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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)

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.

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.