Ozone vertical profiles from TGO/NOMAD-UVIS: an inter-comparison of three retrieval schemes

2021 ◽  
Author(s):  
Arianna Piccialli ◽  
Ann Carine Vandaele ◽  
Yannick Willame ◽  
Shohei Aoki ◽  
Cedric Depiesse ◽  
...  
Keyword(s):  
Local Density ◽  
Estimation Method ◽  
Optimal Estimation ◽  
Space Science ◽  
Solar Occultation ◽  
Retrieval Scheme ◽  
Local Densities ◽  
The Vertical Distribution ◽  
Applied Optics ◽  
Infrared Channel

<p>We will present the vertical distribution of <strong>ozone</strong> obtained from <strong>NOMAD-UVIS solar occultations</strong> and we will compare the results of three retrieval schemes.</p><p><strong>NOMAD</strong> (Nadir and Occultation for MArs Discovery) is a spectrometer composed of 3 channels: 1) a solar occultation channel (SO) operating in the infrared (2.3-4.3 μm); 2) a second infrared channel LNO (2.3-3.8 μm) capable of doing nadir, as well as solar occultation and limb; and 3) an ultraviolet/visible channel <strong>UVIS</strong> (200-650 nm) that can work in the three observation modes [1,2].</p><p>The UVIS channel has a spectral resolution <1.5 nm. In the solar occultation mode it is mainly devoted to study the climatology of <strong>ozone</strong> and <strong>aerosols</strong> content [3].</p><p>Since the beginning of operations, on 21 April 2018, NOMAD UVIS acquired more than 4000 solar occultations with an almost complete coverage of the planet.</p><p>NOMAD-UVIS spectra are simulated using three different retrieval scheme:</p><p>1) An onion peeling approach based on [4,5] deriving slant columns at the different altitudes sounded, from which local densities are obtained;</p><p>2) The line-by-line radiative transfer code ASIMUT-ALVL developed at IASB-BIRA [6] using the Optimal Estimation Method to derive the local density profile in one go (on all transmittances of one occultation observation);</p><p>3) A direct onion peeling method deriving sequentially from top to bottom the local densities in the different layers probed.</p><p>We will compare results obtained from the different retrieval methods as well as their uncertainties and we will discuss the advantages and difficulties of each method.</p><p><strong>References</strong></p><p>[1] Vandaele, A.C., et al., Planetary and Space Science, Vol. 119, pp. 233–249, 2015.</p><p>[2] Neefs, E., et al., Applied Optics, Vol. 54 (28), pp. 8494-8520, 2015.</p><p>[3] M.R. Patel et al., In: Appl. Opt. 56.10 (2017), pp. 2771–2782. DOI: 10.1364/AO.56.002771.</p><p>[4] Quémerais, E.,et al. J.Geophys. Res. (Planets)111, 9, 2006.</p><p>[5] Piccialli, A. et al., Planetary and Space Science, 113-114(2015) 321–335</p><p>[6] Vandaele, A.C., et al., JGR, 2008. 113 doi:10.1029/2008JE003140.</p>

scholarly journals Solar occultation with SCIAMACHY: algorithm description and first validation

2005 ◽  
Vol 5 (1) ◽  
pp. 17-66 ◽  
Author(s):  
J. Meyer ◽  
A. Bracher ◽  
A. Rozanov ◽  
A. C. Schlesier ◽  
H. Bovensmann ◽  
...  
Keyword(s):  
Vertical Profile ◽  
Estimation Method ◽  
Optimal Estimation ◽  
Trace Gas ◽  
Transmission Spectra ◽  
Atmospheric Transmission ◽  
Gas Concentration ◽  
Solar Occultation ◽  
First Results ◽  
The Vertical Distribution

Abstract. This presentation concentrates on solar occultation measurements with the spaceborne spectrometer SCIAMACHY in the UV-Vis wavelength range. Solar occultation measurements provide unique information about the vertical distribution of atmospheric constituents. For retrieval of vertical trace gas concentration profiles, an algorithm has been developed based on the optimal estimation method. The forward model is capable to simulate the extinction signals of different species as they occur in atmospheric transmission spectra obtained from occultation measurements. Furthermore, correction algorithms have been implemented to address shortcomings of the tangent height pre-processing and inhomogeneities of measured solar spectra. First results of O3 and NO2 vertical profile retrievals have been validated with data from ozone sondes and satellite based occultation instruments. The validation shows very promising results for SCIAMACHY O3 and NO2 values between 15 to 35 km with errors in the order of 10% and 15%, respectively.

Update on CO2 and temperature profiles retrievals from NOMAD-SO on board ExoMars TGO

2021 ◽  
Author(s):  
Loïc Trompet ◽  
Ann Carine Vandaele ◽  
Shohei Aoki ◽  
Justin Erwin ◽  
Ian Thomas ◽  
...  
Keyword(s):  
Local Density ◽  
Regularization Parameter ◽  
Estimation Method ◽  
Diffraction Order ◽  
Tunable Filter ◽  
Fine Tuning ◽  
Temperature Profiles ◽  
Transfer Program ◽  
Solar Occultation ◽  
Retrieval Scheme

<ul> <li>The SO channel of the NOMAD instrument</li> </ul> <p>The NOMAD-SO channel [1] is an infrared spectrometer working in the 2.2 to 4.3 µm spectral range (2200-4500 cm<sup>-1</sup>) and started to perform solar occultation measurement on April 21, 2018. The instrument is composed of an echelle grating coupled to an Acousto-Optical Tunable Filter for the diffraction order selection. As TGO is on a quasi-circular orbit at around 400 km of altitude, it performs one orbit every two hours. During a solar occultation measurement, SO scans six diffraction orders each second. These diffraction orders are recorded on four bins leading to a vertical sampling lower than one km. The calibration of the SO channel is described in [2] and is still being fine-tuned.</p> <ul> <li>CO<sub>2</sub> density and temperature profiles retrievals</li> </ul> <p>Several diffraction orders probe different altitude ranges as they contain CO<sub>2</sub> lines with different intensities that appear and saturate at different altitudes. Correct temperature profiles are necessary for the retrieval of several species and the profiles have to be carefully retrieved as their inversion is very sensitive to noise. We use the following retrieval scheme:</p> <p>For each solar occultation measurement, we derive a slant column profile of CO<sub>2</sub> using ASIMUT-ALVL [3]. ASIMUT is a radiative transfer program developed at BIRA-IASB and uses the Optimal Estimation Method for regularization [4]. The GEM-Mars GCM provides the <em>a priori</em> profiles of CO<sub>2</sub> local density, pressure and temperature. We then apply an iterated Tikhonov regularization to derive a regularized local density profile using an improved version of the algorithm described in [5]. This method requires the selection of a regularization parameter to reduce as much as possible the presence of noise in the profile while keeping the real variations. This retrieval scheme allows a fine-tuning of the reguralization parameter. We finally apply the hydrostatic equilibrium equation to derive the temperature profiles [6]. We derived the NOMAD-SO CO<sub>2</sub> and temperature profiles for MY34 and 35.</p>

scholarly journals Solar occultation with SCIAMACHY: algorithm description and first validation

2005 ◽  
Vol 5 (6) ◽  
pp. 1589-1604 ◽  
Author(s):  
J. Meyer ◽  
A. Bracher ◽  
A. Rozanov ◽  
A. C. Schlesier ◽  
H. Bovensmann ◽  
...  
Keyword(s):  
Vertical Profile ◽  
Estimation Method ◽  
Optimal Estimation ◽  
Trace Gas ◽  
Transmission Spectra ◽  
Atmospheric Transmission ◽  
Gas Concentration ◽  
Solar Occultation ◽  
First Results ◽  
The Vertical Distribution

Abstract. This presentation concentrates on solar occultation measurements with the spaceborne spectrometer SCIAMACHY in the UV-Vis wavelength range. Solar occultation measurements provide unique information about the vertical distribution of atmospheric constituents. For retrieval of vertical trace gas concentration profiles, an algorithm has been developed based on the optimal estimation method. The forward model is capable of simulating the extinction signals of different species as they occur in atmospheric transmission spectra obtained from occultation measurements. Furthermore, correction algorithms have been implemented to address shortcomings of the tangent height pre-processing and inhomogeneities of measured solar spectra. First results of O3 and NO2 vertical profile retrievals have been validated with data from ozone sondes and satellite based occultation instruments. The validation shows very promising results for SCIAMACHY O3 and NO2 values between 15 to 35km with errors of the order of 10% and 15%, respectively.

scholarly journals Global carbon monoxide vertical distributions from spaceborne high-resolution FTIR nadir measurements

2005 ◽  
Vol 5 (11) ◽  
pp. 2901-2914 ◽  
Author(s):  
B. Barret ◽  
S. Turquety ◽  
D. Hurtmans ◽  
C. Clerbaux ◽  
J. Hadji-Lazaro ◽  
...  
Keyword(s):  
High Resolution ◽  
Estimation Method ◽  
Lower Troposphere ◽  
Optimal Estimation ◽  
Vertical Distributions ◽  
Surface Measurements ◽  
The Vertical Distribution ◽  
Global Carbon ◽  
Good Agreement

Abstract. This paper presents the first global distributions of CO vertical profiles retrieved from a thermal infrared FTS working in the nadir geometry. It is based on the exploitation of the high resolution and high quality spectra measured by the Interferometric Monitor of Greenhouse gases (IMG) which flew onboard the Japanese ADEOS platform in 1996-1997. The retrievals are performed with an algorithm based on the Optimal Estimation Method (OEM) and are characterized in terms of vertical sensitivity and error budget. It is found that most of the IMG measurements contain between 1.5 and 2.2 independent pieces of information about the vertical distribution of CO from the lower troposphere to the upper troposphere-lower stratosphere (UTLS). The retrievals are validated against coincident NOAA/CMDL in situ surface measurements and NDSC/FTIR total columns measurements. The retrieved global distributions of CO are also found to be in good agreement with the distributions modeled by the GEOS-CHEM 3D CTM, highlighting the ability of IMG to capture the horizontal as well as the vertical structure of the CO distributions.

scholarly journals Droplet vertical sizing in warm clouds using passive optical measurements from a satellite

2012 ◽  
Vol 5 (3) ◽  
pp. 517-528 ◽  
Author(s):  
A. Kokhanovsky ◽  
V. V. Rozanov
Keyword(s):  
Vertical Profile ◽  
Estimation Method ◽  
Optimal Estimation ◽  
Effective Radius ◽  
Optical Measurements ◽  
Weighting Functions ◽  
Near Ir ◽  
Cloud Optical Thickness ◽  
The Vertical Distribution

Abstract. In this paper a new algorithm for the determination of the vertical distribution of the droplet effective radius in shallow warm clouds is proposed. The method is based on the fact that the spectral top-of-atmosphere reflectance in the near IR spectral range depends on the vertical profile of the effective radius of droplets. The retrieval is based on the optimal estimation method and direct radiative transfer calculations of respective weighting functions. The applications of the method both to synthetic and satellite data are presented. An important feature of the method is the fact that the cloud optical thickness and cloud effective radius are found using the standard homogeneous cloud retrieval and then the retrievals are improved assuming the type of the droplet effective radius profile.

scholarly journals H<sub>2</sub><sup>16</sup>O and HDO measurements with IASI/MetOp

2009 ◽  
Vol 9 (2) ◽  
pp. 9267-9290 ◽  
Author(s):  
H. Herbin ◽  
D. Hurtmans ◽  
C. Clerbaux ◽  
L. Clarisse ◽  
P.-F. Coheur
Keyword(s):  
Water Vapour ◽  
Estimation Method ◽  
Optimal Estimation ◽  
Temporal Variations ◽  
Radiative Transfer Model ◽  
Transfer Model ◽  
Inversion Procedure ◽  
Spatio Temporal ◽  
The Vertical Distribution

Abstract. In this paper we analyze distributions of water vapour isotopologues in the troposphere using infrared spectra recorded by the Infrared Atmospheric Sounding Interferometer (IASI), which operates onboard the Metop satellite in nadir geometry. The simultaneous uncorrelated retrieval of H216O and HDO was performed on radiance measurements using a line-by-line radiative transfer model and an inversion procedure based on the Optimal Estimation Method (OEM). The characterizations of the retrieved products in terms of vertical sensitivity and error budgets show that IASI measurements contain up to 6 independent pieces of information on the vertical distribution of H216O and up to 3.5 for HDO from the surface up to the upper troposphere (0–20 km). The H216O retrieved profiles are in good agreement with local sonde measurements at different latitudes during different times of the year. Our results demonstrate the ability of the IASI instrument to monitor atmospheric isotopologic water vapour distributions with unprecedented sensitivity. As a case study, we analyse concentration distributions and spatio-temporal variations of H216O and HDO during the October 2007 Krosa super-typhoon over South-East Asia and show with this example the IASI potential to capture variations in the HDO/H216O isotopologic ratio values over space and time.

scholarly journals Retrieval and validation of MetOp/IASI methane

2017 ◽  
Vol 10 (12) ◽  
pp. 4623-4638 ◽  
Author(s):  
Evelyn De Wachter ◽  
Nicolas Kumps ◽  
Ann Carine Vandaele ◽  
Bavo Langerock ◽  
Martine De Mazière
Keyword(s):  
Estimation Method ◽  
Correlation Coefficients ◽  
Principal Component ◽  
Optimal Estimation ◽  
Good Sensitivity ◽  
Total Uncertainty ◽  
Upper Troposphere ◽  
The Difference ◽  
Mean Differences ◽  
The Vertical Distribution

Abstract. A new IASI methane product developed at the Royal Belgian Institute for Space Aeronomy (BIRA-IASB) is presented. The retrievals are performed with the ASIMUT-ALVL software based on the optimal estimation method (OEM). This paper gives an overview of the forward model and retrieval concept. The usefulness of reconstructed principal component compressed (PCC) radiances is highlighted. The information content study carried out in this paper shows that most IASI pixels contain between 0.9 and 1.6 independent pieces of information about the vertical distribution of CH4, with a good sensitivity in the mid- to upper troposphere. A detailed error analysis was performed. The total uncertainty is estimated to be 3.73 % for a CH4 partial column between 4 and 17 km. An extended validation with ground-based CH4 observations at 10 locations was carried out. IASI CH4 partial columns are found to correlate well with the ground-based data for 6 out of the 10 Fourier transform infrared (FTIR) stations with correlation coefficients between 0.60 and 0.84. Relative mean differences between IASI and FTIR CH4 range between −2.31 and 4.04 % and are within the systematic uncertainty. For 6 out of the 10 stations the relative mean differences are smaller than ±1 %. The standard deviation of the difference lies between 1.76 and 2.97 % for all the stations.

scholarly journals Quality assessment of ground-based microwave measurements of chlorine monoxide, ozone, and nitrogen dioxide from the NDSC radiometer at the Plateau de Bure

2004 ◽  
Vol 22 (6) ◽  
pp. 1903-1915 ◽  
Author(s):  
P. Ricaud ◽  
P. Baron ◽  
J. de La Noë
Keyword(s):  
Microwave Radiometer ◽  
Estimation Method ◽  
Optimal Estimation ◽  
Temporal Variations ◽  
Data Sets ◽  
Site Location ◽  
Data Set ◽  
Chlorine Monoxide ◽  
Slow Drift ◽  
Retrieval Scheme

Abstract. A ground-based microwave radiometer dedicated to chlorine monoxide (ClO) measurements around 278GHz has been in operation from December 1993-June 1996 at the Plateau de Bure, France (45° N, 5.9° E, 2500m altitude). It belongs to the international Network for the Detection of Stratospheric Change. A detailed study of both measurements and retrieval schemes has been undertaken. Although dedicated to the measurements of ClO, simultaneous profiles of O3, ClO and NO2, together with information about the instrumental baseline, have been retrieved using the optimal estimation method. The vertical profiles have been compared with other ground-based microwave data, satellite-borne data and model results. Data quality shows: 1) the weak sensitivity of the instrument that obliges to make time averages over several hours; 2) the site location where measurements of good opacities are possible for only a few days per year; 3) the baseline undulation affecting all the spectra, an issue common to all the microwave instruments; 4) the slow drift of some components affecting frequencies by 3-4MHz within a couple of months. Nevertheless, when temporally averaging data over a few days, ClO temporal variations (diurnal and over several weeks in winter 1995) from 35-50km are consistent with model results and satellite data, particularly at the peak altitude around 40km, although temporal coincidences are infrequent in winter 1995. In addition to ClO, it is possible to obtain O3 information from 30-60km whilst the instrument is not optimized at all for this molecule. Retrievals of O3 are reasonable when compared with model and another ground-based data set, although the lowermost layers are affected by the contamination of baseline remnants. Monthly-averaged diurnal variations of NO2 are detected at 40km and appear in agreement with photochemical model results and satellite zonally-averaged data, although the amplitude is weaker than the other data sets. This NO2 result highlights the great potential of the retrieval scheme used.

scholarly journals Information operator approach applied to the retrieval of the vertical distribution of atmospheric constituents from ground-based high-resolution FTIR measurements

2012 ◽  
Vol 5 (1) ◽  
pp. 161-180 ◽  
Author(s):  
C. Senten ◽  
M. De Mazière ◽  
G. Vanhaelewyn ◽  
C. Vigouroux
Keyword(s):  
Vertical Distribution ◽  
Tikhonov Regularization ◽  
Estimation Method ◽  
Optimal Estimation ◽  
Atmospheric Composition ◽  
High Spectral Resolution ◽  
Retrieval Algorithm ◽  
Operator Approach ◽  
Information Operator ◽  
The Vertical Distribution

Abstract. The analysis of high spectral resolution Fourier Transform infrared (FTIR) solar absorption spectra is an important issue in remote sensing. If this is done carefully, one can obtain information, not only about the total column abundances, but also about the vertical distribution of various constituents in the atmosphere. This work introduces the application of the information operator approach for extracting vertical profile information from ground-based FTIR measurements. The algorithm is implemented and tested within the well-known retrieval code SFIT2, adapting the optimal estimation method such as to take into account only the significant contributions to the solution. In particular, we demonstrate the feasibility of the method in an application to ground-based FTIR spectra taken in the framework of the Network for the Detection of Atmospheric Composition Change (NDACC) at Ile de La Réunion (21° S, 55° E). A thorough comparison is made between the original optimal estimation method, Tikhonov regularization and this alternative retrieval algorithm, regarding information content, retrieval robustness and corresponding full error budget evaluation for the target species ozone (O3), nitrous oxide (N2O), methane (CH4), and carbon monoxide (CO). It is shown that the information operator approach performs well and in most cases yields both a better accuracy and stability than the optimal estimation method. Additionally, the information operator approach has the advantage of being less sensitive to the choice of a priori information than the optimal estimation method and Tikhonov regularization. On the other hand, in general the Tikhonov regularization results seem to be slightly better than the optimal estimation method and information operator approach results when it comes to error budgets and column stability.

scholarly journals Information operator approach applied to the retrieval of the vertical distribution of atmospheric constituents from ground-based high-resolution FTIR measurements

2011 ◽  
Vol 4 (3) ◽  
pp. 3739-3785
Author(s):  
C. Senten ◽  
M. De Mazière ◽  
G. Vanhaelewyn ◽  
C. Vigouroux
Keyword(s):  
Vertical Distribution ◽  
Tikhonov Regularization ◽  
Estimation Method ◽  
Optimal Estimation ◽  
High Spectral Resolution ◽  
Tikhonov Regularization Method ◽  
Retrieval Algorithm ◽  
Operator Approach ◽  
Information Operator ◽  
The Vertical Distribution

Abstract. The analysis of high spectral resolution Fourier Transform infrared (FTIR) solar absorption spectra is an important issue in remote sensing. If this is done carefully, one can obtain information, not only about the total column abundances, but also about the vertical distribution of various constituents in the atmosphere. This work introduces the application of the information operator approach for extracting vertical profile information from ground-based FTIR measurements. The algorithm is implemented and tested within the well-known retrieval code SFIT2, adapting the optimal estimation method such as to take into account only the significant contributions to the solution. In particular, we demonstrate the feasibility of the method in an application to ground-based FTIR spectra taken in the frame of the Network for the Detection of Atmospheric Composition Change (NDACC) at Ile de La Réunion (21° S, 55° E). A thorough comparison is made between the original optimal estimation method and this alternative retrieval algorithm, regarding information content, retrieval robustness and corresponding full error budget evaluation for the target species ozone (O3), nitrous oxide (N2O), methane (CH4), and carbon monoxide (CO). For O3 and CH4, a comparison with the Tikhonov regularization method has also been made. It is shown that the information operator approach performs well and in most cases yields both a better accuracy and stability than the optimal estimation method. Additionally, the information operator approach has the advantage of being less sensitive to the choice of a priori information. The Tikhonov regularization results seem to be situated between both methods' results, as to profile retrievals, error budgets and column stability.

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