SEASONAL-VARIATIONS OF ATMOSPHERIC TRACE GASES IN THE HIGH ARCTIC AT 79-DEGREES-N

Since March 1992 the total column abundances of several tropospheric a nd stratospheric trace gases have been monitored year-round from the N etwork for Detection of Stratospheric Change station in Ny Alesund, Sp itsbergen (78.9 degrees N, 11,9 degrees E). A groundbased Fourier tran sform infrared (FTIR) spectrometer performed these measurements using the Sun as a light source during the summer, and the Moon during the w inter. In situ measurements of C2H2, C2H6, and CCl2F2, made from the t op of a nearby mountain, were combined with the FTIR column data to in fer additional information about the variation of the volume mixing ra tio profiles with altitude and season. The short-lived tropospheric tr ace gases C2H2, C2H6, and CO exhibit large seasonal variations with a summer minimum, caused by reaction with OH. CH2O shows a second maximu m during the summer, caused by its formation by methane oxidation. For the long-lived gases HF, N2O, and CH4 the seasonal cycle is less pron ounced and is forced mainly by wintertime stratospheric diabatic desce nt, which starts in early November and reaches a maximum in March. The total columns of the stratospheric trace gases indicate that the chem ical repartitioning of HCl into ClONO2 starts in November, before the widespread production of polar stratospheric clouds. The total columns of the sum of HCl plus ClONO2 suggests that between December and Marc h they are converted into their active counterparts. Photolysis of HNO 3 gives rise to its summer minimum, and its winter maximum, with no ev idence for a strong winter denitrification.