Validation of ACE-FTS version 3.5 NO_y species profiles using correlative satellite measurements

Abstract. The ACE-FTS (Atmospheric Chemistry Experiment – Fourier Transform Spectrometer) instrument on the Canadian SCISAT satellite, which has been in operation for over 12 years, has the capability of deriving stratospheric profiles of many of the NO_y (N + NO + NO₂+ NO₃+ 2  ×  N₂O₅+ HNO₃+ HNO₄+ ClONO₂+ BrONO₂) species. Version 2.2 of ACE-FTS NO, NO₂, HNO₃, N₂O₅, and ClONO₂ has previously been validated, and this study compares the most recent version (v3.5) of these five ACE-FTS products to spatially and temporally coincident measurements from other satellite instruments – GOMOS, HALOE, MAESTRO, MIPAS, MLS, OSIRIS, POAM III, SAGE III, SCIAMACHY, SMILES, and SMR. For each ACE-FTS measurement, a photochemical box model was used to simulate the diurnal variations of the NO_y species and the ACE-FTS measurements were scaled to the local times of the coincident measurements. The comparisons for all five species show good agreement with correlative satellite measurements. For NO in the altitude range of 25–50 km, ACE-FTS typically agrees with correlative data to within −10 %. Instrument-averaged mean relative differences are approximately −10 % at 30–40 km for NO₂, within ±7 % at 8–30 km for HNO₃, better than −7 % at 21–34 km for local morning N₂O₅, and better than −8 % at 21–34 km for ClONO₂. Where possible, the variations in the mean differences due to changes in the comparison local time and latitude are also discussed.