Recalibration of the hohenpeissenberg dobson spectrophotometer 104 presuming ?effective absorption coefficients?

Abstract

The well calibrated Brewer spectrophotometer 17 (Sci-Tec Instruments Inc., Canada) stayed at the Meteorological Observatory Hohenpeissenberg (MOHP) from August 27 until September 1, 1984, in order to check and recalibrate Brewer 10, which had some stability problems. Brewer 17 was initially calibrated in July 1983, the validity of this calibration was repeatedly verified before and after the stay at the MOHP (Kerr et al., 1985; Kerr, 1984). The instrument proved itself to be very stable and appropriate as travellings standard instrument. As Dobson 104 didn't seem to be well calibrated at that time, the occasion was taken to perform also a Dobson recalibration. The methods normally used were not satisfactory, but a different method, presuming ‘Effective Absorption Coefficients’ (EAC), presented by Kerr et al. at the Quadrennial Ozone Symposium 1984 in Greece, yielded encouraging results. Before recalibration Dobson 104 showed a difference of 2–3% in comparison to Brewer 10-, Brewer 17- and TOMS- (on satellite Nimbus 7) measurements, whereas the agreement with the Brewers after ‘EAC-calibration’ was good (ΔX rel < 1%). The different Dobson calibration methods are compared and the results of the Dobson 104 and Brewer 10 recalibrations are presented.