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Retrieving global observations of gravity waves (GW) from recent satellite missions is challenging. Nadir viewing satellites such as AIRS provide directional momentum fluxes, but lack fine vertical resolution and hence observe only those GW with exceptionally high intrinsic phase speed. Limb scanning instruments such as HIRDLS and SABER have only a single measurement track and hence provide only an estimate of absolute GW momentum flux. In addition, the sparse along-track sampling of these limb sounders introduce uncertainties in horizontal wavelength. GPS-RO can provide GW profile triplets, allowing in principle the horizontal direction of GW propagation to be inferred, but these triplets are rare. Finally, direct wind measurements from Aeolus are restricted in altitude to less than ~25km and only provide the wind component in the direction of the lidar beam from one observational track. In consequence, also Aeolus cannot reveal horizontal propagation direction and GW momentum flux.This situation could be dramatically improved by bringing a limb imager into space. A limb imager combines the very dense spatial sampling of a nadir viewing instrument with the high vertical resolution of a limb sounder. This will provide an almost complete description of the vertical spectrum of GWs, necessary for inferring drag estimates. Such global GW momentum flux data would for the first time allow to retrieve a global momentum budget from the mid-troposphere to the upper mesosphere.The changing-atmosphere infra-Red Tomography (CAIRT) mission candidate for ESA's earth explorer 11 proposes a limb imager for spatial sampling of 25 km across-track, 50 km along-track and 1 km in the vertical. From this we expect to infer directional GW momentum fluxes from the tropopause to 70 km or higher. This will allow longstanding scientific questions to be addressed such as the quantification of tropospheric GW sources and their related phase speed spectra and the identification of secondary wave generation in the stratosphere and lower mesosphere. Considering the momentum flux at higher altitudes, secondary wave generation competes with oblique GW propagation which allows GWs from low latitude sources to reach the high latitudes mesosphere and thus avoid critical levels. In general, two-way interaction with the background flow will be considered via the modulation of the GW spectrum by the winds and the mean wind accelerations by the GWs. In this contribution we will outline the CAIRT instrument concept, give an overview of the mission’s objectives and demonstrate its potential using simulated observations.

The region separating the inner and outer radiation belt, typically devoid of energetic electrons, is termed the slot region. The outer edge of the slot region marks the equatorward edge of the energetic electron precipitation (EEP) originating from the outer radiation belt. Its varying location is strongly linked to the plasmasphere and geomagnetic activity. As such, geomagnetic indices are used to estimate the equatorward extent of the EEP region. There are, however, numerous reports where the energetic electrons cross these boundaries and fill the slot region, during which energetic electrons that can precipitate into the atmosphere long after the geomagnetic activity subsides. This is a missing source of energy input in current EEP estimates based on geomagnetic indices.This study explores the occurrence rate, reformation, local time dependence, and energy deposition of slot region filling events. Medium energy electron measurements from the NOAA/POES over a full solar cycle from 2004 to 2014 are applied. We combine observations from the MEPED 0° and 90° detectors together with theory of pitch angle diffusion by wave-particle interaction to estimate the precipitating fluxes. To explore the energy dependent characteristics, each of the MEPED energy channels, > 43, >114, and >292 keV are evaluated independently. Finally, we investigate the potential EEP impact on the NO density utilizing seven years of Envisat MIPAS NO observations from 2005 to 2011.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited., A new global O3 data product retrieved from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) spectra with the IMK–IAA MIPAS data processor has been released. These data are based on ESA version 8 recalibrated radiance spectra with improved temporal stability. Changes in the level-2 processing with respect to previous data versions include the following: (1) the retrievals use improved temperature data and thus suffer less from the propagation of related errors. (2) The background continuum is now considered up to 58 km. (3) A priori information is now used to constrain the retrieval of the radiance offset. (4) Water vapour is fitted jointly with ozone to minimize the impact of interfering water lines. (5) A more adequate regularization has been chosen. (6) Ozone absorption lines in the MIPAS A band (685–980 cm−1) are used almost exclusively because of inconsistencies in spectroscopic data in the MIPAS AB band (1010–1180 cm−1). Only at altitudes above 50 km, where A-band ozone lines do not provide sufficient information, are ozone lines in the MIPAS AB band used. (7) Temperature-adjusted climatologies of vibrational temperatures of O3 and CO2 are considered to account for non-local thermodynamic equilibrium radiation. Ozone errors are estimated to be less than 10 % in the altitude range 20–50 km. The error budget is dominated by the spectroscopic errors, followed by the uncertainty of the instrumental line shape function, the gain calibration error, and the spectral noise. The error contribution of interfering gases is almost negligible. The vertical resolution depends on altitude and atmospheric conditions. In 2002–2004 it varies between 2.5 km at the lowest altitudes and 6 km at 70 km, while in 2005–2012 it covers 2 to 5.5 km in the same altitude range. The horizontal smearing in terms of the full width at half maximum of the horizontal component of the two-dimensional averaging kernel matrix is smaller than, or approximately equal to, the distance between two subsequent limb scans at all altitudes. This implies that the horizontal resolution is sampling-limited or optimal, respectively. An additional data version is made available that is free of the formal a priori information and thus more user-friendly for certain applications. Version 8 ozone results show a better consistency between the two MIPAS measurement periods. They seem to be more realistic than preceding data versions in terms of long-term stability, as at least a part of the drift is corrected. Further, the representation of elevated stratopause situations is improved. © Author(s) 2023., This study was partly funded by the Deutsches Zentrum für Luft- und Raumfahrt (DLR) (SEREMISA; contract no. 50EE1547). The IAA team was supported by the Ministerio de Ciencia, Innovación y Universidades (MCIU) (project no. PID2019-110689RB-100/AEI/10.13039/501100011033)., With funding from the Spanish government through the "Severo Ochoa Centre of Excellence" accreditation (CEX2021-001131-S).

We present CO density profiles up to about 100 km in the Martian atmosphere obtained for the first time from retrievals of solar occultation measurements by the Nadir and Occultation for Mars Discovery (NOMAD) onboard ExoMars Trace Gas Orbiter (TGO). CO is an important trace gas on Mars, as it is controlled by CO2 photolysis, chemical reaction with the OH radicals, and the global dynamics. However, the measurements of CO vertical profiles have been elusive until the arrival of TGO. We show how the NOMAD CO variations describe very well the Mars general circulation. We observe a depletion of CO in the upper troposphere and mesosphere during the peak period, LS = 190°–200°, more pronounced over the northern latitudes, confirming a similar result recently reported by Atmospheric Chemistry Suite onboard TGO. However, in the lower troposphere around 20 km, and at least at high latitudes of the S. hemisphere, NOMAD CO mixing ratios increase over 1,500 ppmv during the GDS (Global Dust Storm) onset. This might be related to the downwelling branch of the Hadley circulation. A subsequent increase in tropospheric CO is observed during the decay phase of the GDS around LS = 210°–250° when the dust loading is still high. This could be associated with a reduction in the amount of OH radicals in the lower atmosphere due to lack of solar insolation. Once the GDS is over, CO steadily decreases globally during the southern summer season. A couple of distinct CO patterns associated with the Summer solstice and equinox circulation are reported and discussed. © 2023. American Geophysical Union. All Rights Reserved., The IAA/CSIC team acknowledges financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa” award for the Instituto de Astrofisica de Andalucia (SEV-2017-0709) and funding by Grant PGC2018-101836-B-100 (MCIU/AEI/FEDER, EU). F.G.G. is funded by the Spanish Ministerio de Ciencia, Innovación y Universidades, the Agencia Estatal de Investigación and EC FEDER funds under project RTI2018-100920-J-I00 and from Grant CEX2021-001131-S funded by MCIN/AEI/https://doi.org/10.13039/501100011033. ExoMars is a space mission of the European Space Agency (ESA) and Roscosmos. The NOMAD experiment is led by the Royal Belgian Institute for Space Aeronomy (IASB-BIRA), assisted by Co-PI teams from Spain (IAA-CSIC), Italy (INAF-IAPS), and the United Kingdom (Open University). This project acknowledges funding by the Belgian Science Policy Office (BELSPO), with the financial and contractual coordination by the ESA Prodex Office (PEA 4000103401, 4000121493) as well as by UK Space Agency through Grants ST/V002295/1, ST/V005332/1 and ST/S00145X/1 and Italian Space Agency through Grant 2018-2-HH.0. US investigators were supported by the National Aeronautics and Space Administration.

New global nitric oxide (NO) volume mixing ratio and lower-thermospheric temperature data products, retrieved from Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) spectra with the Institute of Meteorology and Climate Research and Instituto de Astrofísica de Andalucía (IMK-IAA) MIPAS data processor, have been released. The dataset covers the entire Envisat mission lifetime and includes retrieval results from all MIPAS observation modes. The data are based on European Space Agency (ESA) version 8 calibration and were processed using an improved retrieval approach compared to previous versions, specifically regarding the choice and construction of the a priori and atmospheric parameter profiles, the treatment of horizontal inhomogeneities, the treatment of the radiance offset correction, and the selection of optimized numerical settings. NO retrieval errors in individual observations are dominated by measurement noise and range from 5 % to 50 % in the stratosphere and thermosphere and reach 40 % to 90 % in the mesosphere. Systematic errors are typically within 10 %–30 %. Lower-thermospheric temperature errors are 5 to 50 K with a systematic component of around 20 K, the latter being dominated by non-thermodynamic equilibrium (non-LTE)-related uncertainties. NO data from different observation modes are consistent within 5 %–10 %. MIPAS version 8 temperatures have a better representation of the diurnal tide in the lower thermosphere compared to previous data versions. The new MIPAS temperatures are systematically warmer than results from the empirical US Naval Research Laboratory Mass Spectrometer Incoherent Scatter Radar (NRLMSIS) version 2.0 model by 30 to 80 K in the 100–120 km region and are colder above.

The Changing-Atmosphere Infra-Red Tomography Explorer (CAIRT) is one of the four candidates for ESA’s Earth Explorer 11. This mission has been proposed in order to achieve a step change in our understanding of the coupling of atmospheric circulation, composition and climate. The CAIRT concept proposes to perform limb tomography of the atmosphere from the troposphere to the lower thermosphere (about 5 to 115 km altitude) with a swath between 300 and 500 km and high spatial and spectral resolution to provide a three-dimensional picture of atmospheric structure at unprecedented scales. This contribution will investigate the capability of CAIRT to analyse stratosphere to troposphere exchange using an Observing System Simulation Experiment (OSSE). In this effort, a reference atmosphere – the nature run in the OSSE terminology – is built based on the Copernicus Atmosphere Monitoring Services (CAMS) control run (i.e. with a horizontal resolution ~40 km and a vertical resolution ~500 m in the tropopause region). The nature run is used to generate CAIRT ozone profiles, along with a CAIRT orbit simulator and a simulator to generate CAIRT ozone retrieval responses and error covariance matrix. Simulated CAIRT ozone profiles are then assimilated by the Belgian Assimilation System for Chemical ObsErvations (BASCOE) to provide ozone analyses – the assimilation run. In order to measure the added value of CAIRT data in the assimilation run, a BASCOE control run without CAIRT assimilation, is also done. Ozone fluxes across the tropopause are calculated from three numerical experiments which will be discussed in this presentation., The 28th IUGG General Assembly (IUGG2023) (Berlin 2023)

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited., This paper describes the error estimation for temperature and trace gas mixing ratios retrieved from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) limb emission spectra. The following error sources are taken into account: measurement noise, propagated temperature and pointing noise, uncertainties in the abundances of spectrally interfering species, instrument line shape errors, and spectroscopic data uncertainties in terms of line intensities and broadening coefficients. Furthermore, both the direct impact of volatile and persistent gain calibration uncertainties, offset calibration, and spectral calibration uncertainties, as well as their impact through propagated calibration-related temperature and pointing uncertainties, are considered. An error source specific to the MIPAS upper atmospheric observation mode is the propagation of the smoothing error crosstalk of the combined NO and temperature retrieval. Whenever non-local thermodynamic equilibrium modelling is used in the retrieval, related kinetic constants and mixing ratios of species involved in the modelling of populations of excitational states also contribute to the error budget. Both generalized Gaussian error propagation and perturbation studies are used to estimate the error components. Error correlations are taken into account. Estimated uncertainties are provided for a multitude of atmospheric conditions. Some error sources were found to contribute both to the random and the systematic component of the total estimated error. The sequential nature of the MIPAS retrievals gives rise to entangled errors. These are caused by error sources that affect the uncertainty in the final data product via multiple pathways, i.e., on the one hand, directly, and, on the other hand, via errors caused in a preceding retrieval step. These errors tend to partly compensate for each other. The hard-to-quantify effect of the horizontally non-homogeneous atmosphere and unknown error correlations of spectroscopic data are considered to be the major limitations of the MIPAS error estimation. © Author(s) 2022., This research has been supported by the Agencia Estatal de Investigación (grant no. PID2019-110689RB-I00). The article processing charges for this open-access publication were covered by the Karlsruhe Institute of Technology (KIT)., With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.

A new global O3 data product retrieved from Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) spectra with the IMK/IAA MIPAS data processor has been released. These data are based on ESA version 8 recalibration of radiance spectra which takes detector aging into consideration to minimize drifts. The new ozone retrievals use improved temperatures and thus suffer less from the propagation of related errors. Changes in the level-2 processing with respect to previous data versions and relevant to ozone include: (1) The background continuum is now considered up to 58 km. (2) A priori information is now used to constrain the retrieval of the radiance offset. (3) Water vapour is jointly retrieved along with ozone mixing ratios. (4) A more adequate regularization has been chosen. (5) Ozone lines in the MIPAS A band (685–980 cm-1) are used almost exclusively because of inconsistencies in spectroscopic data of the MIPAS AB band (1010–1180 cm-1). Only at altitudes above 50 km, where A band ozone lines do not provide sufficient information, ozone lines in the MIPAS AB band are used. (6) Temperature-adjusted climatologies of vibrational temperatures of O3 and CO2 are considered to account for non-local thermodynamic equilibrium radiation. Ozone errors are estimated to be less than 10 % in the altitude range 20–50 km. The error budget is dominated by the spectroscopic errors of ozone and carbon dioxide. The latter error contribution is propagated from the results of temperature and line-of-sight retrievals. Further notable contributions are the uncertainty of the instrumental line shape function, the gain calibration error, and the spectral noise, directly in the ozone lines and propagated via the previously retrieved temperature and line-of-sight. The error contribution of interfering gases is almost negligible. The vertical resolution in terms of the full width at half maximum of the averaging kernel rows depends on altitude and atmospheric conditions. For the measurement period 2002–2004 it varies between 2.5 km at the lowest altitudes and 6 km at 70 km, while in 2005–2012 it covers 2 to 5.5 km in the same altitude range. The horizontal smearing in terms of the full width at half maximum of the horizontal component of the 2-dimensional averaging kernel matrix is smaller than, or approximately equal to, the distance between two subsequent limb scans, at all altitudes. This implies that the horizontal resolution is sampling-limited or optimal, respectively. Along with the regular representation of the data, that have non-unity averaging kernels, a resampled data version is made available that is free of formal a priori information and thus more user-friendly for certain applications. Version 8 ozone results show a better consistency between the two MIPAS measurement periods. They seem to be more realistic than preceding data versions in terms of long-term stability, as at least a part of the drift is corrected. Further, the representation of elevated stratopause situations is improved, but there is still some indication of a positive bias in the upper stratosphere.

Introduction: CO is one of the important trace gas species in the Martian atmosphere which is linked to the Martian photochemistry through its production in the upper atmosphere in the photolysis of CO2 and its destruction in the lower altitudes in a chemical reaction with OH radicals. Thus it can be used as a proxy to study the HOx chemistry. CO is also one of the long-lived species in the atmosphere and its global distribution is controlled by the atmospheric dynamics. The observations made by the Solar Occultation (SO) spectrometer onboard TGO ExoMars space-craft presents with opportunity for systematic mapping of CO density profiles in the atmosphere for the first time.Retrieval Methodology: SO is one of the spectrometers in the NOMAD suite onboard Exo Mars Trace Gas Orbiter designed for the observations of the trace species active in the spectral range 2.3 – 4.3 μm [2]. The spectrometer is built using diffraction grating in Littrow configuration. It uses Acousto Optical Tunable Filter (AOTF) to select one wavelength range corresponding to a single diffraction order. The selected order passes through a set of parabolic mirrors before getting incident on the grating. The diffracted light is then guided through the same mirrors to the detector of the spectrometer. The spectrometer is operated usually to record diffraction orders from 110 to 191, but in regular operations, up to six different diffraction orders can be selected. In this wide range of diffraction orders, CO sounding is suitable only in the diffraction orders 186 – 191 where the CO absorption lines are strong and well separated from each other.The diffraction orders 186 – 191, however, are not measured simultaneously. Orders 186, 189, and 190 are the most commonly used so far, and therefore, a better geographical coverage was obtained from them compared to the other orders. Our aim is to obtain a similar retrieval performance for these orders using the state-of-the art retrieval method developed at IAA/CSIC. The transmission spectra for every order suffer from residual calibration effects like spectral shift and bending which are corrected using a cleaning methodology described in [3,4]. We use line-by-line radiative transfer model KOPRA (Karlsruhe Optimized and Precise Radiative transfer Algorithm)[5] as a forward model, which was adapted for Mars and to the NOMAD instrument characteristics, in conjunction with an interactive solver (RCP) to retrieve CO from the cleaned spectra [6]. This follows a similar work for the diffraction order 190 and is applied to the first year of TGO observation [1]. Acknowledgement: The IAA/CSIC team acknowledges financial support from the State Agency for Research of the Spanish MCIU through the ‘Center of Excellence Severo Ochoa’ award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709). MALV was funded by grant PGC2018-101836-B-100 (MCIU/AEI/FEDER, EU). ExoMars is a space mission of the European Space Agency (ESA) and Roscosmos. The NOMAD experiment is led by the Royal Belgian Institute for Space Aeronomy (IASB-BIRA), assisted by Co-PI teams from Spain (IAA-CSIC), Italy (INAF-IAPS), and the United Kingdom (Open University). US investigators were supported by the National Aeronautics and Space Administration. References[1]A. Modak, et al. Retrieval of martian atmospheric CO vertical profiles from the first year of NOMAD/TGO solar occultation observations. JGR-submitted , 2022.[2]A. C. Vandaele, et al. NOMAD, an integrated suite of three spectrometers for the exoMars trace gas mission: Technical description, science objectives and expected performance. Space Science Reviews , 214(5):1–47, 2018.[3]M.-A. López-Valverde, et al, Martian atmospheric temperature and density profiles during the 1st year of NOMAD/TGO solar occultation measurements. JGR-submitted , 2022.[4]A. Brines, et al. Water vapor vertical distribution on Mars during the perihelion season of MY34 and MY35 from ExoMars TGO/NOMAD solar occultation measurements. JGR-submitted, 2022.[5]Stiller, G. P. The Karlsruhe Optimized and Precise Radiative transfer Algorithm (KOPRA), 2000.[6]Á. A. Jurado Navarro et al. Retrieval of CO2 and collisional parameters from the mipas spectra in the earth atmosphere. 2016.

The Martian mesosphere, and in particular the upper mesosphere, above about 80 km from the surface, remains poorly explored in comparison with the troposphere and the thermosphere/ionosphere. Observations by the NOMAD and ACS instruments on board the ExoMars Trace Gas Orbiter mission (TGO in what follows) are starting to fill this gap by providing measurements such as the abundance of mesospheric water and the effects of global dust storms (Vandaele et al., 2019; Belyaev et al., 2021; Brines et al., 2022), the CO variability (Modak et al., 2022) or the temperature and density structure (López-Valverde et al., 2022). For the first time we have a set of diverse atmospheric parameters derived simultaneously with good vertical resolution and from a single instrument, which is ideal for model validation purposes.In this work, we will compare the predictions of the LMD-Mars GCM (LMD-MGCM) in the mesosphere with the NOMAD results (abundances of CO2, CO, and H2O, as well as temperature) obtained by the retrieval scheme developed at the Instituto de Astrofisica de Andalucia-CSIC (IAA), in order to validate the model and to gain insight into the physical processes at the origin of the observed structures. In particular, we will focus on the comparison of the CO2 density and temperature structure observed below ~120 km (López-Valverde et al., 2022) during the second half of Mars Year 34, a period including the MY34 global dust storm. We will show that the model reproduces well the strong seasonal variations of the CO2 density observed by NOMAD. However, the model tends to overestimate the temperatures above ~50 km.AcknowledgmentsF.G-G. is funded by the Spanish Ministerio de Ciencia, Innovación y Universidades, the Agencia Estatal de Investigación and EC FEDER funds under project RTI2018-100920-J-I00. MALV, AB, AM, and AS were supported by grant PGC2018-101836-B-100 (MCIU/AEI/FEDER, EU). The IAA team acknowledges financial support from the State Agency for Research of the Spanish MCIU through the “Center of Excellence Severo Ochoa" award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709)

NOMAD [1] (Nadir and Occultation for MArs Discovery) is a multi-channel spectrometer onboard the ExoMars 2016 Trace Gas Orbiter (TGO), which began its observations in April 2018. The Solar Occultation (SO) channel has a spectral range coverage from 2.3 to 4.3 μm (2320 to 4350 cm-1), where numerous ro-vibrational bands of H2O are located. An Acousto-Optical Tunable Filter (AOTF) is used to select different spectral windows (with a typical width from 20 to 35 cm-1) corresponding to the desired diffraction orders to be used during an atmospheric scan. The SO channel has a sample rate of ∼1 s, that allows a vertical sampling of typically 1 km. In order to obtain as much information as possible from the Martian atmosphere, for this study we have analyzed data from diffraction orders 134 (3011-3035 cm-1), 136 (3056-3081 cm-1), 168 (3775-3805 cm-1) and 169 (3798-3828 cm-1), taken during different solar occultation scans since the beginning of the science operations phase of the TGO/ExoMars mission. This combination of diffraction orders allowed us to obtain an optimal mapping of the distribution of the water vapor at altitudes from ∼10 km up to about ∼100 km and in different atmospheric conditions, and hence, permitting the study of its spatial and seasonal variability.The data presented here have been analyzed with pre-processing and cleaning tools developed entirely at the IAA (see companion contributions to this conference [2-4]), and then, inverted using a state-of-the-art retrieval scheme [5]. For the inversion, we have introduced a novel strategy of combining (when coincident in the same solar occultation) pairs of NOMAD orders (in contrast to a post-processing strategy), using orders 134 or 136 for the lower atmosphere, commonly below 60 km, and orders 168 or 169 for the upper atmosphere. This combination procedure allows us to exclude heavily saturated absorption lines present at low altitudes in orders 168-169, which contain strong absorption lines, permitting the exploitation of these orders for the analysis of the atmosphere up to 100 km. Here we present and discuss detailed maps showing the vertical distribution of the water vapor abundance of a subset of the solar occultations observed during the first two years of TGO/ExoMars. This research confirms some findings also obtained by other teams within the NOMAD consortium [6-8] and ACS instrument [9], showing that dust storms allow water vapor to reach higher altitudes in the atmosphere. This is important for the escape of atomic hydrogen [10] and therefore, for the long-term evolution of the Martian atmosphere. Detailed studies on the characterization of the Martian hygropause and saturation events are also presented. AcknowledgmentsThe IAA/CSIC team acknowledges financial support from the State Agency for Research of the Spanish MCIU through the 'Center of Excellence Severo Ochoa' award for the Instituto de Astrofísica de Andalucía (SEV- 2017-0709) and funding by grant PGC2018-101836-B-100 (MCIU/AEI/FEDER, EU). ExoMars is a space mission of the European Space Agency (ESA) and Roscosmos. The NOMAD experiment is led by the Royal Belgian Institute for Space Aeronomy (IASB-BIRA), assisted by Co-PI teams from Spain (IAA-CSIC), Italy (INAF-IAPS), and the United Kingdom (Open University). US investigators were supported by the National Aeronautics and Space Administration. References1. Vandaele, A. C. et al. NOMAD, an integrated suite of three spectrometers for the ExoMars Trace Gas mission: technical description, science objectives and expected performance. Space Science Reviews 214, 1-47 (2018).2. López-Valverde, M. A. et al. Temperature and density profiles from the two solar occultation instruments NOMAD and ACS during a full Martian Year. EPSC (2022).3. Modak, A. et al. Mapping of Martian CO from NOMAD solar occultation measurements for MY35 and 36. EPSC (2022).4. Stolzenbach, A. et al. Composition and size of Martian aerosols as seen in the IR by NOMAD-SO experiment onboard TGO. EPSC (2022).5. Jurado Navarro, A. A. et al. Retrieval of CO2 and collisional parameters from the MIPAS spectra in the earth atmosphere (2016).6. Aoki, S et al. Water vapor vertical profiles on Mars in dust storms observed by TGO/NOMAD. Journal of Geophysical Research: Planets (2019).7. Aoki, S. et al. Global vertical distribution of water vapor on Mars: Results from 3.5 years of ExoMarsTGO/NOMAD science operations. submitted (2022).8. Villanueva, G. L. et al. Water heavily fractionated as it ascends on Mars as revealed by ExoMars/NOMAD. Science Advances 7, eabc8843 (2021).9. Fedorova, A. A. et al. Stormy water on Mars: The distribution and saturation of atmospheric water during the dusty season. Science 367, 297-300 (2020).10. Chaffin, M., Deighan, J, Schneider, N. & Stewart, A. Elevated atmospheric escape of atomic hydrogen from Mars induced by high-altitude water. Nature geoscience 10, 174-178 (2017).

One of the goals of the ESA and Roscosmos Exomars Trace Gas Orbiter (TGO) is the exploitation of the two solar occultation instruments NOMAD [1] and ACS [2] to characterize the thermal structure of the Martian atmosphere with unprecendented vertical resolution, and from the ground up to the thermosphere. Specifically for the upper atmosphere this is a unique opportunity [3] and we present here an on-going effort to retrieve CO2 abundance and temperature profiles simultaneously from each of these instruments and to combine them for a mutual validation and for obtaining a most complete mapping from the TGO orbit. We developed a retrieval suite common for both instruments, comprising: (a) a cleaning/pre-processing module to build vertical profiles of calibrated transmittances which computes and correct for residual calibration and instrumental effects like spectral shifts, bending of the continuum and variations in the instrument line shape; (b) a state-of-the-art retrieval scheme designed originally for Earth atmospheric remote sensing [4,5,6] and applied to Mars [7], in order to derive simultaneous density and temperature profiles allowing for hydrostatic adjustments during the internal iteration.Recently the first application of this retrieval scheme focused on measurements by the NOMAD SO channel at altitudes below 100 km, and for the first year of TGO operations, from April 2018 to March 2019 (second half or “perihelion” season of MY34), and revealed very interesting results [8]. The thermal structure is strongly affected by the MY34 global dust storm at all altitudes, a cold mesosphere (in comparison to global climate models) was found during the post-GDS period, and wavy structures at mesospheric altitudes in the morning terminator seem to reveal very strong thermal tides at low-mid latitudes.In this presentation we also focus on the Martian troposphere and mesosphere and build upon the above mentioned work during the 1st year of TGO by extending the study to a full Mars year and adding retrievals from ACS MIR channel. Both NOMAD/SO and ACS/MIR channels observe the strong CO2 ro-vibrational band at 2.7 micron in the same spectral region with some differences in spectral resolution and noise level, in addition to very differnet instrument characteristics, which are included in our retrieval approach. In obth cases we use calibrated atmospheric transmittances to tackle three targets, CO2 density, temperature, and dust loading, in a simultaneous global-fit inversion, including contaminant species like H2O. The contamination by aerosol can severely limit the ability to sound low tangent altitudes with both instruments, when the gas absorption lines become hidden within the aerosol continuum. But also these measurements permit a good characterization of aerosol properties [9]. Propagation of measurement noise, tunning of regularization, and computation of averaging kernels are performed with the same code and the comparison of the retrieval performance is a first step towards a common validation between these two instruments, considering that a complete correlation is not possible since the two instruments' individual solar occulation scans are non-coincident in time and space. Our results will be discussed and compared to paralell retrieval efforts by other teams within the NOMAD and ACS consortia using the same datasets [10, 11, 12]. We will also compare them with specific runs of the LMD-Mars GCM (see also a companion presentation in this conference on this specific topic [13]). One of the important applications of our inversion is to supply true-field and a.priori inputs for the inversion of trace species from collocated NOMAD spectra, as we are doing for water vapour [14] and carbon monoxide [15]. AcknowledgmentsThe IAA/CSIC team acknowledges financial support from the State Agency for Research of the Spanish MCIU through the ‘Center of Excellence Severo Ochoa’ award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709) and funding by grant PGC2018-101836-B-100 (MCIU/AEI/FEDER, EU). ExoMars is a space mission of the European Space Agency (ESA) and Roscosmos. The NOMAD experiment is led by the Royal Belgian Institute for Space Aeronomy (IASB-BIRA), assisted by Co-PI teams from Spain (IAA-CSIC), Italy (INAF-IAPS), and the United Kingdom (Open University). US investigators were supported by the National Aeronautics and Space Administration.References[1] Vandaele et al., Space Science Reviews 214, 5, 2018[2] Korablev et al., Space. Sci. Rev. 214, 7 (2018).[3] Lopez-Valverde et al., Space Sci Rev, 214, 29 (2018)[4] Funke, B., et al. , Atmos. Chem. Phys., 9(7), 2387–2411 (2009).[5] Stiller et al., JQSRT, 72, 249–280 (2002)[6] von Clarmann et al., J. Geophys. Res. 108, 4746 (2003)[7] Jimenez-Monferrer et al., Icarus, 353, 113830 (2020), doi.org/10.1016/j.icarus.2020.113830.[8] Lopez-Valverde et al., JGR-Planets (submitted, 2022)[9] Stolzenbach et al., JGR-Planets (submitted, 2022) and Stolzenbach et al., EPSC 2022 (this conference)[10] Trompet et al., JGR-Planets (submitted, 2022)[11] Belyaev et al., GRL[12] Belyaev et al., JGR-Planets (submitted, 2022)[13] Gonzalez-Galindo et al., EPSC 2022 (this conference)[14] Brines et al., JGR-Planets (submitted, 2022) and Brines et al., EPSC 2022 (this conference)[15] Modak et al., JGR-Planets (submitted, 2022) and Modak et al., EPSC 2022 (this conference)

IntroductionThe nature, size and content of aerosols in the atmosphere affect the energy budget on all planets, hence the atmospheric dynamic of the planet. Mars exhibits three types of atmospheric aerosol. Mineral dust, water ice and carbon dioxide ice. Martian aerosols nature and size distribution were observed using many different methods and experiments, from rovers to satellites. Exhaustive review scan be found in [1] and in [2]. Usually, dust effective radius, reff, ranges from 1 to 2 μm and its effective variance, νeff, from 0.2 to 0.4. H2O ice reff ranges from 1 to 5 μm and its νeff from 0.1 to 0.4. However, these two parameters and their variability are poorly constraint in the vertical to date. ExoMars TGO mission (ESA/Roscosmos) was primarily designed to study trace gases, thermal structure and aerosol content in Mars atmosphere with unprecedented vertical resolution [3]. NOMAD-SO Data processingNOMAD (Nadir and Occultation for MArs Discovery) is suite of two infrared spectrometers onboard the ExoMars 2016 Trace Gas Orbiter (TGO) orbiter, covering the spectral range of 0.2 to 4.3 μm [4]. An Acousto-Optical Tunable Filter (AOTF) is used to select different spectral windows. The sampling of this channel is approximately of 1 second, allowing a vertical sampling about 1km. the SO channel is able to observe the atmosphere at a given altitude with 6 different diffraction orders. For this study, we selected a configuration of 5 diffraction orders (121,134,149,168,190) effectively spanning the overall spectral range of NOMAD.In order to evaluate the local extinction due to aerosols, we use an inversion program called Retrieval Control Program (RCP). It is a multi-parameter non-linear least squares fitting of measured and modelled spectra [5]. Its forward model, KOPRA, was recently adapted to limb emissions on Mars [6] and for solar occultation data on Mars for the first time. RCP solves iteratively the inverse problem [7] and is described in details in [8]. The regularization matrix is build from Tikhonov-type terms of different orders which can be combined to obtain a custom-tailored regularization for any particular retrieval problem.An example of the retrieved extinction profile is shown in Fig 1. The retrieved extinctions differs from previous work on aerosols using ACS data [9,10] using the Onion-peeling or Abel's transform method since this global fit is less affected by the large error propagation to low altitudes typical of those methods, and the lower Martian atmosphere is precisely where aerosols are particular relevant.Fig 1.Mean extinction cross-section ratio modellingIn order to model the optical behavior of the Martian aerosol we chose the log-normal distribution which is widely used in atmospheric sciences. It is a function of two parameters (rg, σg). In optics, we change those parameters to more suitable ones, the effective radius, reff and its corresponding effective variance νeff. For any aerosol size distribution, the extinction k is km-1 is k(λ) = N . σext (λreff,νeff). N is the aerosol number density and σext (λ,reff,νeff) is the mean average extinction cross-section at a wavelength λ, a specific aerosol distribution defined by (reff,νeff). We build a look-up table of dust and water ice σext at the selected NOMAD order's wavelengths for different sets of (reff,νeff). The extinction are evaluated with a Lorenz-Mie code for polydisperse spherical particle from [11].Aerosol composition and size distribution evaluationWe will detail the process of evaluating the aerosol composition and size distribution that consists of a mix of non-linear least square and brute force in order to evaluate the best set of parameters (reff,νeff ,γ) where γ represent a mixture of dust and H2O ice. The NLSQ algorithm is provided by the SciPy Python package [12]. To assess the robustness and limitations of our evaluation procedure, we will present results against synthetic extinction signal. We will discuss our main results, especially for the period covering the Global Dust Storm of MY34 (Fig 2.).Fig 2.AcknowledgmentsThe IAA/CSIC team acknowledges financial support from the State Agency for Research of the Spanish MCIU through the \emph{"Center of Excellence Severo Ochoa"} award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709) and funding by grant PGC2018-101836-B-100 (MCIU/AEI/FEDER, EU). ExoMars is a space mission of the European Space Agency (ESA) and Roscosmos. The NOMAD experiment is led by the Royal Belgian Institute for Space Aeronomy (IASB-BIRA), assisted by Co-PI teams from Spain (IAA-CSIC), Italy (INAF-IAPS), and the United Kingdom (Open University).References[1] Robert M. Haberle et al., eds. The Atmosphere and Climate of Mars. Cambridge University Press, 2017.[2] R. Todd Clancy et al. “The distribution, composition, and particle properties of Mars meso-spheric aerosols: An analysis of CRISM visible/near-IR limb spectra with context from near-coincident MCS and MARCI observations”. Icarus 328 (2019).[3] J. Vago et al. “ESA ExoMars program: The next step in exploring Mars”. SSR 49.7 (2015).[4] A. C. Vandaele et al. “NOMAD, an Integrated Suite of Three Spectrometers for the ExoMarsTrace Gas Mission: Technical Description, Science Objectives and Expected Performance”. SSR 214.5 (2018).[5] T. von Clarmann et al. “Retrieval of temperature and tangent altitude pointing from limb emission spectra recorded from space by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS)”. JGR: Atmospheres 108.D23 (2003).[6] Sergio Jiménez-Monferrer et al. “CO2 retrievals in the Mars daylight thermosphere from its 4.3μm limb emission measured by OMEGA/MEx”. Icarus 353 (2021).[7] Clive D Rodgers. Inverse Methods for Atmospheric Sounding. WORLD SCIENTIFIC, 2000.[8] Jurado Navarro et al. Retrieval of CO2 and collisional parameters from the MIPAS spectra in the Earth atmosphere. Universidad de Granada, 2016.[9] M. Luginin et al. “Properties of Water Ice and Dust Particles in the Atmosphere of Mars During the 2018 Global Dust Storm as Inferred From the Atmospheric Chemistry Suite”. JGR: Planets 125.11 (2020).[10] A. Stcherbinine et al. “Martian Water Ice Clouds During the 2018 Global Dust Storm as Observed by the ACS-MIR Channel Onboard the Trace Gas Orbiter”. JGR: Planets 125.3 (2020).[11] Michael I Mishchenko et al. Scattering, absorption, and emission of light by small particles. Cambridge university press, 2002.[12] Pauli Virtanen et al. “SciPy 1.0: Fundamental Algorithms for Scientific Computing in Python”. Nature Methods 17 (2020).

Poster for the SEA 2022 meeting describing the comparison between ExoMars NOMAD solar occultation observations retrieved at the Instituto de Astrofísica de Andalucía and the predictions of a ground-to-exobase Global Climate Model. The temperature structure and the abundances of CO2, CO, and H2O in the mesosphere (up to ~100 km) are compared., This work was supported by the Spanish Ministry of Science and Innovation, the Agencia Estatal de Investigación, and by the UE FEDER funds under grants RTI2018-100920-J-I00 and PGC2018-101836-BI00. The IAA/CSIC team acknowledges financial support from the State Agency for Research of the Spanish MCIU through the 'Center of Excellence Severo Ochoa' award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709)

We investigate the impact of the so-called energetic particle precipitation (EPP) indirect effect on lower stratospheric ozone, ClO, and ClONO2 in the Antarctic springtime. We use observations from the Microwave Limb Sounder (MLS) and Ozone Monitoring Instrument (OMI) on Aura, the Atmospheric Chemistry Experiment – Fourier Transform Spectrometer (ACE-FTS) on SCISAT, and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat, covering the period from 2005 to 2017. Using the geomagnetic activity index Ap as a proxy for EPP, we find consistent ozone increases with elevated EPP during years with an easterly phase of the quasi-biennial oscillation (QBO) in both OMI and MLS observations. While these increases are the opposite of what has previously been reported at higher altitudes, the pattern in the MLS O3 follows the typical descent patterns of EPP-NOx. The ozone enhancements are also present in the OMI total O3 column observations. Analogous to the descent patterns found in O3, we also found consistent decreases in springtime MLS ClO following winters with elevated EPP. To verify if this is due to a previously proposed mechanism involving the conversion of ClO to the reservoir species ClONO2 in reaction with NO2, we used ClONO2 observations from ACE-FTS and MIPAS. As ClO and NO2 are both catalysts in ozone destruction, the conversion to ClONO2 would result in an ozone increase. We find a positive correlation between EPP and ClONO2 in the upper stratosphere in the early spring and in the lower stratosphere in late spring, providing the first observational evidence supporting the previously proposed mechanism relating to EPP-NOx modulating Clx-driven ozone loss. Our findings suggest that EPP has played an important role in modulating ozone depletion in the last 15 years. As chlorine loading in the polar stratosphere continues to decrease in the future, this buffering mechanism will become less effective, and catalytic ozone destruction by EPP-NOx will likely become a major contributor to Antarctic ozone loss.

Retrieving global observations of gravity waves (GWs) from recent satellite missions is challenging. Nadir viewing satellites such as AIRS provide directional momentum fluxes, but lack fine vertical resolution and hence observe only those GWs with exceptionally high intrinsic phase speed. Limb scanning instruments such as HIRDLS and SABER have only a single measurement track and hence provide only an estimate of absolute GW momentum flux. In addition, the sparse along-track sampling of these limb sounders introduce uncertainties in horizontal wavelength. GPS-RO can provide GW profile triplets, allowing in principle the horizontal direction of GW propagation to be inferred, but these triplets are rare. Finally, direct wind measurements from Aeolus are restricted in altitude to less than ~25km and only provide the wind component in the direction of the lidar beam from one observational track. In consequence, also Aeolus cannot reveal horizontal propagation direction and GW momentum flux.This situation could be dramatically improved by bringing a limb imager into space. A limb imager combines the very dense spatial sampling of a nadir viewing instrument with the high vertical resolution of a limb sounder. This will provide an almost complete description of the vertical spectrum of GWs, necessary for inferring drag estimates. Such global GW momentum flux data would for the first time allow to retrieve a global momentum budget from the mid-troposphere to the upper mesosphere.The Changing-Atmosphere Infra-Red Tomography (CAIRT) mission candidate for ESA's Earth Explorer 11 proposes a limb imager for spatial sampling of 25 km across-track, 50 km along-track and 1 km in the vertical. From this we expect to infer directional GW momentum fluxes from the tropopause to 70 km or higher. This will allow longstanding scientific questions to be addressed such as the quantification of tropospheric GW sources and their related phase speed spectra and the identification of secondary wave generation in the stratosphere and lower mesosphere. Considering the momentum flux at higher altitudes, secondary wave generation competes with oblique GW propagation which allows GWs from low latitude sources to reach the high latitudes mesosphere and thus avoid critical levels. In general, two-way interaction with the background flow will be considered via the modulation of the GW spectrum by the winds and the mean wind accelerations by the GWs. In this contribution we will outline the CAIRT instrument concept, giving an overview of the mission’s objectives and demonstrate its potential using simulated observations.

Methane has a driving role in establishing the thermal structure of Jupiter's upper atmosphere. Hence, to know its spatial distribution, both in altitude and latitude, is essential for understanding that atmospheric region.The abundance of CH4 in Jupiter's upper atmosphere has been (or will soon be) derived using a number of different methods, e.g., solar occultation, the measurements of He and Ly-alpha airglow, and from the observations of near-IR emission near 3.3 µm (ISO/SWS, JUNO/JIRAM so far and, in the near future, from JWST/NIRSpec). The retrieved values derived from these techniques show rather different values, particularly around the homopause. Even different studies of the same ISO/SWS spectral radiance yield very different CH4 volume mixing ratio profiles.Here, we will discuss the important role and the adequate use of the collisional relaxation of the CH4 high-energy levels when deriving CH4 abundances near the mesopause from NIR emission radiances. Further, we will also show some results on the important role of spectrocopic data of the CH4 3.3 µm hot bands for those analyses. Those studies will be presented for the particular case of the ISO/SWS measurements, although they are equally applicable to other measurement sets such as those of JUNO/JIRAM and JWST/NIRSpec.

Ariel, the Atmospheric Remote-sensing Infrared Exoplanet Large-survey, was adopted as the fourth medium-class mission in ESA's Cosmic Vision programme to be launched in 2029. During its 4-year mission, Ariel will study what exoplanets are made of, how they formed and how they evolve, by surveying a diverse sample of about 1000 extrasolar planets, simultaneously in visible and infrared wavelengths. It is the first mission dedicated to measuring the chemical composition and thermal structures of hundreds of transiting exoplanets, enabling planetary science far beyond the boundaries of the Solar System. The payload consists of an off-axis Cassegrain telescope (primary mirror 1100 mm x 730 mm ellipse) and two separate instruments (FGS and AIRS) covering simultaneously 0.5-7.8 micron spectral range. The satellite is best placed into an L2 orbit to maximise the thermal stability and the field of regard. The payload module is passively cooled via a series of V-Groove radiators; the detectors for the AIRS are the only items that require active cooling via an active Ne JT cooler. The Ariel payload is developed by a consortium of more than 50 institutes from 16 ESA countries, which include the UK, France, Italy, Belgium, Poland, Spain, Austria, Denmark, Ireland, Portugal, Czech Republic, Hungary, the Netherlands, Sweden, Norway, Estonia, and a NASA contribution., Comment: Ariel Definition Study Report, 147 pages. Reviewed by ESA Science Advisory Structure in November 2020. Original document available at: https://www.cosmos.esa.int/documents/1783156/3267291/Ariel_RedBook_Nov2020.pdf/

While knowledge of the energy inputs from the Sun (as it is the primary energy source) is important for understanding the solar-terrestrial system, of equal importance is the manner in which the terrestrial part of the system organizes itself in a quasi-equilibrium state to accommodate and re-emit this energy. The ROSMIC project (2014–2018 inclusive) was the component of SCOSTEP’s Variability of the Sun and Its Terrestrial Impact (VarSITI) program which supported research into the terrestrial component of this system. The four themes supported under ROSMIC are solar influence on climate, coupling by dynamics, trends in the mesosphere lower thermosphere, and trends and solar influence in the thermosphere. Over the course of the VarSITI program, scientific advances were made in all four themes. This included improvements in understanding (1) the transport of photochemically produced species from the thermosphere into the lower atmosphere; (2) the manner in which waves produced in the lower atmosphere propagate upward and influence the winds, dynamical variability, and transport of constituents in the mesosphere, ionosphere, and thermosphere; (3) the character of the long-term trends in the mesosphere and lower thermosphere; and (4) the trends and structural changes taking place in the thermosphere. This paper reviews the progress made in these four areas over the past 5 years and summarizes the anticipated research directions in these areas in the future. It also provides a physical context of the elements which maintain the structure of the terrestrial component of this system. The effects that changes to the atmosphere (such as those currently occurring as a result of anthropogenic influences) as well as plausible variations in solar activity may have on the solar terrestrial system need to be understood to support and guide future human activities on Earth. [Figure not available: see fulltext.][Figure not available: see fulltext.][Figure not available: see fulltext.] © 2021, The Author(s)., WW and AS gratefully acknowledge funding from the ISEE (Institute for Space-Earth Environmental Research), Nagoya University, for support to attend the VarSITI summarizing workshop where the results discussed in this review paper were presented. With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.

Energetic particle precipitation leads to ionization in the Earth's atmosphere, initiating the formation of active chemical species which destroy ozone and have the potential to impact atmospheric composition and dynamics down to the troposphere. We report on one exceptionally strong high-energy electron precipitation event detected by balloon measurements in middle latitudes on 14 December 2009 with ionization rates locally comparable to strong solar proton events. This electron precipitation was likely caused by wave-particle interactions in the slot region between the inner and outer radiation belts, connected with still not well understood natural phenomena in the magnetosphere. Satellite observations of odd nitrogen and nitric acid are consistent with wide-spread electron precipitation into magnetic midlatitudes. Simulations with a 3D chemistry-climate model indicate almost complete destruction of ozone in the upper mesosphere over the region where high-energy electron precipitation occurred. Such an extraordinary type of energetic particle precipitation can have major implications for the atmosphere, and their frequency and strength should be carefully studied.

*Corresponding author: ashim@iaa.es Abstract NOMAD (Nadir and Occultation for Mars Discovery instrument), is a spectrometer suite onboard Exo Mars Trace Gas Orbiter having within its main scientific objectives the observations of the trace gases in the Martian atmosphere [1]. Here we focus on the retrieval of carbon monoxide (CO) vertical profiles with high vertical resolution. CO is an important trace species which acts as both photochemical and dynamical tracers. We retrieve CO from the solar occultation (SO) observation of the NOMAD orders (186 – 191) using a state-of-the-art retrieval method [2]. The observational dataset covers a wide range of latitudes and seasons. This permits us to study the impact of different conditions such as dust-storm seasons (local and global), southern summer and winter on the CO vertical profiles over different regions. Introduction CO is originated in the upper Martian atmosphere by the photolysis of CO2 and destroyed by the hydroxyl (OH) radicals in the lower atmosphere. Hydroxyl radicals thus recycle CO into CO2 [3]. The study of the CO vertical distribution is important to understand the photo-chemical stability of the atmosphere. CO not only links the chemistry of the carbon and odd hydrogen chemical families but is a long-lived species which also serves as a dynamical tracer. By far the current knowledge of CO vertical profiles is largely unconstrained due to lack of systematic measurements. Though the column density of CO has been measured by instruments like CRISM [4] (Compact Reconnaissance Imaging Spectrometer for Mars) for a wide range of latitudes and seasons for multiple Martian years, the lack of its regular mapping in the vertical, limits a full understanding of its distribution and variability. Very recently, CO density profiles were reported from ACS (Atmospheric Chemistry Suite) observations [5] which found a significant depletion in CO mixing ratio during the 2018 global dust storm. NOMAD is performing routine solar occultation measurements since April 2018. Our aim here is to retrieve CO vertical profiles from these measurements with the best achievable precision and resolution and to investigate its distribution and variability through the different seasons and latitudes. Retrieval of CO from NOMAD SO orders 186 – 190 We present vertical profiles of CO retrieved from a subset of NOMAD solar occultations. The SO channel of NOMAD operates in the 2.3 – 4.3 μm [3] where strong absorption lines for CO lie. In particular, the diffraction orders 186 (4180.32 cm-1 - 4213.88 cm-1) - 191 (4292.69 cm-1 - 4327.16 cm-1) allow for a good quality CO retrieval from 10 to about 100 km tangent altitudes. However, the recorded spectra suffer from calibration issues [6] such as bending and spectral shifts, in addition to variable systematic and random noise components. At IAA we have developed a cleaning procedure which correct the spectra for possible bending and spectral shift and makes it usable for a precise inversion of CO densities. We use the line-by-line radiative transfer model KOPRA (Karlsruhe Optimized and Precise Radiative transfer Algorithm) [2] as forward model, which was adapted to Mars and to the NOMAD instrument characteristics, in conjunction with an interactive solver (RCP) to retrieve CO from the cleaned spectra. Here we present a summary of this on-going work, which builds on a chain of retrievals of atmospheric aerosols, temperatures and density profiles derived from the same NOMAD scan but different diffraction orders, to obtain vertical profiles of CO in a consistent manner. We will also present first comparisons with Mars GCM results. Acknowledgement The IAA/CSIC team acknowledges financial support from the State Agency for Research of the Spanish MCIU through the ‘Center of Excellence Severo Ochoa’ award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709). MALV was funded by grant PGC2018-101836-B-100 (MCIU/AEI/FEDER, EU). ExoMars is a space mission of the European Space Agency (ESA) and Roscosmos. The NOMAD experiment is led by the Royal Belgian Institute for Space Aeronomy (IASB-BIRA), assisted by Co-PI teams from Spain (IAA-CSIC), Italy (INAF-IAPS), and the United Kingdom (Open University). US investigators were supported by the National Aeronautics and Space Administration. References [1] Neefs, Eddy, et al. "NOMAD spectrometer on the ExoMars trace gas orbiter mission: part 1—design, manufacturing and testing of the infrared channels."Applied optics 54.28 (2015): 8494-8520. [2] Jurado Navarro, Ángel Aythami. "Retrieval of CO2 and collisional parameters from the MIPAS spectra in the earth atmosphere." (2016). [3] McElroy, Michael B., and Thomas M. Donahue. "Stability of the Martian atmosphere."Science 177.4053 (1972): 986-988. [4] Smith, Michael D., et al. "The climatology of carbon monoxide and water vapor on Mars as observed by CRISM and modeled by the GEM-Mars general circulation model."Icarus 301 (2018): 117-131. [5] Olsen, K. S., et al. "The vertical structure of CO in the Martian atmosphere from the ExoMars Trace Gas Orbiter."Nature Geoscience14.2 (2021): 67-71. [6] Liuzzi, Giuliano, et al. "Methane on Mars: new insights into the sensitivity of CH4 with the NOMAD/ExoMars spectrometer through its first in-flight calibration." Icarus 321 (2019): 671-690.

1. The NOMAD-SO database and retrieval procedure The NOMAD-SO channel [1] is an infrared spectrometer onboard ExoMars TGO working in the 2.2 to 4.3 µm spectral range (2200-4500 cm-1). During a solar occultation measurement, NOMAD-SO scans six diffraction orders each second. These diffraction orders are recorded on four bins leading to a vertical sampling lower than one km. We use vertical profiles of calibrated transmittance and evaluated noise from level 1 data provided by the PI team. These level 1 scans are pre-processed by an in-house algorithm set up to clean the data of possible spectral shifts and/or bending. In order to retrieve the extinction vertical profile due to aerosol we use the model a state-of-the-art line by line radiative transfer forward model code called KOPRA, in conjunction with the iterative non-linear inversion scheme RCP, conceived and developed at the Institute of Meteorology and Climate Research (IMK) of Karlsruhe Institude for Technology and previously used in [2]. A priori and first guess profiles of the atmospheric thermal structure and composition, required by RCP, are taken from specific runs of the LMD Mars-GCM available through the MCD [3]. To minimize vertical error propagation we adopted a global fit inversion instead of a classical onion-peeling method. A first order Tikhonov regularization matrix is used for the aerosol extinction retrieval. For stability, RCP uses Levenberg-Marquardt damping method. Pre-processing and regularization parameters required fine-tuning, a task performed using a sample of orbits. We confirmed that these parameters are valid for all other scans. 2. Aerosols characterization and vertical profiles Aerosols in Martian atmosphere play a major role in several chemical and radative processes, affecting local to global dynamics and energy budget (see [4] for an exhaustive review of this subject). One crucial parameter is the aerosol composition and distribution, i.e the dust, water ice or CO2 ice content and its variation with with altitude, with a better vertical resolution than previous instruments. TGO offers an excellent opportunity to study it in detail for the first time because of its high vertical resolution. Using the vertical profile of aerosol extinction obtained from NOMAD-SO measurements as described above, we then apply a model/data fitting strategy of the aerosol extinction, as described in [5] in order to evaluate key parameters of the aerosol’s content in the martian atmosphere. We compare the retrieved aerosol extinction to a precomputed look-up table in the same spectral range from a Lorenz-Mie code to compute the scattering properties of an ensemble of polydisperse spherical particles [6] and using refractive indexes for martian dust, water ice and CO2 ice. This procedure allow us to evaluate two other key parameters besides the composition of aerosol present in the martian atmosphere, namely, the effective radius (reff) and the effective variance (νeff). These characteristic parameters of the aerosol’s distribution are of great interest constraining microphysics and dynamics. We will detail this procedure and compare the early results with available data for several chosen scans of NOMAD-SO observation during the first year of TGO operations, which include the GDS 34 [7]. Acknowledgements The IAA/CSIC team acknowledges financial support from the State Agency for Research of the Spanish MCIU through the "Center of Excellence Severo Ochoa" award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709) and funding by grant PGC2018-101836-B-100 (MCIU/AEI/FEDER, EU). ExoMars is a space mission of the European Space Agency (ESA) and Roscosmos. The NOMAD experiment is led by the Royal Belgian Institute for Space Aeronomy (IASB-BIRA), assisted by Co-PI teams from Spain (IAA-CSIC), Italy (INAF-IAPS), and the United Kingdom (Open University). US investigators were supported by the National Aeronautics and Space Administration. References [1] Vandaele, A.C., et al.: “Science objectives and performances of NOMAD, a spectrometer suite for the ExoMars TGO mission, Planet”. Space Sci., Vol. 119, pp 233-249, 2015. [2] A. A. Jurado-Navarro. “Retrieval of CO2 and collisional parameters from the MIPAS spectra in the Earth atmosphere”. PhD thesis, Universidad de Granada, 2015. [3] E. Millour, F. Forget, A. Spiga, M. Vals, V. Zakharov, L. Montabone, F. Lefèvre,F. Montmessin, J.-Y. Chaufray3 M. A. López-Valverde, F. González-Galindo, S. R.Lewis, P. L. Read, M.-C. Desjean, F. Cipriani and the MCD development team. “Mars climate database.” From Mars Express to ExoMars, 2018. [4] Kahre, M. A., Murphy, J. R., Newman, C. E., Wilson, R. J., Cantor, B. A., Lemmon, M. T., & Wolff, M. J. (2017). “The Mars dust cycle.” In R.M. Haberle (Ed.), The atmosphere and climate of Mars (pp. 229– 294). Cambridge: Cambridge University Press [5] Luginin, M., A. Fedorova, D. Belyaev, F. Montmessin, V. Wilquet, O. Korablev, J. -L. Bertaux, and A. C. Vandaele. “Aerosol Properties in the Upper Haze of Venus from SPICAV IR Data.” Icarus, 277. 2016. [6] Mishchenko, Michael I., Larry D. Travis, and Andrew A. Lacis. Scattering, absorption, and emission of light by small particles. Cambridge university press, 2002. [7] Liuzzi, G., Villanueva, G. L., Crismani, M. M. J., Smith, M. D., Mumma, M. J., Daerden, F., et al. . Strong variability of Martian water ice clouds during dust storms revealed from ExoMars Trace Gas Orbiter/NOMAD. Journal of Geophysical Research: Planets, 125, 2020.

Introduction NOMAD is a three-channel spectrometer on the ExoMars 2016 Trace Gas Orbiter. The NOMAD solar occultation (SO) channel has been operating around Mars since April 2018 [1]. In the past three years of science operations, we have performed many calibrations and have taken millions of spectra. This huge dataset allows us to continue to refine the calibration, through additional characterisation of the optical elements, detector performance and temperature-induced effects. SO channel By using an Acousto-Optic Tunable Filter (AOTF) in combination with an echelle grating spectrometer, the SO channel is able to operate at unprecedented spectral resolution – typically 0.15 to 0.25 cm-1 [2] – and is therefore able to measure trace gases and set stringent upper limits on the presence (or non-presence) of organic molecules in the Martian atmosphere [3]. In solar occultation mode, the Sun is used as the illumination source, meaning that very high Signal-to-Noise Ratios (SNRs) can be achieved, typically up to 2,000 for a single spectrum at the top of the atmosphere. The SO channel records 24 spectra per second in solar occultation mode, with a typical vertical sampling resolution (i.e. altitude difference between consecutive spectra) of around 50-150m [4]. Therefore, by binning multiple spectra together, the SNR can be increased significantly whilst still keeping a high vertical sampling resolution. Calibration However the AOTF-grating combination also presents additional challenges, as the optical properties of both elements must be independently characterised in order to correctly retrieve atmospheric gas concentrations. Analysis of the AOTF shape and sidelobes, and the Instrument Line Shape (ILS), are ongoing in several of the groups within the NOMAD team. Additional systematic effects have also been identified in the spectra e.g. [5] which hamper efforts to further increase SNR and thus reduce detection limits via binning. Whilst much calibration work on this has already been performed [2, 4], the calibration can still be improved and work is ongoing to understand these effects and how to remove them from the data. Applications Since the beginning of the mission, a particular emphasis has been placed on making observations of CH4 around Gale Crater, in both nadir and solar occultation modes. HCl detections observations are now also made regularly, following the discovery of HCl in the atmosphere [7, 8] and its isotopologue [5], which are close to the detection limit of the channel. Calibration improvements will allow us to further constrain the CH4 upper detection limit, observe lower concentrations of HCl, and further constrain the isotopic ratio. References [1] Vandaele, A. C. et al (2015) Planet. Space Sci., 119 ; [2] Liuzzi, G. et al. (2019) Icarus, 321 ; [3] Knutsen, E. W. et al. (2021), Icarus, 357 ; [4] Thomas, I. R. et al. (submitted 2021) “Calibration of NOMAD on ExoMars Trace Gas Orbiter: Part 1 – the SO channel”; [5] Liuzzi G. et al (2021) GRL 48(9); [6] Korablev, O. et al. (2021) Science Advances, 7(7); [8] Aoki, S. et al. (accepted 2021) “Annual appearance of hydrogen chloride on Mars and a striking similarity with the water vapor vertical distribution observed by TGO/NOMAD”, GRL.

CH4 plays a key role in the thermal structure of Jupiter's upper atmosphere and hence knowing its vertical distribution is crucial for its understanding. Methane concentrations have been inferred previously from the analyses of solar occultation, He and Ly-α airglow, and the ISO/SWS radiance measurements around 3.3 µm, showing all rather different values, particularly around the homopause. Even different analyses of the same ISO/SWS radiance spectra yield very different CH4 volume mixing ratio profiles. Here, we present a new analysis of the ISO/SWS radiance spectra by using a comprehensive non-Local Thermodynamic Equilibrium (non-LTE) model and the most recent collisional rates measured in the laboratory. Further, we briefly discuss the potential effects of non-LTE on CH4 3.3 µm emission of temperate Jupiter exoplanets.

Introduction Vertical profiles of CO2 and temperature with good vertical resolution are key measurements to characterize the Martian atmosphere, although difficult to obtain from remote observations [1]. For the first time these vertical profiles can be routinely obtained with a solar occultation technique by the instruments NOMAD and ACS on board the Exomars Trace Gas Orbiter [2,3]. A state-of-the-art retrieval scheme designed to derive atmospheric profiles of CO2 and temperature from the bottom to the top of the Martian atmosphere [4] is adapted to solar occulation and applied to exploit the operational sounding of these two instruments. The final goal of this on-going work is to characterize the Martian thermal structure from the troposphere up to the thermosphere with unprecedented vertical resolution and also to cross-validate both TGO instruments as best as possible, with a single retrieval code and entirely consistent data analysis approaches. Retrieval approach This work is focussed on the solar occultation channels NOMAD-SO and ACS-MIR, in routine operations since April 2018. To exploit these unique datasets, it is of paramount importance to examine the performance of the two instruments and to cross-validate their retrieval results as accurately as possible. For this purpose we apply a flexible and well tested Earth atmosphere retrieval scheme [5,6,7], to both of them, after adaptation to Mars atmospheric conditions [4] and the necessary accomodation of these channels characteristics [8]. The retrievals use calibrated transmittance spectra to tackle three targets, CO2 density, temperature, and dust loading, in a simultaneous global-fit inversion, with updated hydrostatic equilibrium in every iteration, including contaminant species like H2O, and after a pre-processing/data cleaning analysis which is also similar in both instruments. A first error analysis is performed for both instruments with the help of synthetic retrievals and a series of sensitivity tests performed with the same inversion scheme and similar treatment of the key error terms (measurement noise and systematics). Comparison of results We will present data obtained in the 2.7 µm region, dominated by a well known ro-vibrational band of CO2, and sampled by NOMAD-SO in a mixture of diffraction orders that are used routinely in the operational sounding in the vertical. Similarly, we used 3 consecutive orders in one of the ACS-MIR difraction positions, which contain a sufficient number of CO2 lines in the same 2.7 µm band with the capability to sample the whole atmosphere, up to about 180 km, in a single vertical scan. For both instruments the sounding of the lowest troposphere is limited by the amount of atmospheric dust, which is also retrieved simultaneously with CO2 and temperature. We will compare the vertical profiles obtained in a small sample of profiles from each instrument which span different seasons, latitudes and atmopheric dust loadings, during the first year of TGO operations. The comparisons take into account that the two instruments' individual solar occulation scans are non-coincident in time and space. Comparions are also peformed with results from similar efforts by other groups in the NOMAD and ACS teams [9]. Two important applications of the obtained retrievals are : (i) to supply the most appropriate inputs to the retrieval of other atmospheric species from the same instruments and the same scans, without the need to assume a prior or first guesses from global circulation models (GCM), see companion contributions to this conference [10,11], and (ii) to validate predictions from these GCMs, and therefore, to help to improve them, particularly at high altitudes and at the terminator, where these datasets are particularly valuable [1]. Acknowledgements The IAA/CSIC team acknowledges financial support from the State Agency for Research of the Spanish MCIU through the ‘Center of Excellence Severo Ochoa’ award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709) and funding by grant PGC2018-101836-B-100 (MCIU/AEI/FEDER, EU). ExoMars is a space mission of the European Space Agency (ESA) and Roscosmos. The NOMAD experiment is led by the Royal Belgian Institute for Space Aeronomy (IASB-BIRA), assisted by Co-PI teams from Spain (IAA-CSIC), Italy (INAF-IAPS), and the United Kingdom (Open University). US investigators were supported by the National Aeronautics and Space Administration. Thanks are extensive to all members of the NOMAD Science Team and the ACS Science Team. References [1] Lopez-Valverde et al., Space Sci Rev, 214, 29 (2018) [2] Vandaele et al., Space Science Reviews 214, 5, 2018 [3] Korablev et al., Space. Sci. Rev. 214, 7 (2018). [5] Funke, B., et al. , Atmos. Chem. Phys., 9(7), 2387–2411 (2009). [4] Jimenez-Monferrer et al., Icarus, 353, 113830 (2020), doi.org/10.1016/j.icarus.2020.113830. [6] Stiller et al., JQSRT, 72, 249–280 (2002) [7] von Clarmann et al., J. Geophys. Res. 108, 4746 (2003) [8] Lopez-Valverde et al., EPSC Abstracts, Vol. 14, EPSC2020-924 (2020), doi.org/10.5194/epsc2020-924 [9] Trompet et al., "Update on CO2 and temperature profiles retrievals from NOMAD-SO on board ExoMars TGO", contribution to this conference, EPSC 2021. [10] Brines et al., "Martian water vapor vertical profiles with data from solar occultation measurements by NOMAD onboard TGO/ExoMars", contribution to this conference, EPSC 2021. [11] Modak et al., "Retrieval of Martian CO vertical profiles from NOMAD solar occultation measurements", contribution to this conference, EPSC 2021.

Nitric oxide (NO) measurements from the Solar Occultation for Ice Experiment (SOFIE) are validated through detailed uncertainty analysis and comparisons with independent observations. SOFIE was compared with coincident satellite measurements from the Atmospheric Chemistry Experiment (ACE) - Fourier Transform Spectrometer (FTS) instrument and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument. The comparisons indicate mean differences of less than ĝ1/450 % for altitudes from roughly 50 to 105 km for SOFIE spacecraft sunrise and 50 to 140 km for SOFIE sunsets. Comparisons of NO time series show a high degree of correlation between SOFIE and both ACE and MIPAS for altitudes below ĝ1/4130 km, indicating that measured NO variability in time is robust. SOFIE uncertainties increase below ĝ1/480 km due to interfering H2O absorption and signal correction uncertainties, which are larger for spacecraft sunrise compared to sunset. These errors are sufficiently large in sunrises that reliable NO measurements are infrequent below 80 km.© Author(s) 2019., This research has been supported by NASA (grant no. NAS5-03132, Heliophysics Guest Investigator project 80NSSC19K0281).

Precipitating auroral and radiation belt electrons are considered an important part of the natural forcing of the climate system. Recent studies suggest that this forcing is underestimated in current chemistry-climate models. The HEPPA III intercomparison experiment is a collective effort to address this point. Here, eight different estimates of medium energy electron (MEE) (>30 keV) ionization rates are assessed during a geomagnetic active period in April 2010. The objective is to understand the potential uncertainty related to the MEE energy input. The ionization rates are all based on the Medium Energy Proton and Electron Detector (MEPED) on board the NOAA/POES and EUMETSAT/MetOp spacecraft series. However, different data handling, ionization rate calculations, and background atmospheres result in a wide range of mesospheric electron ionization rates. Although the eight data sets agree well in terms of the temporal variability, they differ by about an order of magnitude in ionization rate strength both during geomagnetic quiet and disturbed periods. The largest spread is found in the aftermath of the geomagnetic activity. Furthermore, governed by different energy limits, the atmospheric penetration depth varies, and some differences related to latitudinal coverage are also evident. The mesospheric NO densities simulated with the Whole Atmospheric Community Climate Model driven by highest and lowest ionization rates differ by more than a factor of eight. In a follow-up study, the atmospheric responses are simulated in four chemistry-climate models and compared to satellite observations, considering both the model structure and the ionization forcing.

To improve our knowledge of the coupling of atmospheric circulation, composition and regional climate change, and to provide the urgently needed observations of the on-going changes and processes involved, we have recently proposed the Changing-Atmosphere Infra-Red Tomography Explorer (CAIRT) to ESA as Earth Explorer 11 candidate. CAIRT will be the first limb-sounder with imaging Fourier-transform infrared technology in space. By observing simultaneously the atmosphere from the troposphere to the lower thermosphere (about 5 to 115 km altitude), CAIRT will provide global observations of temperature, ozone, water vapour, as well as key halogen and nitrogen compounds. The latter will help to better constrain coupling with the upper atmosphere, solar variability and space weather. Observation of long-lived tracers (such as N2O, CH4, SF6, CF4) will provide information on transport, mixing and circulation changes. CAIRT will deliver essentially a complete budget of stratospheric sulfur (by observations of OCS, SO2, and H2SO4-aerosols), as well as observations of ammonia and ammonium nitrate aerosols. Biomass burning and other pollution plumes, and their impact on ozone chemistry in the UTLS region, will be detected from observations of HCN, CO and a further wealth of volatile organic compounds. The potential to measure water vapour isotopologues will help to constrain water vapour and cloud processes and interactions at the Earth’s surface. The high-resolution measurements of temperature will provide the momentum flux, phase speed and direction of atmospheric gravity waves. CAIRT thus will provide comprehensive information on the driving of the large-scale circulation by different types of waves. Tomographic retrievals will provide temperature and trace gas profiles at a much higher horizontal resolution and coverage than achieved from space so far. Flying in formation with the Second Generation Meteorological Operational Satellite (MetOp-SG) will enable combined retrievals with observations by the New Generation Infrared Atmospheric Sounding Interferometer (IASI-NG) and Sentinel-5, resulting in consistent atmospheric profile information from the surface up to the lower thermosphere. Our presentation will give an overview of the proposed CAIRT mission, its objectives and synergies with other sensors.

We present the impact of the so-called energetic particle precipitation (EPP), part of natural solar forcing on the atmosphere, on polar stratospheric NOx, ozone, and chlorine chemistry in the Antarctic springtime, using multi-satellite observations covering the overall period of 2005–2017. We find consistent ozone increases when high solar activity occurs during years with easterly phase of the quasi biennial oscillation. These ozone enhancements are also present in total O3 column observations. We find consistent decreases in springtime active chlorine following winters of elevated solar activity. Further analysis shows that this is accompanied by increase of chemically inactive chlorine reservoir species, explaining the observed ozone increase. This provides the first observational evidence supporting the previously proposed mechanism relating to EPP modulating chlorine driven ozone loss. Our findings suggest that solar activity via EPP has played an important role in modulating Antarctic ozone depletion in the last 15 years. As chlorine loading in the polar stratosphere continues to decrease in the future, this buffering mechanism will become less effective and catalytic ozone destruction by EPP produced NOx will likely become a major contributor to Antarctic ozone loss.

The spectroscopy of the υ = 1 → υ = 0 fundamental vibration-rotation band of nitric oxide (NO) in Earth's atmosphere is examined in depth in order to further assess the long-running dataset of infrared radiative cooling rates in the thermosphere from the SABER instrument on the NASA TIMED satellite. The fundamental band at 5.3 µm is shown to be almost solely responsible for the cooling by NO. The distribution of line strength in this band and the concentration of NO in the atmosphere are such that NO is remarkably transparent in Earth's atmosphere. Every fundamental band photon emitted in the nadir direction by NO in the thermosphere has a nearly 100% chance of hitting the Earth's surface before being absorbed by another NO molecule. The mean free paths of these photons exceed 5000 km. Vertical optical depths of the strongest NO absorption lines in 2 km thick layers in the thermosphere are less than 10−4 even during geomagnetically disturbed conditions. Consequently, nearly all of the radiation emitted by thermospheric NO escapes to space or to the lower atmosphere. Radiative excitation of thermospheric NO by upwelling infrared radiation (“earthshine”) from the troposphere is accurately assessed using measurements of infrared spectra made by the IASI instruments on the METOP satellites. Earthshine and solar excitation of NO are shown to compete with collisional excitation of NO by atomic oxygen below 110 km in polar regions and below 115 km in tropical regions. Therefore, NO 5.3 µm energy loss rates currently derived below ~ 115 km from measurements made by the SABER instrument on the NASA TIMED satellite are not representative of radiative cooling. Consequently, the current values of SABER-derived daily global power radiated from the thermosphere by NO are 5% to 15% too large. Approaches to further improve the SABER radiative cooling dataset are presented. © 2021., Mlynczak, Emmert, and Solomon acknowledge support from the Heliophysics Supporting Research Program of the NASA Heliophysics Division. Mlynczak, Hunt, and Russell also acknowledge support from the Thermosphere-Ionosphere-Mesosphere Energetics and Dynamics mission of the NASA Heliophysics Division., With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.

We present an analysis of the ionosphere and thermosphere response to Solar Proton Events (SPE) and magnetospheric proton precipitation in January 2005, which was carried out using the model of the entire atmosphere EAGLE. The ionization rates for the considered period were acquired from the AIMOS (Atmospheric Ionization Module Osnabrück) dataset. For numerical experiments, we applied only the proton-induced ionization rates of that period, while all the other model input parameters, including the electron precipitations, corresponded to the quiet conditions. In January 2005, two major solar proton events with different energy spectra and proton fluxes occurred on January 17 and January 20. Since two geomagnetic storms and several sub-storms took place during the considered period, not only solar protons but also less energetic magnetospheric protons contributed to the calculated ionization rates. Despite the relative transparency of the thermosphere for high-energy protons, an ionospheric response to the SPE and proton precipitation from the magnetotail was obtained in numerical experiments. In the ionospheric E layer, the maximum increase in the electron concentration is localized at high latitudes, and at heights of the ionospheric F2 layer, the positive perturbations were formed in the near-equatorial region. An analysis of the model-derived results showed that changes in the ionospheric F2 layer were caused by a change in the neutral composition of the thermosphere. We found that in the recovery phase after both solar proton events and the enhancement of magnetospheric proton precipitations associated with geomagnetic disturbances, the TEC and electron density in the F region and in topside ionosphere/plasmasphere increase at low- and mid-latitudes due to an enhancement of atomic oxygen concentration. Our results demonstrate an important role of magnetospheric protons in the formation of negative F-region ionospheric storms. According to our results, the topside ionosphere/plasmasphere and bottom-side ionosphere can react to solar and magnetospheric protons both with the same sign of disturbances or in different way. The same statement is true for TEC and foF2 disturbances. Different disturbances of foF2 and TEC at high and low latitudes can be explained by topside electron temperature disturbances. © 2020 COSPAR., This investigation of ionospheric response to SPE and magnetospheric protons was funded by RFBR according to the research project No. 18-55-52006. TS work on the SPE treatment in the HAMMONIA model and ER analysis of altitude-latitude distribution of the SPE induced ionization rates was supported by Russian Science Foundation (project No. 20-67-46016). The work benefited from the discussions in the framework of the International Space Science Institute teams "Space Weather Induced Direct Ionization Effects on The Ozone Layer" and "Relativistic Electron Precipitation and its Atmospheric Effect.", With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.

This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0/), which permits unrestricted reuse, distribution, and reproduction in any medium, provided the original work is properly cited., A new global set of atmospheric temperature profiles is retrieved from recalibrated radiance spectra recorded with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). Changes with respect to previous data versions include a new radiometric calibration considering the time dependency of the detector nonlinearity and a more robust frequency calibration scheme. Temperature is retrieved using a smoothing constraint, while tangent altitude pointing information is constrained using optimal estimation. ECMWF ERA-Interim is used as a priori temperature below 43 km. Above, a priori data are based on data from the Whole Atmosphere Community Climate Model Version 4 (WACCM4). Bias-corrected fields from specified dynamics runs, sampled at the MIPAS times and locations, are used, blended with ERA-Interim between 43 and 53 km. Horizontal variability of temperature is considered by scaling an a priori 3D temperature field in the orbit plane in a way that the horizontal structure is provided by the a priori while the vertical structure comes from the measurements. Additional microwindows with better sensitivity at higher altitudes are used. The background continuum is jointly fitted with the target parameters up to 58 km altitude. The radiance offset correction is strongly regularized towards an empirically determined vertical offset profile. In order to avoid the propagation of uncertainties of O3 and H2O a priori assumptions, the abundances of these species are retrieved jointly with temperature. The retrieval is based on HITRAN 2016 spectroscopic data, with a few amendments. Temperature-adjusted climatologies of vibrational populations of CO2 states emitting in the 15 µm region are used in the radiative transfer modeling in order to account for non-local thermodynamic equilibrium. Numerical integration in the radiative transfer model is now performed at higher accuracy. The random component of the temperature uncertainty typically varies between 0.4 and 1 K, with occasional excursions up to 1.3 K above 60 km altitude. The leading sources of the random component of the temperature error are measurement noise, gain calibration uncertainty, spectral shift, and uncertain CO2 mixing ratios. The systematic error is caused by uncertainties in spectroscopic data and line shape uncertainties. It ranges from 0.2 K at 20 km altitude for northern midlatitude summer conditions to 2.3 K at 12 km for tropical conditions. The estimated total uncertainty amounts to values between 0.6 K at 20 km for midlatitude summer conditions to 2.5 K at 12–15 km for tropical conditions. The vertical resolution varies around 3 km for altitudes below 50 km. The long-term drift encountered in the previous temperature product has been largely reduced. The consistency between high spectral resolution results from 2002 to 2004 and the reduced spectral resolution results from 2005 to 2012 has been largely improved. As expected, most pronounced temperature differences between version 8 and previous data versions are found in elevated stratopause situations. The fact that the phase of temperature waves seen by MIPAS is not locked to the wave phase found in ECMWF analyses demonstrates that our retrieval provides independent information and does not merely reproduce the prior information. © Author(s) 2021., This study was partly funded by DLR under contract no. 50EE1547 (SEREMISA). The IAA team was supported by MCIU under projects ESP2017-87143-R and PID2019-110689RB-I00/AEI/10.13039/501100011033. WACCM simulations are based upon work supported by the National Center for Atmospheric Research (NCAR), which is a major facility sponsored by the National Science Foundation under Cooperative Agreement no. 1852977., With funding from the Spanish government through the Severo Ochoa Centre of Excellence accreditation SEV-2017-0709.

We present simultaneous retrievals of vertical profiles of CO2 and temperature obtained from a small sample of solar occultation scans by the NOMAD-SO [1] and ACS-MIR [2] instruments on board the ExoMars Trace Gas Orbiter (TGO). The orbits or scans selected from each instrument's observations are sufficiently close in time and space so that the atmospheric variability plays a minor role and a meaningful comparison of the performance of both instrument channels is possible. This is an on-going work devoted to a proper validation of both instruments. We will present a small selection of retrievals than can be used for a critical analysis of the results obtained and as a first step into the mutual validation of NOMAD-SO and ACS-MIR.1. Instruments and observationsOur work is focussed in the NOMAD-SO and the ACS-MIR channels, those specifically devoted to operational observations in solar occultation. Several groups in the NOMAD and ACS teams are performing retrievals of species abundances from these signals and some are reported in this conference [3,4]. We focus on the retrieval of CO2 and temperature in the 2.7 µm range, the strongest IR bands by this gas in the spectra region coverd by SO and ACS [5]. The spectra correspond to calibrated transmittances derived from SO difraction orders 164 and 165 and from MIR position 4 spectra. About a dozen strong CO2 lines are observed in these spectra up to very high tangent altitudes, around 170-180 km. The present study targets at both solar occultation signals, NOMAD-SO and ACS-MIR, but unfortunately, due to some unexpected miss-alignments among the different channels in each instrument and between NOMAD and ACS, an entirely simultaneous observation of the solar disc as it emerges or hides behind the atmosphere is not possible with both SO and MIR channels. Instead this work study the inversions from the two channels in nearly coincident solar occultations, with small changes in latitude, longitude, solar longitude and time.2. Retrieval Scheme We have performed the present retrievals using an inversion code previously used in the Earth upper atmosphere for routine operations of the MIPAS instrument on board the Envisat mission [6]. The inversion scheme, which has been recently adapted to Mars for limb sounding in emission from the OMEGA spectrometer on board the Mars Express spacecraft [7], is adapted here for occultation observations. At the core of the inversion scheme is the forward model KOPRA (Karlsruhe Optimized and Precise Radiative transfer Algorithm [8] ) and the inversion processor (RCP), jointly developed by the Institute for Meteorology and Climate Research (IMK) and the IAA [9].As mentioned above we used here CO2 calibrated transmittances obtained from routine processing by the PI teams. But before injection into the inversion algorithm, a pre-processing of every orbit or scan is performed in order to correct every spectrum of spurious effects. These are essentially two: residual spectral shifts and artificial bending in single spectra. The magnitude of these two effects changes from order to order and between SO and ACS. In spite of these differences, the pre-processing is conceptually similar to both signals, and is actually performed with the same Python code. Further, the ILS associated to each of the signals is best reproduced by a double gaussian, whose detailed description (parameters describing their FWHM and peak ratios, for example) requires also a precise determination by the user, as apparently it slightly varies with time and observing conditions.It is specially useful to obtain both density and temperature information from a single scan, and this is the purpose of the present study. The simultaneous retrieval from a given scan actually derives a CO2 density profile, and after an iterative process, a temperature profile assuming hydrostatic equilibrium. An adjustment for the pointing is also intruduced, and the aerosol extinction and possible interference from species like H2O are also considered during the inversion to obtain the best fits.3. Results We will discuss the fist comparisons of CO2 and temperatures from NOMAD-SO and ACS-MIR, using a common pre-processing and inversion code. The retrievals perform in a similar manner, as in both cases the number of lines, the ro-vibrational bands and the spectral region are similar. Small differences in noise and spectral resolution have some impact but overall both channels permit sounding the Mars atmosphere up to the upper thermosphere with just one single scan. Averaging kernels indicate effective vertical resolutions around 4-6 km in the middle atmosphere (50-100 km), both in CO2 and temperature. The inversion is affected by heavy dust loading and in general degrades below about 30 km and above 150 km due to saturation and noise, respectively. AcknowledgementsThe IAA/CSIC team acknowledges financial support from the State Agency for Research of the Spanish MCIU through the ‘Center of Excellence Severo Ochoa’ award for the Instituto de Astrofísica de Andalucía (SEV-2017-0709). MALV was funded by grant PGC2018-101836-B-100 (MCIU/AEI/FEDER, EU). ExoMars is a space mission of the European Space Agency (ESA) and Roscosmos. The NOMAD experiment is led by the Royal Belgian Institute for Space Aeronomy (IASB-BIRA), assisted by Co-PI teams from Spain (IAA-CSIC), Italy (INAF-IAPS), and the United Kingdom (Open University). US investigators were supported by the National Aeronautics and Space Administration. References[1] Vandaele et al., Space Science Reviews 214 (5), 2018 [2] Korablev et al., Space. Sci. Rev. 214, 7 (2018). [3] Loic et al., Update on CO2 and temperature profiles retrievals from NOMAD-SO on board ExoMars TGO, contribution to this conference, 2020. [4] Shohei et al., Water vapor vertical profiles on Mars: Results from the first full Mars Year of TGO/NOMAD science operations, contribution to this conference, 2020. [5] Lopez-Valverde et al., Space Sci Rev (2018) 214:29 [6] Funke, B., et al. , Atmos. Chem. Phys., 9(7), 2387–2411, 2009.Funke et al., ACP, 9, 2387–2411, 2009. [7] Jimenez-Monferrer, Icarus in press, 2020 [8] Stiller et al., JQSRT, 72, 249–280, 2002 [9] von Clarmann et al., J. Geophys. Res. 108, 4746, 2003 How to cite: Lopez-Valverde, M. A., Funke, B., Hill, B., Gonzalez-Galindo, F., Aoki, S., Trompet, L., Thomas, I., Villanueva, G., Erwin, J., Olsen, K., Belyaev, D., Trokhimovskiy, A., Alday Parejo, J., Lopez-Puertas, M., Lopez-Moreno, J. J., Montmessin, F., Patel, M., Bellucci, G., Vandele, A. C., and Korablev, O.: CO2 and temperature retrievals in the Mars atmosphere from solar occultation by NOMAD-SO and ACS-MIR: performance and cross validation., Europlanet Science Congress 2020, online, 21 September–9 Oct 2020, EPSC2020-924, 2020

We investigate the impact of the so-called energetic particle precipitation (EPP) indirect effect on lower stratospheric ozone, ClO and ClONO2 in the Antarctic springtime. We use observations from Microwave Limb Sounder (MLS) and Ozone Monitoring Instrument (OMI) on Aura, Atmospheric Chemistry Experiment – Fourier Transform Spectrometer (ACE-FTS) on SciSat, and Michelson Interferometer for Passive Atmospheric Sound (MIPAS) on Envisat, covering the overall period of 2005–2017. Using the Ap index to proxy EPP, we find consistent ozone increases with elevated EPP during years with easterly phase of the quasi biennial oscillation (QBO) in both OMI and MLS observations. While these increases are opposite to what has been previously reported at higher altitudes, the pattern in the MLS O3 follows the typical descent patterns of EPP–NOx. The ozone enhancements are also present in the OMI total O3 column observations. Analogous to the descent patterns found in O3, we also found consistent decreases in springtime MLS ClO following winters of elevated EPP. To verify if this is due to a previously proposed mechanism of conversion of ClO to the reservoir species ClONO2 in reaction with NO2, we used ClONO2 observations from ACE-FTS and MIPAS. As ClO and NO2 are both catalysts in ozone destruction, the conversion into ClONO2 would result in ozone increase. We find a positive correlation between EPP and ClONO2 in the upper stratosphere in the early spring, and the lower stratosphere in late spring, providing the first observational evidence supporting the previously proposed mechanism relating to EPP–NOx modulating Clx driven ozone loss. Our findings suggest that EPP has played an important role in modulating ozone depletion in the last 15 years. As chlorine loading in the polar stratosphere continues to decrease in the future, this buffering mechanism will become less effective and catalytic ozone destruction by EPP–NOx will likely become a major contributor to Antarctic ozone loss.

This is an open access article.-- This work is distributed under the Creative Commons Attribution 4.0 License., 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. 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 front end 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 artefact 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 comparison instruments. © Author(s) 2020., This research has been supported by the Swedish National Space Agency (grant nos. Dnr 88/14 and Dnr 72/17) and the European Space Agency (Odin reprocessing, MesosphEO grant).

We present a non-local thermodynamic equilibrium retrieval scheme for atmospheric composition and its application to Mars CO2 infrared limb emissions as measured by the OMEGA instrument on board Mars Express (MEx). These emissions are caused by CO2 fluorescence of solar radiation, and thus the retrieval scheme accounts for non-LTE processes. We analyzed the dayside limb observations from a selection of three OMEGA orbits or data qubes. Before the retrieval was applied, we performed a radiometric calibration, cleaned the spectra (including clustering techniques) and generated radiance vertical profiles for each dataset. We also present information on the inversion set up, results on the retrieved CO2 density profiles, as well as the temperature profiles derived from the CO2 densities by assuming hydrostatic equilibrium. An extensive sensitivity study of the retrieval scheme was carried out, including its application to the OMEGA spectra taken at different MEx orbital configurations, to conclude on its performance and to offer recommendations for its systematic use with MEx datasets. The uncertainty due to the instrumental Gain calibration and that caused by the retrieval noise error itself are of large importance for the inversion, but a comparable component of the total error comes from the uncertainties of the temperature provided by the GCM. We demonstrated that, between 120 and 160 km, CO2 profiles can be derived with a precision around 30% and a vertical resolution of about 15 km. © 2020, This work was conducted as part of the project UPWARDS-633127 under the European Union's Horizon 2020 research and innovation Programme. The IAA team was supported by grant PGC2018-101836-B-100 ( MCIU/AEI/FEDER, EU ) and by the Spanish MCIU through the ‘Center of Excellence Severo Ochoa’ award to the IAA/CSIC ( SEV-2017-0709 ). OMEGA data are publicly available via the ESA Planetary Science Archive.