scholarly journals Assessment of the quality of ACE-FTS stratospheric ozone data

2021 ◽  
Author(s):  
Patrick E. Sheese ◽  
Kaley A. Walker ◽  
Chris D. Boone ◽  
Adam E. Bourassa ◽  
Doug A. Degenstein ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Stratospheric Ozone ◽  
Technical Note ◽  
Positive Bias ◽  
Ozone Data ◽  
Negative Drift ◽  
Chemistry Experiment ◽  
Level 2 ◽  
Middle Stratosphere

Abstract. For the past 17 years, the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) instrument on the Canadian SCISAT satellite has been measuring profiles of atmospheric ozone. The latest two operational versions of the level 2 ozone data are versions 3.6 and 4.1. This technical note characterizes how both products compare with correlative data from other limb-sounding satellite instruments, namely MAESTRO, MLS, OSIRIS, SABER, and SMR. In general, v3.6, with respect to the other instruments, exhibits a smaller bias (which is on the order of ~3 %) in the middle stratosphere than v4.1 (~2–9 %), however the bias exhibited in the v4.1 data tends to be more stable, i.e. not changing significantly over time in any altitude region. In the lower stratosphere, v3.6 has a positive bias of about 3–5 % that is stable to within ±1 % dec−1, and v4.1 has a bias on the order of −1 to +5 % and is also stable to within ±1 % dec−1. In the middle stratosphere, v3.6 has a positive bias of ~3 % with a significant negative drift on the order of 0.5–2.5 % dec−1, and v4.1 has a positive bias of 2–9 % that is stable to within ±0.5 % dec−1. However, the v4.1 bias in the middle stratosphere is reduced to 0–5 % after being corrected for field-of-view modelling errors. In the upper stratosphere, v3.6 has a positive bias that increases with altitude up to ~16 % and a significant negative drift on the order of 2–3 % dec−1, and v4.1 has a positive bias that increases with altitude up to ~15 % and is stable to within ±1 % dec−1.

scholarly journals Validation of ozone measurements from the Atmospheric Chemistry Experiment (ACE)

2008 ◽  
Vol 8 (1) ◽  
pp. 2513-2656 ◽  
Author(s):  
E. Dupuy ◽  
K. A. Walker ◽  
J. Kar ◽  
C. D. Boone ◽  
C. T. McElroy ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Near Infrared ◽  
Positive Bias ◽  
Solar Occultation ◽  
Ozone Data ◽  
Significant Difference ◽  
Systematic Effects ◽  
Mean Differences ◽  
Chemistry Experiment ◽  
Satellite Instruments

Abstract. This paper presents extensive validation analyses of ozone observations from the Atmospheric Chemistry Experiment (ACE) satellite instruments: the ACE Fourier Transform Spectrometer (ACE-FTS) and the Measurement of Aerosol Extinction in the Stratosphere and Troposphere Retrieved by Occultation (ACE-MAESTRO) instrument. The ACE satellite instruments operate in the mid-infrared and ultraviolet-visible-near-infrared spectral regions using the solar occultation technique. In order to continue the long-standing record of solar occultation measurements from space, a detailed quality assessment is required to evaluate the ACE data and validate their use for scientific purposes. Here we compare the latest ozone data products from ACE-FTS and ACE-MAESTRO with coincident observations from satellite-borne, airborne, balloon-borne and ground-based instruments, by analysing volume mixing ratio profiles and partial column densities. The ACE-FTS version 2.2 Ozone Update product reports more ozone than most correlative measurements from the upper troposphere to the lower mesosphere. At altitude levels from 16 to 44 km, the mean differences range generally between 0 and +10% with a slight but systematic positive bias (typically +5%). At higher altitudes (45–60 km), the ACE-FTS ozone amounts are significantly larger than those of the comparison instruments by up to ~40% (typically +20%). For the ACE-MAESTRO version 1.2 ozone data product, agreement within ±10% (generally better than ±5%) is found between 18 and 40 km for the sunrise and sunset measurements. At higher altitudes (45–55 km), systematic biases of opposite sign are found between the ACE-MAESTRO sunrise and sunset observations. While ozone amounts derived from the ACE-MAESTRO sunrise occultation data are often smaller than the coincident observations (by as much as −10%), the sunset occultation profiles for ACE-MAESTRO show results that are qualitatively similar to ACE-FTS and indicate a large positive bias (+10 to +30%) in this altitude range. In contrast, there is no significant difference in bias found for the ACE-FTS sunrise and sunset measurements. These systematic effects in the ozone profiles retrieved from the measurements of ACE-FTS and ACE-MAESTRO are being investigated. This work shows that the ACE instruments provide reliable, high quality measurements from the tropopause to the upper stratosphere and can be used with confidence in this vertical domain.

Intercomparison of Odin/SMR ozone measurements with MIPAS and balloon sonde data

2007 ◽  
Vol 85 (11) ◽  
pp. 1111-1123 ◽  
Author(s):  
A Jones ◽  
D Murtagh ◽  
J Urban ◽  
P Eriksson ◽  
J Rösevall
Keyword(s):  
Stratospheric Ozone ◽  
Atmospheric Species ◽  
Ozone Data ◽  
Current Product ◽  
Level 2

The Sub-Millimetre Radiometer (SMR) on board Odin measures various important atmospheric species, including stratospheric ozone. In this study, we compare the three versions (v1.2, v2.0, and v2.1) of level 2 Odin/SMR global stratospheric ozone data to coincident level 2 MIPAS V4.61 and balloon sonde stratospheric ozone data during 2003. The most current product from Odin/SMR (at time of writing), the v2.1, showed the smallest systematic differences when compared to coincident MIPAS and sonde data. Between 17 and 55 km, v2.1 values agreed with MIPAS within 10% (a maximum of 0.42 ppmv), while comparisons to sonde measurements showed an agreement of typically 5–10% between 22 and 35 km (less than 0.5 ppmv below 33 km). Tropical latitudes below 35 km presented the largest absolute systematic differences between v2.1 and sonde coincidences, where Odin/SMR was systematically lower by ~0.9 (more than 10% difference) at approximately 30 km. Comparisons concerning the previous two Odin/SMR versions showed much larger systematic differences, especially at the higher and lower stratospheric altitudes. The main conclusion here is that we suggest that v2.1 of Odin/SMR ozone data should be used for scientific studies. PACS Nos.: 92.60.hd, 95.75.Rs, 95.85.Fm

An evaluation of Odin/OSIRIS limb pointing and stratospheric ozone through comparisons with ozonesondes

2007 ◽  
Vol 85 (11) ◽  
pp. 1125-1141 ◽  
Author(s):  
C A McLinden ◽  
V E Fioletov ◽  
C S Haley ◽  
N Lloyd ◽  
C Roth ◽  
...  
Keyword(s):  
Systematic Uncertainty ◽  
Stratospheric Ozone ◽  
Random Uncertainty ◽  
Data Product ◽  
Ozone Data ◽  
Infrared Imager ◽  
The Tropics ◽  
Middle Stratosphere

Five-plus years of Odin/OSIRIS (Optical Spectrograph and Infrared Imager System) ozone profiles (version 3.0 and SaskMART) have been compared with coincident ozonesonde profiles from the tropopause to the middle stratosphere (~10–35 km). The OSIRIS(v3.0)-sonde comparisons, together with the “knee” technique, suggest that OSIRIS pointing is stable with an accuracy (systematic uncertainty) of 100~m and a precision (random uncertainty) of 400 m. Comparison of coincident profiles revealed excellent overall agreement with differences generally not exceeding 10% between 10 and 35 km. During periods of satellite eclipse larger differences above 25 km were found and concluded to be the result of flexing of the spacecraft frame brought about by cooling. Uncertainties derived from the intercomparison suggest an OSIRIS precision of 25–30% at 10 km, reaching a minimum of about 4–6% in the middle-stratosphere (23–28 km), and 6–8% at 35 km. Ozonesonde uncertainties were also derived and found to be slightly larger in the tropics than mid-latitudes, possibly due to a lack of column normalization at some of the tropical stations. OSIRIS SaskMART ozone, an alternative ozone data product, was found to be very comparable with the v3.0 ozone, with slightly smaller biases relative to the ozonesondes. OSIRIS is concluded to be a robust and accurate source of stratospheric ozone profiles. PACS Nos.: 82.33.Tb, 95.75.Qr, 42.68.–w

scholarly journals Validation of HNO<sub>3</sub>, ClONO<sub>2</sub>, and N<sub>2</sub>O<sub>5</sub> from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS)

2008 ◽  
Vol 8 (13) ◽  
pp. 3529-3562 ◽  
Author(s):  
M. A. Wolff ◽  
T. Kerzenmacher ◽  
K. Strong ◽  
K. A. Walker ◽  
M. Toohey ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Atmospheric Chemistry ◽  
Relative Difference ◽  
Fourier Transform Spectrometer ◽  
Infrared Wavelength ◽  
Key Species ◽  
The Mean ◽  
Chemistry Experiment ◽  
Good Agreement

Abstract. The Atmospheric Chemistry Experiment (ACE) satellite was launched on 12 August 2003. Its two instruments measure vertical profiles of over 30 atmospheric trace gases by analyzing solar occultation spectra in the ultraviolet/visible and infrared wavelength regions. The reservoir gases HNO3, ClONO2, and N2O5 are three of the key species provided by the primary instrument, the ACE Fourier Transform Spectrometer (ACE-FTS). This paper describes the ACE-FTS version 2.2 data products, including the N2O5 update, for the three species and presents validation comparisons with available observations. We have compared volume mixing ratio (VMR) profiles of HNO3, ClONO2, and N2O5 with measurements by other satellite instruments (SMR, MLS, MIPAS), aircraft measurements (ASUR), and single balloon-flights (SPIRALE, FIRS-2). Partial columns of HNO3 and ClONO2 were also compared with measurements by ground-based Fourier Transform Infrared (FTIR) spectrometers. Overall the quality of the ACE-FTS v2.2 HNO3 VMR profiles is good from 18 to 35 km. For the statistical satellite comparisons, the mean absolute differences are generally within ±1 ppbv ±20%) from 18 to 35 km. For MIPAS and MLS comparisons only, mean relative differences lie within±10% between 10 and 36 km. ACE-FTS HNO3 partial columns (~15–30 km) show a slight negative bias of −1.3% relative to the ground-based FTIRs at latitudes ranging from 77.8° S–76.5° N. Good agreement between ACE-FTS ClONO2 and MIPAS, using the Institut für Meteorologie und Klimaforschung and Instituto de Astrofísica de Andalucía (IMK-IAA) data processor is seen. Mean absolute differences are typically within ±0.01 ppbv between 16 and 27 km and less than +0.09 ppbv between 27 and 34 km. The ClONO2 partial column comparisons show varying degrees of agreement, depending on the location and the quality of the FTIR measurements. Good agreement was found for the comparisons with the midlatitude Jungfraujoch partial columns for which the mean relative difference is 4.7%. ACE-FTS N2O5 has a low bias relative to MIPAS IMK-IAA, reaching −0.25 ppbv at the altitude of the N2O5 maximum (around 30 km). Mean absolute differences at lower altitudes (16–27 km) are typically −0.05 ppbv for MIPAS nighttime and ±0.02 ppbv for MIPAS daytime measurements.

scholarly journals Satellite observations of stratospheric hydrogen fluoride and comparisons with SLIMCAT calculations

2015 ◽  
Vol 15 (23) ◽  
pp. 34361-34405 ◽  
Author(s):  
J. J. Harrison ◽  
M. P. Chipperfield ◽  
C. D. Boone ◽  
S. S. Dhomse ◽  
P. F. Bernath ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Transport Model ◽  
Stratospheric Ozone ◽  
Three Dimensional ◽  
Montreal Protocol ◽  
Chemical Transport Model ◽  
Slowing Down ◽  
Rate Of Increase ◽  
Stratospheric Dynamics ◽  
Chemistry Experiment

Abstract. The vast majority of emissions of fluorine-containing molecules are anthropogenic in nature, e.g. chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), and hydrofluorocarbons (HFCs). Many of these fluorine-containing species deplete stratospheric ozone, and are regulated by the Montreal Protocol. Once in the atmosphere they slowly degrade, ultimately leading to the formation of HF, the dominant reservoir of stratospheric fluorine due to its extreme stability. Monitoring the growth of stratospheric HF is therefore an important marker for the success of the Montreal Protocol. We report the comparison of global distributions and trends of HF measured in the Earth's atmosphere by the satellite remote-sensing instruments ACE-FTS (Atmospheric Chemistry Experiment Fourier Transform Spectrometer), which has been recording atmospheric spectra since 2004, and HALOE (HALogen Occultation Experiment), which recorded atmospheric spectra between 1991 and 2005, with the output of SLIMCAT, a state-of-the-art three-dimensional chemical transport model. In general the agreement between observation and model is good, although the ACE-FTS measurements are biased high by ∼ 10 % relative to HALOE. The observed global HF trends reveal a substantial slowing down in the rate of increase of HF since the 1990s: 4.97 ± 0.12 % year-1 (1991–1997; HALOE), 1.12 ± 0.08 % year-1 (1998–2005; HALOE), and 0.52 ± 0.03 % year-1 (2004–2012; ACE-FTS). In comparison, SLIMCAT calculates trends of 4.01, 1.10, and 0.48 % year-1, respectively, for the same periods; the agreement is very good for all but the earlier of the two HALOE periods. Furthermore, the observations reveal variations in the HF trends with latitude and altitude, for example between 2004 and 2012 HF actually decreased in the Southern Hemisphere below ∼ 35 km. SLIMCAT calculations broadly agree with these observations, most notably between 2004 and 2012. Such variations are attributed to variability in stratospheric dynamics over the observation period.

scholarly journals Technical Note: Validation of Odin/SMR limb observations of ozone, comparisons with OSIRIS, POAM III, ground-based and balloon-borne instruments

2008 ◽  
Vol 8 (1) ◽  
pp. 727-779
Author(s):  
F. Jégou ◽  
J. Urban ◽  
J. de La Noë ◽  
P. Ricaud ◽  
E. Le Flochmoën ◽  
...  
Keyword(s):  
Stratospheric Ozone ◽  
Technical Note ◽  
Atmospheric Composition ◽  
Satellite Measurements ◽  
Space Agency ◽  
Infrared Imager ◽  
Ozone Maximum ◽  
Polar Ozone ◽  
Good Agreement

Abstract. The Odin satellite carries two instruments capable of determining stratospheric ozone profiles by limb sounding: the Sub-Millimetre Radiometer (SMR) and the UV-visible spectrograph of the OSIRIS (Optical Spectrograph and InfraRed Imager System) instrument. A large number of ozone profiles measurements were performed during six years from November 2001 to present. This ozone dataset is here used to make quantitative comparisons with satellite measurements in order to assess the quality of the Odin/SMR ozone measurements. In a first step, we compare Swedish SMR retrievals version 2.1, French SMR ozone retrievals version 222 (both from the 501.8 GHz band), and the OSIRIS retrievals version 3.0, with the operational version 4.0 ozone product from POAM III (Polar Ozone Atmospheric Measurement). In a second step, we refine the Odin/SMR validation by comparisons with ground-based instruments and balloon-borne observations. We use observations carried out within the framework of the Network for Detection of Atmospheric Composition Change (NDACC) and balloon flight missions conducted by the Canadian Space Agency (CSA), the Laboratoire de Physique et de Chimie de l'Environnement (LPCE, Orléans, France), and the Service d'Aéronomie (SA, Paris, France). Coincidence criteria were 5° in latitude x in 10° longitude, and 5 h in time in Odin/POAM III comparisons, 12 h in Odin/NDACC comparisons, and 72 h in Odin/balloons comparisons. An agreement is found with the POAM III experiment (10–60 km) within −0.3±0.2 ppmv (bias±standard deviation) for SMR (v222, v2.1) and within −0.5±0.2 ppmv for OSIRIS (v3.0). Odin ozone mixing ratio products are systematically slightly lower than the POAM III data and show an ozone maximum lower by 1–5 km in altitude. The comparisons with the NDACC data (10–34 km for ozonesonde, 10–50 km for lidar, 10–60 for microwave instruments) yield a good agreement within −0.15±0.3 ppmv for the SMR data and −0.3±0.3 ppmv for the OSIRIS data. Finally the comparisons with instruments on large balloons (10–31 km) show a good agreement, within −0.7±1 ppmv.

Internal consistency in the Odin stratospheric ozone products

2007 ◽  
Vol 85 (11) ◽  
pp. 1275-1285 ◽  
Author(s):  
S Brohede ◽  
A Jones ◽  
F Jégou
Keyword(s):  
Infrared Imaging ◽  
Imaging System ◽  
Stratospheric Ozone ◽  
Measurement Techniques ◽  
Data Sets ◽  
Positive Trend ◽  
Error Sources ◽  
Atmospheric Species ◽  
Ozone Data ◽  
Middle Stratosphere

The two independent instruments on the Odin satellite, the Optical Spectrograph and Infrared Imaging System (OSIRIS) and the Sub-Millimetre Radiometer (SMR) produce atmospheric profiles of various atmospheric species including stratospheric ozone. Comparisons are made between OSIRIS version 3.0 and SMR version 2.1 ozone data to evaluate the consistency of the Odin ozone data sets. Results show good agreement between OSIRIS and SMR in the range 25–40 km, where systematic differences are less than 15% for all latitudes and seasons. Larger systematic differences are seen below 25 km, which can be explained by the increase of various error sources and lower signals. The random differences are between 20–30% in the middle stratosphere. Differences between Odin up-scans and down-scans or AM and PM are insignificant in the middle stratosphere. Furthermore, there is little variation from year to year, but a slight positive trend in the differences (OSIRIS minus SMR) of 0.045 ppmv/year at 30 km over validation period (2002–2006). The fact that the two fundamentally different measurement techniques, (absorption spectroscopy of scattering sunlight and emission measurements in the sub-millimetre region) agree so well, provides confidence in the robustness of both techniques.PACS Nos.: 92.60.Hd, 92.75.Rs, 95.55.Fw, 95.55.Jz

scholarly journals Validation of the Atmospheric Chemistry Experiment (ACE) version 2.2 temperature using ground-based and space-borne measurements

2007 ◽  
Vol 7 (4) ◽  
pp. 12463-12539 ◽  
Author(s):  
R. J. Sica ◽  
M. R. M. Izawa ◽  
K. A. Walker ◽  
C. Boone ◽  
S. V. Petelina ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Temperature Profiles ◽  
Fourier Transform Spectrometer ◽  
Upper Troposphere ◽  
Lidar Measurements ◽  
High Bias ◽  
Retrieval Software ◽  
Chemistry Experiment ◽  
Better Than

Abstract. An ensemble of space-borne and ground-based instruments has been used to evaluate the quality of the version 2.2 temperature retrievals from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS). The agreement of ACE-FTS temperatures with other sensors is typically better than 2 K in the stratosphere and upper troposphere and 5 K in the lower mesosphere. There is evidence of a systematic high bias (roughly 3–6 K) in the ACE-FTS temperatures in the mesosphere, and a possible systematic low bias (roughly 2 K) in ACE-FTS temperatures near 23 km. Some ACE-FTS temperature profiles exhibit unphysical oscillations, a problem fixed in preliminary comparisons with temperatures derived using the next version of the ACE-FTS retrieval software. Though these relatively large oscillations in temperature can be on the order of 10 K in the mesosphere, retrieved volume mixing ratio profiles typically vary by less than a percent or so. Statistical comparisons suggest these oscillations occur in about 10% of the retrieved profiles. Analysis from a set of coincident lidar measurements suggests that the random error in ACE-FTS version 2.2 temperatures has a lower limit of about ±2 K.

scholarly journals Summertime free tropospheric ozone pool over the Eastern Mediterranean/Middle East

2013 ◽  
Vol 13 (8) ◽  
pp. 22025-22058 ◽  
Author(s):  
P. Zanis ◽  
P. Hadjinicolaou ◽  
A. Pozzer ◽  
E. Tyrlis ◽  
S. Dafka ◽  
...  
Keyword(s):  
Middle East ◽  
Atmospheric Chemistry ◽  
Tropospheric Ozone ◽  
Eastern Mediterranean ◽  
Stratospheric Ozone ◽  
Surface Ozone ◽  
Eastern Mediterranean Region ◽  
Near Surface ◽  
Ozone Data ◽  
The Mediterranean

Abstract. Observations show that the Mediterranean troposphere is characterized by a marked enhancement in summertime ozone with a maximum over the Eastern Mediterranean. This has been linked to enhanced ozone photochemical production and subsidence under cloud-free anticyclonic conditions. The Eastern Mediterranean region has among the highest levels of background tropospheric ozone around the globe and it can be considered as a global air pollution hotspot. A 12 yr climatological analysis (1998–2009) of free tropospheric ozone was carried out over the region based on ECMWF (European Centre for Medium-Range Weather Forecasts) ERA-interim reanalysis data and simulations with the EMAC (ECHAM5-MESSy for Atmospheric Chemistry) atmospheric chemistry climate model. EMAC is nudged towards the ECMWF analysis data and includes a stratospheric ozone tracer. A characteristic summertime pool with high ozone concentrations is found in the middle troposphere over the Eastern Mediterranean/Middle East (EMME) by ERA-interim ozone data, which is supported by Tropospheric Emission Spectrometer (TES) satellite ozone data and simulations with EMAC. The enhanced ozone over the EMME is a robust feature, propagating down to lower free tropospheric levels. The investigation of ozone in relation to potential vorticity and water vapour and the stratospheric ozone tracer indicates that the dominant mechanism causing the free tropospheric ozone pool is downward transport from the upper troposphere and lower stratosphere associated with the enhanced subsidence and the limited outflow transport that dominates the summertime EMME circulation. The implications of these summertime high free tropospheric ozone values on the seasonal cycle of near surface ozone over the Mediterranean are discussed.

scholarly journals Validation of HNO<sub>3</sub>, ClONO<sub>2</sub>, and N<sub>2</sub>O<sub>5</sub> from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS)

2008 ◽  
Vol 8 (1) ◽  
pp. 2429-2512 ◽  
Author(s):  
M. A. Wolff ◽  
T. Kerzenmacher ◽  
K. Strong ◽  
K. A. Walker ◽  
M. Toohey ◽  
...  
Keyword(s):  
Fourier Transform ◽  
Atmospheric Chemistry ◽  
Relative Difference ◽  
Fourier Transform Spectrometer ◽  
Infrared Wavelength ◽  
Key Species ◽  
The Mean ◽  
Chemistry Experiment ◽  
Good Agreement

Abstract. The Atmospheric Chemistry Experiment (ACE) satellite was launched on 12 August 2003. Its two instruments measure vertical profiles of over 30 atmospheric trace gases by analyzing solar occultation spectra in the ultraviolet/visible and infrared wavelength regions. The reservoir gases HNO3, ClONO2, and N2O5 are three of the key species provided by the primary instrument, the ACE Fourier Transform Spectrometer (ACE-FTS). This paper describes the ACE-FTS version 2.2 data products, including the N2O5 update, for the three species and presents validation comparisons with available observations. We have compared volume mixing ratio (VMR) profiles of HNO3, ClONO2, and N2O5 with measurements by other satellite instruments (SMR, MLS, MIPAS), aircraft measurements (ASUR), and single balloon-flights (SPIRALE, FIRS-2). Partial columns of HNO3 and ClONO2 were also compared with measurements by ground-based Fourier Transform Infrared (FTIR) spectrometers. Overall the quality of the ACE-FTS v2.2 HNO3 VMR profiles is good from 18 to 35 km. For the statistical satellite comparisons, the mean absolute differences are generally within ±1 ppbv (±20%) from 18 to 35 km. For MIPAS and MLS comparisons only, mean relative differences lie within ±10% between 10 and 36 km. ACE-FTS HNO3 partial columns (~15–30 km) show a slight negative bias of −1.3% relative to the ground-based FTIRs at latitudes ranging from 77.8° S–76.5° N. Good agreement between ACE-FTS ClONO2 and MIPAS, using the Institut für Meteorologie und Klimaforschung and Instituto de Astrofísica de Andalucía (IMK-IAA) data processor is seen. Mean absolute differences are typically within ±0.01 ppbv between 16 and 27 km and less than +0.09 ppbv between 27 and 34 km. The ClONO2 partial column comparisons show varying degrees of agreement, depending on the location and the quality of the FTIR measurements. Good agreement was found for the comparisons with the midlatitude Jungfraujoch partial columns for which the mean relative difference is 4.7%. ACE-FTS N2O5 has a low bias relative to MIPAS IMK-IAA, reaching −0.25 ppbv at the altitude of the N2O5 maximum (around 30 km). Mean absolute differences at lower altitudes (16–27 km) are typically −0.05 ppbv for MIPAS nighttime and ±0.02 ppbv for MIPAS daytime measurements.

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