AIRBORNE MEASUREMENTS OF STRATOSPHERIC CONSTITUENTS OVER THE ARCTIC IN THE WINTER OF 1989

We have used a Fourier transform spectrometer aboard the NASA DC‐8 aircraft during the Airborne Arctic Stratospheric Expedition (AASE) to record infrared absorption spectra of the polar stratosphere. From these high resolution spectra we have derived vertical column amounts above flight altitude of O3, CH4, N2O, H2O, HCl, HF, NO, NO2, ClONO2, and HNO3 for eleven flights poleward of 60°N. We report here measurements on the flight of 26 January 1989 when the flight path during the observations crossed from outside the polar vortex to inside. This allowed a clear comparison of the conditions of the air within the vortex with that outside. Observations of passive tracers such as CH4 and HF indicate that air of a certain composition within the polar vortex occurs at lower altitude than air outside. Within the vortex, we observed markedly reduced columns of HCl and NO2. The ratio of HCl to HF column dropped from its typical nidlatitude value of 4.5 to as low as 1.7 within the vortex, implying that the HCl had been chemically or physically removed from the air in the vortex. NO2 values within the vortex were near 3.0×1014 molecules‐cm−2, about a factor of two less than columns outside. In contrast to the Antarctic observations, HNO3 values were elevated within the vortex. HNO3 columns inside the vortex reached values of 30×1015 molecules‐cm−2. The ClONO2 column was largest within the vortex, peaking at 4×l015 molecules‐cm−2 near the boundary of the vortex, and decreasing farther into the vortex. Copyright 1990 by the American Geophysical Union.