DOAS moonlight observation of atmospheric NO3 in the Arctic winter

The diurnal variation of the vertical column density (VCD) of NO3 was measu red during 16 nights in the winter 1993/94 (mid January - early March) at K iruna (68 degreesN, 21 degreesE) using the moon as light source. The lunar zenith angle (LZA) dependence of the NO3 absorption indicates that the majo rity (greater than or equal to 75%) of the atmospheric column was located i n the stratosphere. After a rapid increase within the first two hours after sunset the measured NO3 VCDs only slowly increase during the rest of the n ight. The NO3 VCDs (less than or equal to3.2.10(13) molec/cm(2)) are signif icantly larger compared to previous NO3, measurements in the Arctic. These differences can be most probably attributed to different atmospheric temper atures and differences in the correction of the H2O absorption structure in the NO3 analysis.