Performance of a differential optical absorption spectrometer for surface O 3 measurements in the finnish arctic

Abstract

A two-month comparison of ozone monitors was conducted by the Finnish Meteorological Institute (FMI) at the Sevettijärvi measurement station during winter 1993-94. The ozone concentrations measured by a commercial Differential Optical Absorption Spectrometry (DOAS) instrument and a conventional Dasibi 1008-AH monitor had a high and linear correlation. At low concentrations a small deviation from linearity was observed, which cannot be clearly accounted for by the observational data. Visibility is the most important factor affecting the performance of the DOAS. At low visibilities the correlation coefficient between the DOAS and monitor measurements was low. Therefore, approximately 3% of the ozone measurements in 1993 had to be rejected because of low visibility. The ozone concentrations measured at Sevettijärvi using the DOAS in 1993 were compared with those measured at two other measurement stations in Northeastern Lapland, Jäniskoski and Rajajooseppi. At these two stations, ozone is measured using conventional monitors. The distribution of hourly averaged concentrations is very similar at Sevettijärvi and Rajajooseppi. In particular, the correlation between the daily maxima at these stations is high. The concentrations are clearly highest at Jäniskoski. According to this study, the effect of the location of the measurement site on the measured ozone concentrations is larger than the effect of the measurement: method.