Airborne observational studies of reactive nitrogen and volatile organic compounds in the upper troposphere and lower stratosphere

Reactive nitrogen (NOy) and volatile organic compounds (VOCs) play important roles in the production and loss of atmospheric ozone. This thesis describes airborne field and laboratory experiment aimed at understanding the budgets of NOy in the polar stratosphere and VOCs in the remote troposphere as they relate to atmospheric ozone. The process of denification, defined as the loss of NOy from air parcels due to the sedimentation HNO3-containing PSCs, prolongs ozone loss in the polar stratospheres. VOCs are involved in ozone production through reactions with NOx and HOx in the troposphere.; During the winter of 1999--2000, a new population of large HNO 3-containing particles was measured in the Arctic polar stratosphere that had a strong potential for denitrification. Particles were examined through a combination of aerosol separation and chemiluminescence measurements of particulate and gas-phase NOy. The detection of these particles, their spatial distributions, the ambient conditions tinder which they were detected, and our methods for interpreting NOy time series with respect to nitric acid trihydrate (NAT) particle sines and number concentrations are discussed. The associated instantaneous gravitational HNO 3 flux values inferred from these particle populations (1 · 10 8 to 5 · 1010{09}molec cm-3 km day-1) are the largest ever derived from in situ measurements. Results indicate that observed column denitrifcation in the 1999--2000 Arctic winter could be caused by most of these populations if continuously formed for 30 days, and that in general more effective denitrifying NAT populations cannot be formed.; The atmospheric budgets of volatile organic compounds (VOCs) were studied using the method of proton-transfer-reaction spectrometry (PTR-MS). In situ observations of VOCs were made in the remote Pacific free troposphere at altitudes up to 14 km. At stratospheric levels of ozone (>300 ppbv) measured acetaldehyde values were particularly high, strongly suggesting the presence of a chemical artifact. Laboratory PTR-MS experiments confirm that, acetaldehyde may be produced in aircraft inlets through heterogeneous reactions of ozone with unsaturated organic compounds. These results suggest that to obtain valid acetaldehyde measurements in future studies, aircraft inlet conditions must be carefully considered.