Version 4 retrievals for the atmospheric chemistry experiment Fourier transform spectrometer (ACE-FTS) and imagers

Boone, Christopher D.; Bernath, P. F.; Cok, David R.; Jones, Scott C.; Steffen, J.

doi:10.1016/j.jqsrt.2020.106939

Cited by 111 publications

(129 citation statements)

References 27 publications

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“…In particular, CO concentrations are retrieved from the roto-vibrational absorption bands around 4.7µm (v = 1 → 0) and 2.3µm (v = 2 → 0). CO retrievals are performed between 5 and 105 km altitude, with a 3-4 km vertical resolution (Boone et al, 2005(Boone et al, , 2013. In this study we use ACE-FTS v3.6 dataset for comparison.…”

Section: Ace-ftsmentioning

confidence: 99%

Recovery and validation of Odin/SMR long term measurements ofmesospheric carbon monoxide

Grieco¹,

Pérot²,

Murtagh³

et al. 2020

Preprint

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Abstract. The Sub-Millimetre Radiometer (SMR) on board the Odin satellite performs limb sounding measurements of the middle atmosphere to detect molecular emission from different species. Carbon monoxide (CO) is an important tracer of atmospheric dynamics at these altitudes, due to its long photochemical lifetime and high vertical concentration gradient. In this study, we have successfully recovered over 18 years of SMR observations, providing the only dataset to date being so extended in time and stretching out to the polar regions, with regards to satellite-measured mesospheric CO. This new dataset is part of the Odin/SMR version 3.0 level 2 data. The much of the level 1 dataset – except the October 2003 to October 2004 period – was affected by a malfunctioning of the Phase-Lock Loop (PLL) in the frontend used for CO observations. Because of this technical issue, the CO line could be shifted away from its normal frequency location causing the retrieval to fail or leading to an incorrect estimation of the CO concentration. An algorithm was developed to locate the CO line and shift it to its correct location. Nevertheless, another artifact causing an underestimation of the concentration, i.e. a line broadening, stemmed from the PLL malfunctioning. This was accounted for by using a broader response function. The application of these corrections resulted in the recovery of a large amount of data that was previously being flagged as problematic and therefore not processed. A validation study has been carried out, showing how SMR CO volume mixing ratios are in general in good accordance with the other instruments considered in the study. Overall, the agreement is very good between 60 and 80 km altitude, with relative differences close to zero. A positive bias at low altitudes (50–60 km) up to +20 % and a negative bias up to −20 % at high altitudes (80–100 km) were found with respect to the compared instruments.

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Section: Ace-ftsmentioning

confidence: 99%

Recovery and validation of Odin/SMR long term measurements ofmesospheric carbon monoxide

Grieco¹,

Pérot²,

Murtagh³

et al. 2020

Preprint

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“…Its inclined circular orbit provides up to 30 measurements (sunrise and sunset) per day with a focus on the high latitudes. We used the ACE-FTS version 3.6 dataset which provides profiles of temperature and more than 30 trace gases (Boone et al, 2013). The vertical resolution of these measurements is 3 km based on the instrument field-of-view (Boone et al, 2005).…”

Section: Ace-ftsmentioning

confidence: 99%

Technical note: Reanalysis of Aura MLS Chemical Observations

Errera¹,

Chabrillat²,

Christophe³

et al. 2019

Preprint

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Abstract. This paper presents a reanalysis of the atmospheric chemical composition from the upper troposphere to the lower mesosphere from August 2004 to December 2017. This reanalysis is produced by the Belgian Assimilation System for Chemical ObsErvations (BASCOE) constrained by the chemical observations from the Microwave Limb Sounder (MLS) onboard the Aura satellite. BASCOE is based on the Ensemble Kalman Filter (EnKF) method and includes a chemical transport model driven by the winds and temperature from the ERA-Interim meteorological reanalysis. The model resolution is 3.75&#176; in longitude, 2.5&#176; in latitude and 37 vertical levels from the surface to 0.1&#8201;hPa with 25 levels above 100&#8201;hPa. The outputs are provided every 6 hours. This reanalysis is called BRAM2 for BASCOE Reanalysis of Aura MLS, version 2. Vertical profiles of eight species from MLS version 4 are assimilated and are evaluated in this paper: ozone (O3), water vapour (H2O), nitrous oxide (N2O), nitric acid (HNO3), hydrogen chloride (HCl), chlorine oxide (ClO), methyl chloride (CH3Cl) and carbon monoxide (CO). They are evaluated using independent observations from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACEFTS), the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES), N2O observations from another MLS radiometer than the one used to deliver the standard product and ozonesondes. The evaluation is done in four regions of interest where only selected species are evaluated. These regions are (1) the lower stratospheric polar vortex where O3, H2O, N2O, HNO3, HCl and ClO are evaluated, (2) the upper stratospheric lower mesospheric polar vortex where H2O, N2O, HNO3 and CO are evaluated, (3) the tropical tropopause layer (TTL) where O3, H2O, CO and CH3Cl are evaluated and (4) the middle stratosphere where O3, H2O, N2O, HNO3, HCl, ClO and CH3Cl are evaluated. In general BRAM2 reproduces MLS observations within their uncertainties and agrees well with independent observations, with several limitations discussed in this paper (see the summary in Sect. 5.5). In particular, ozone is not assimilated at altitudes above (i.e. pressures lower than) 4&#8201;hPa due to a model bias that cannot be corrected by the assimilation. MLS ozone profiles display unphysical oscillations in the TTL which are corrected by the assimilation, allowing a good agreement with ozonesondes. Moreover, in the upper troposphere, comparison of BRAM2 with MLS and independent observations suggests a positive bias in MLS O3 and a negative bias in MLS H2O. The reanalysis also reveals a drift in MLS N2O against independent observations which highlights the potential use of BRAM2 to estimate biases between instruments. BRAM2 is publicly available and will be extended to assimilate MLS observations post 2017.

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“…We use the most recent version 3.6 of the ACE-FTS data (Boone et al, 2013) and apply filters to remove physically unrealistic outliers from the data (Sheese et al, 2015). Even after the screening, we found large anomalies for several ACE profiles in the tropical UTLS (< 18 km) that led to significantly greater noise in the comparisons.…”

Section: Ace-ftsmentioning

confidence: 99%

Response to Referee 1

Kramarova¹

2018

Preprint

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Version 4 retrievals for the atmospheric chemistry experiment Fourier transform spectrometer (ACE-FTS) and imagers

Cited by 111 publications

References 27 publications

Recovery and validation of Odin/SMR long term measurements ofmesospheric carbon monoxide

Recovery and validation of Odin/SMR long term measurements ofmesospheric carbon monoxide

Technical note: Reanalysis of Aura MLS Chemical Observations

Response to Referee 1

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