbished at Hohenpeissenberg in Germany in 2007. The mirrors and the electronics were renewed 3. Calibrations/Intercomparitions 1957 Oxford, UK – original calibration 1977 Boulder, Colorado, USA – new calibration and intercomparition with Dobson 83 1990 Arosa, Switzerland – intercomparition with Dobson 65 1995 Arosa, Switserland – Intercomparition with Dobson 65 2007 Hoherpeissenberg, Germay – Intercomparition with Dobson 64 2011 El Arenosillo, Spain – Intercomparition with Dobson 64 4. Data processing The orginal 1957 calibration proved to be inaccurate compared to later calibrations of the Dobson, therefore the calibration done in Boulder 1977 has been used from 1957 to 1977. In the process of recalculating the data set since 1957 one must rely on the standard lamp tests done during this period. The Na, Nc and Nd calibrations for the direct sun have been adjusted to the SL tests so that the differences Na - Nd and Nc - Nd in the SL-tests are almost constant during the whole period from 1957. The Dobson is calibrated to give reliable measurements on the direct sun. Because of the persistent cloudiness over Reykjavik there has been a need for good measurements on the zenith, derived from well calibrated direct sun measurements. The Nc calibration for the zenith blue measurements and the ZB polynomials were adjusted to fit the direct sun measurements done on the same day. The ZB Nc calibration is then in the same way used to adjust the N'c and the ZC polynomials to fit the direct sun measurements on cloudy days. The calibrations of Nc and N'c for the zenith measurements were adjusted, from period to period, in order to make the zenith measurements be in step with the direct sun measurements. During the darkest winter months from late November to January there was found to be a systematic difference between the zenith polynomial approximations (derived from observations in October and February) and the satellite ozone data. Satellite values being higher than the Dobson values. For the darkest period this difference has been corrected for so that the low sun Dobson values does not imitate the direct sun measurements in October and February, but the satellite ozone from late November to January. 5. Data usage permission The use of data has to follow the general rules of the WOUDC. Notifications of analysis work in progress are very welcome. The Icelandic Meteorological Office asks for a copy of any publication using data from the Reykjavik ozone station. 6. Contact Information Name: Arni Sigurdsson Address: Icelandic Meteorological Office Bustadavegur 5-7, 150 Reykjavik, Iceland Phone: +354 522 6000 Fax: +354 522 6002 Email: arnisig@vedur.is  7. Reference Articles Bjarnason, G.G.; Rögnvaldsson, O.E.; Sigfusson, T.I.;Jakobsson, T.; Thorkelsson, B., Analysis of Total Ozone Data from Reykjavik for the Period 1957-1991, Science Institute, University of Iceland, 1992. Bjarnason, G.G.; Rögnvaldsson, O.E.; Sigfusson, T.I.;Jakobsson, T.; Thorkelsson, B (1993), Total Ozone Variations at Reykjavik Since 1957, J. Geophys. Res., 98(D12), 23,059–23,077, doi:10.1029/93JD01912.