Long term intercomparisons between the Optical Spectrograph and Infra-Red Imager System (OSIRIS) and the Atmospheric Chemistry Experiment (ACE) satellite instruments, and ground-based instruments at the Polar Environment Atmospheric Research Laboratory (PEARL), near Eureka, Nunavut, have been made from 2003 to 2017. The ground-based instruments list can be found here.
Comparison of satellite and ground-based data sets in the high Arctic is challenging. Passive measurements are restricted to the sunlit part of the year, while the large solar zenith angles (SZAs) and small SZA variations pose challenges for both direct-sun and scattered-light instruments. Polar sunrise and sunset create conditions that lead to highly inhomogeneous stratospheric \(NO_2\), while springtime comparisons are affected by the location of the polar vortex. When the polar vortex is strong, it isolates the airmass inside the core and hinders mixing with mid-latitude air. Substantially different trace gas concentrations inside and outside the polar vortex lead to strong gradients across the vortex boundary. Measurements taken in the vicinity of the polar vortex therefore need to be compared with care to account for the spatial variability of ozone and \(NO_2\). In addition to the atmospheric conditions, the harsh Arctic environment and logistical challenges restrict ground-based measurements to a few well-equipped stations; PEARL and Eureka Weather Station (EWS).
The instruments used and their abbreviations as well dataset periods used are given in the table below:
The comparison metrics, coincidence criteria, procedures for extending ozone profiles using ozonesonde data, and for scaling NO2 columns using a photochemical model and the methodology used to assess the long-term consistency of the satellite datasets are described here.
Ozone Results
\(NO_2\) Results
Ozone partial columns from the three satellite instruments show reasonable agreement. OSIRIS and ACE-FTS agree to within 1.2%, while ACE-MAESTRO ozone shows a 6.7% and 5.9% low bias when compared to OSIRIS and ACE-FTS, respectively. Satellite \(NO_2\) partial columns were not compared due to the low number of coincidences beteween OSIRIS and ACE-FTS.
Satellite-plus-sonde ozone columns were compared to five ground-based datatsets. OSIRIS ozone columns agree with ground-based total columns with a maximum mean relative difference of 4.4%. The agreement is better than 7.5% for ACE-FTS ozone, while ACE-MAESTRO columns show a maximum relative difference of 12%, reflecting the low bias indicated by the satellite comparisons. The largest differences were observed for the ACE minus Bruker FTIR and PARIS-IR comparisons. Exluding those four values, all other instrument pairs agree to within 4.4%.
Satellite \(NO_2\) partial columns were compared to four ground-based datasets. OSIRIS partial columns agree with ground-based partial columns to within 19.9%, and the differences show significant seasonal variation, with the largest negative values in the summer. ACE-FTS partial columns show a maximum mean relative difference of 33.2%, that improves to better than 15.3% when excluding the Bruker FTIR comparison.
References
K. Bognar, X. Zhao and K. Strong et al., Updated validation of ACE and OSIRIS ozone and NO2 measurements in the Arctic using ground-based instruments at Eureka, Canada, Journal of Quantitative Spectroscopy & Radiative Transfer, https://doi. org/10.1016/j.jqsrt.2019.07.014, 2019.
D. Griffin, K.A. Walker, S. Conway, F. Kolonjari, K. Strong, R. Batchelor, et al.Multi-year comparisons of ground-based and space-borne fourier transform spectrometers in the high arctic between 2006 and 2013, Atmos Meas Tech, 10 (9) , pp. 3273-3294, 10.5194/amt-10-3273-2017, 2017.
C. Adams, K. Strong, R.L. Batchelor, P.F. Bernath, S. Brohede, C. Boone, et al., Validation of ace and OSIRIS ozone and NO2 measurements using ground based instruments at 80∘ N, Atmos Meas Tech, 5 (5), pp. 927-953, 10.5194/amt-5-927-2012, 2012.
D. Fu, K.A. Walker, R.L. Mittermeier, K. Strong, K. Sung, H. Fast, et al.Simultaneous trace gas measurements using two fourier transform spectrometers at Eureka, Canada during spring 2006, and comparisons with the ACE-FTS, Atmos Chem Phys, 11 (11) , pp. 5383-5405, 10.5194/acp-11-5383-2011, 2011.
R.L. Batchelor, F. Kolonjari, R. Lindenmaier, R.L. Mittermeier, W. Daffer, H. Fast, et al., Four fourier transform spectrometers and the arctic polar vortex: instrument intercomparison and ACE-FTS validation at eureka during the IPY springs of 2007 and 2008, Atmos Meas Tech, 3 (1), pp. 51-66, 10.5194/amt-3-51-2010, 2010.
A. Fraser, F. Goutail, K. Strong, P.F. Bernath, C. Boone, W.H. Daffer, et al., Intercomparison of uv-visible measurements of ozone and NO2 during the Canadian arctic ace validation campaigns: 2004–2006, Atmos Chem Phys, 8 (6), pp. 1763-1788, 10.5194/acp-8-1763-2008, 2008.