Intercomparison of tropospheric OH radical measurements by multiple folded long-path laser absorption and laser induced fluorescence

An intercomparison of in-situ OH measurements by differential optical absorption spectroscopy (DOAS) and laser-induced fluorescence spectroscopy (LIF) was carried out in August 1994 in a clean rural environment in North-East Germany. A large data set of temporally overlapping OH measurements with well defined measurement errors was obtained and compared. Both instruments encountered the same air masses, except when the wind came from NNW and caused a perturbation of the DOAS measurements. Excluding that wind sector, the weighted regression analysis of 137 data pairs (70% of all available data pairs) yields a linear relationship between the BOAS and LIF measurements with a correlation coefficient r=0.90. The unity slope (1.01+/-0.04) and the non-significant intercept (0.28+/-0.15)x10(6) cm(-3) demonstrate that both OH instruments agreed excellently in their calibrations and accurately measured OH.