Validation of ACE-FTS N<sub>2</sub>O measurements

Abstract

Abstract. The Atmospheric Chemistry Experiment (ACE), also known as SCISAT, was launched on 12 August 2003, carrying two instruments that measure vertical profiles of atmospheric constituents using the solar occultation technique. One of these instruments, the ACE Fourier Transform Spectrometer (ACE-FTS), is measuring volume mixing ratio (VMR) profiles of nitrous oxide (N 2 O) from the upper troposphere to the lower mesosphere at a vertical resolution of about 3-4 km. In this study, the quality of the ACE-FTS version 2.2 N 2 O data is assessed through comparisons with Correspondence to: K. Strong (strong@atmosp.physics.utoronto.ca) coincident measurements made by other satellite, balloonborne, aircraft, and ground-based instruments. These consist of vertical profile comparisons with the SMR, MLS, and MIPAS satellite instruments, multiple aircraft flights of ASUR, and single balloon flights of SPIRALE and FIRS-2, and partial column comparisons with a network of groundbased Fourier Transform InfraRed spectrometers (FTIRs). Between 6 and 30 km, the mean absolute differences for the satellite comparisons lie between −42 ppbv and +17 ppbv, with most within ±20 ppbv. This corresponds to relative deviations from the mean that are within ±15%, except for comparisons with MIPAS near 30 km, for which they are as large as 22.5%. Between 18 and 30 km, the mean absolute differences for the satellite comparisons are generally Published by Copernicus Publications on behalf of the European Geosciences Union. within ±10 ppbv. From 30 to 60 km, the mean absolute differences are within ±4 ppbv, and are mostly between −2 and +1 ppbv. Given the small N 2 O VMR in this region, the relative deviations from the mean are therefore large at these altitudes, with most suggesting a negative bias in the ACE-FTS data between 30 and 50 km. In the comparisons with the FTIRs, the mean relative differences between the ACE-FTS and FTIR partial columns (which cover a mean altitude range of 14 to 27 km) are within ±5.6% for eleven of the twelve contributing stations. This mean relative difference is negative at ten stations, suggesting a small negative bias in the ACE-FTS partial columns over the altitude regions compared. Excellent correlation (R=0.964) is observed between the ACE-FTS and FTIR partial columns, with a slope of 1.01 and an intercept of −0.20 on the line fitted to the data.

Multi-year comparisons of ground-based and space-borne Fourier transform spectrometers in the high Arctic between 2006 and 2013

“…Since the mean differences are quite similar for the two different distance criteria, but the correlation is significantly improved, only the mean differences, correlation coefficients, and correlation slopes at a maximum distance of 500 km are considered in the following discussion. This is consistent with many other validation papers which have used 500 km as a limit for coincident measurements for tropospheric species in the high Arctic (e.g., Strong et al, 2008;Viatte et al, 2014). Tightening the distance criteria any further results in very few measurements that are selected for the comparisons.…”

“…The earlier ACE-FTS retrieval version, ACE-FTS v2.2+updates, of these trace gases has previously been validated for most species discussed in this study (O 3 in Dupuy et al, 2009;HCl in Mahieu et al, 2008;HNO 3 in HF in Mahieu et al, 2008;CH 4 in De Mazière et al, 2008; N 2 O in Strong et al, 2008;CO in Clerbaux et al, 2008). In these studies, partial column comparisons between ground-based FTSs and ACE-FTS in the Arctic typically show larger differences than comparisons at lower latitudes.…”

Probability density functions of long-lived tracer observations from satellite in the subtropical barrier region: data intercomparison

“…Extensive comparison among MLS/Aura, MI-PAS/ Envisat and Odin/SMR has been conducted in previous studies, e.g. in Urban et al (2005), Strong et al (2008), Lambert et al (2007). The HALOE instrument was validated against a variety of correlative measurements (e.g.…”

The use of SMILES data to study ozone loss in the Arctic winter 2009/2010 and comparison with Odin/SMR data using assimilation techniques

“…The validation of the N 2 O is reported by Urban et al (2005b). Further comparisons with the Fourier transform spectrometer (FTS) onboard the Atmospheric Chemistry Experiment (ACE) and the Microwave Limb Sounder (MLS) on the Earth Observing System (EOS) Aura satellite are shown by Strong et al (2008) and Lambert et al (2007), respectively. SMR N 2 O agrees with ACE/FTS N 2 O within 7 % between 15 and 30 km (Strong et al, 2008).…”

“…Further comparisons with the Fourier transform spectrometer (FTS) onboard the Atmospheric Chemistry Experiment (ACE) and the Microwave Limb Sounder (MLS) on the Earth Observing System (EOS) Aura satellite are shown by Strong et al (2008) and Lambert et al (2007), respectively. SMR N 2 O agrees with ACE/FTS N 2 O within 7 % between 15 and 30 km (Strong et al, 2008). And SMR N 2 O v2.2 is larger than MLS N 2 O by ∼ 5 % in the pressure range of 68-4.6 hPa and 10 % larger at 100 hPa (Lambert et al, 2007).…”