Ground based FTIR absorption measurements have been performed to study the zenith column densities of HF, N2O, CFC-12, and CFC-22. The spectra were recorded in the Arctic (Ny-¿lesund, Spitsbergen, 79¿N, 12¿E) during winter 1992/93 and spring/summer 1993. During the polar night the moon served as light source. The analysis of the spectra has been performed in the way to study vertical motions in the atmosphere. Compared to the summer observations a subsidence of -1.4 km at 12 km altitude and -4.9 km at about 15 km has been calculated for December 1992. For February 1993 the data yield a subsidence of -2.5 km at 12 km altitude and -6.3 km at about 15 km altitude. ¿ American Geophysical Union 1994