A global inventory of stratospheric NO y from ACE‐FTS

The Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE‐FTS) on board the Canadian SCISAT‐1 satellite (launched in August 2003) measures over 30 different atmospheric species, including six nitrogen trace gases that are needed to quantify the stratospheric NO y budget. We combine volume mixing ratio (VMR) profiles for NO, NO 2 , HNO 3 , N 2 O 5 , ClONO 2 , and HNO 4 to determine a zonally averaged NO y climatology on monthly and 3 month combined means (December–February, March–May, June–August, and September–November) at 5° latitude spacing and on 33 pressure surfaces. Peak NO y VMR concentrations (15–20 ppbv) are situated at about 3 hPa (∼40 km) in the tropics, while they are typically lower at about 10 hPa (∼30 km) in the midlatitudes. Mean NO y VMRs are similar in both the northern and southern polar regions, with the exception of large enhancements periodically observed in the upper stratosphere and lower mesosphere. These are primarily due to enhancements of NO due to energetic particle precipitation and downward transport. Other features in the NO y budget are related to descent in the polar vortex, heterogeneous chemistry, and denitrification processes. Comparison of the ACE‐FTS NO y budget is made to both the Odin and ATMOS NO y data sets, showing in both cases a good level of agreement, such that relative differences are typically better than 20%. The NO y climatological products are available through the ACE website and are a supplement to the paper.