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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.

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.

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.

The atmospheric effects of precipitating electrons are not fully understood, and uncertainties are large for electrons with energies greater than ~30 keV. These electrons are underrepresented in modeling studies today, primarily because valid measurements of their precipitating spectral energy fluxes are lacking. This paper compares simulations from the Whole Atmosphere Community Climate Model (WACCM) that incorporated two different estimates of precipitating electron fluxes for electrons with energies greater than 30 keV. The estimates are both based on data from the Polar Orbiting Environmental Satellite Medium Energy Proton and Electron Detector (MEPED) instruments but differ in several significant ways. Most importantly, only one of the estimates includes both the 0° and 90° telescopes from the MEPED instrument. Comparisons are presented between the WACCM results and satellite observations poleward of 30°S during the austral winter of 2003, a period of significant energetic electron precipitation. Both of the model simulations forced with precipitating electrons with energies >30 keV match the observed descent of reactive odd nitrogen better than a baseline simulation that included auroral electrons, but no higher energy electrons. However, the simulation that included both telescopes shows substantially better agreement with observations, particularly at midlatitudes. The results indicate that including energies >30 keV and the full range of pitch angles to calculate precipitating electron fluxes is necessary for improving simulations of the atmospheric effects of energetic electron precipitation. ©2019. American Geophysical Union. All Rights Reserved., This research has been funded by the NASA Living With a Star program, grant NNX14AH54G, the NSF Frontiers of Earth System Dynamics program, grant AGS 1135432, and the NSF Coupling, Energetics and Dynamics of Atmospheric Regions, grant AGS 1651428. M. van de Kamp has been supported by the Academy of Finland project 276926 (SECTIC: Sun-Earth Connection Through Ion Chemistry). B. Funke acknowledges support by the Spanish MCINN (ESP2017-87143-R) and EC FEDER funds. We thank NCAR for the use of the WACCM model as well as their high-performance computing. The National Center for Atmospheric Research is operated by the University Corporation for Atmospheric Research under sponsorship of the National Science Foundation.

During the last 30 years, many works have focused on the determination of the CO abundance in Titan's atmosphere, but no measurement above 300km has been done yet, due to the faint emission of CO in the upper atmosphere. Nevertheless, such a study is particularly awaited as a conrmation of photochemical models that predict a uniform volume mixing ratio of CO in the whole atmosphere. Moreover, given that CO is the main atmospheric reservoir of oxygen, its actual abundance has implications on the origins of Titan's atmosphere. In this work, we analyse a set of Cassini VIMS daytime limb observations of Titan at 4.7 m, which is dominated by solar-pumped non-LTE emission of CO rovibrational bands. In order to study this non-LTE emission, we have developed a non-LTE model for CO vibrational levels. Retrieval of the CO concentration is performed following a bayesian approach and using the calculated non-LTE populations. The data set analysed is constituted by 45 limb scanning sequences - about two thousand spectra - obtained by VIMS in 2006 and 2007. CO relative abundance proles from 200 to 500km are obtained, for each set analysed. The average prole shows little variation with altitude ranging from 50 ppm at 200km to 60 ppm at 500 km. The measurements are however well compatible with a uniform volume mixing ratio prole of 55100 ppm, thus compatible with the prediction of photochemical models of a well-mixed vertical prole.

We present the validation of Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) CO2 daytime concentration in the mesosphere and lower thermosphere by comparing with Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) and Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) data. MIPAS shows a very good agreement with ACE below 100 km with differences of ∼5%. Above 100 km, MIPAS CO2 is generally lower than ACE with differences growing from ∼5% at 100 km to 20-40% near 110-120 km. Part of this disagreement can be explained by the lack of a non-local thermodynamic equilibrium correction in ACE. MIPAS also agrees very well (∼5%) with SABER below 100 km. At 90-105 km, MIPAS is generally smaller than SABER by 10-30% in the polar summers. At 100-120 km, MIPAS and SABER CO2 agree within ∼10% during equinox but, for solstice, MIPAS is larger by 10-25%, except near the polar summer. Whole Atmosphere Community Climate Model (WACCM) CO2 shows the major MIPAS features. At 75-100 km, the agreement is very good (∼5%), with maximum differences of ∼10%. At 95-115 km MIPAS CO2 is larger than WACCM by 20-30% in the winter hemisphere but smaller (20-40%) in the summer. Above 95-100 km WACCM generally overestimates MIPAS CO2 by about 20-80% except in the polar summer where underestimates it by 20-40%. MIPAS CO2 favors a large eddy diffusion below 100 km and suggests that the meridional circulation of the lower thermosphere is stronger than in WACCM. The three instruments and WACCM show a clear increase of CO2 with time, more markedly at 90-100 km.

The Visual and Infrared Mapping Spectrometer (VIMS) measurements of non-Local Thermodinamic Equilibrium (non-LTE) emissions of CH 4 , HCN and C 2 H 2 in the near-infrared represent a dataset with unique coverage to study Titan's upper atmosphere in the altitude range from 500 to 1000 km. This region is the key to a better understanding of the middle atmosphere circulation. The assessment of the latitudinal and seasonal variations in the distributions of HCN and C 2 H 2 could give important hints about it and complement the Composite InfraRed Spectrometer (CIRS) observations, that target the atmosphere below 500 km. The measurement of CH 4 and HCN above 900 km can also help in understanding the Ion and Neutral Mass Spectrometer (INMS) observations near and above 1000 km. We have analysed the VIMS daytime spectra in the 2.9–3.4 μm region measured from 2004 to 2012 that span from the mid-northern winter through mid-northern spring Titan seasons. The measurements exhibit very strong non-LTE emissions of CH 4 , HCN and C 2 H 2 . Non-LTE vibrational temperatures have been calculated for the emitting levels of the three molecules, and have been used in the inversion of their abundances in the 500–1100 km region. The retrieved abundances have been averaged in latitudinal bins and in two seasons: north hemisphere winter (2004–2009) and north hemisphere early spring (2010−2012). The C 2 H 2 average profile, retrieved for the first time from VIMS measurements, shows good agreement with UltraViolet Imaging Spectrograph (UVIS) measurements below 850 km, while higher values are found above that altitude. The HCN volume mixing ratio (VMR) shows an enhancement at the north pole during winter at all altitudes (from ∼700 km up to near 1000 km) and at the north and south poles during spring below 900 km. Also, the average C 2 H 2 abundance is larger at both poles during spring below 800 km, while no significant variation is seen during winter. For CH 4 we found enhancements above 800 km at the north pole during winter and at both poles during spring. Our results suggest that the middle atmosphere circulation on Titan extends well above the 500 km level, up to 750–800 km or even higher if we assume that the CH 4 concentration above 800 km is mainly controlled by the circulation. The behavior of CH 4 at the winter pole above 800 km is in line with the strong zonal winds suggested to explain INMS observations, although it can also be explained by the slower photo-dissociation occurring during polar winter. Despite the poor statistic at the polar regions, our results represent a unique dataset that could help to improve our understanding of Titan's atmosphere above 500 km. © 2019 Elsevier Inc., This research was completed thanks to the financial support of the Italian Space Agency (ASI) and NASA through the Cassini project. The IAA team was supported by the Spanish MICINN under project ESP2014-54362-P and EC FEDER funds. MGC was financially supported by MINECO through its 'Ramon y Cajal' subprogram.

Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited., Aims: We aim at detecting water vapor in the atmosphere of the hot Jupiter HD 209458 b and perform a multi-band study in the near infrared with CARMENES. Methods: The water vapor absorption lines from the atmosphere of the planet are Doppler-shifted due to the large change in its radial velocity during transit. This shift is of the order of tens of km s-1, whilst the Earth's telluric and the stellar lines can be considered quasi-static. We took advantage of this shift to remove the telluric and stellar lines using SYSREM, which performs a principal component analysis including proper error propagation. The residual spectra contain the signal from thousands of planetary molecular lines well below the noise level. We retrieve the information from those lines by cross-correlating the residual spectra with models of the atmospheric absorption of the planet. Results: We find a cross-correlation signal with a signal-to-noise ratio (S/N) of 6.4, revealing H2O in HD 209458 b. We obtain a net blueshift of the signal of -5.2 -1.3+2.6 km s-1 that, despite the large error bars, is a firm indication of day- to night-side winds at the terminator of this hot Jupiter. Additionally, we performed a multi-band study for the detection of H2O individually from the three near infrared bands covered by CARMENES. We detect H2O from its 0.96-1.06 ¿m band with a S/N of 5.8, and also find hints of a detection from the 1.06-1.26 ¿m band, with a low S/N of 2.8. No clear planetary signal is found from the 1.26-1.62 ¿m band. Conclusions: Our significant H2O signal at 0.96-1.06 ¿m in HD 209458 b represents the first detection of H2O from this band individually, the bluest one to date. The unfavorable observational conditions might be the reason for the inconclusive detection from the stronger 1.15 and 1.4 ¿m bands. H2O is detected from the 0.96-1.06 ¿m band in HD 209458 b, but hardly in HD 189733 b, which supports a stronger aerosol extinction in the latter, in line with previous studies. Future data gathered at more stable conditions and with larger S/N at both optical and near-infrared wavelengths could help to characterize the presence of aerosols in HD 209458 b and other planets.© A. Sánchez-López et al. 2019, CARMENES is funded by the German Max-Planck-Gesellschaft (MPG), the Spanish Consejo Superior de Investigaciones Cientificas (CSIC), the European Union through European Regional Fund (FEDER/ERF), the Spanish Ministry of Economy and Competitiveness, the state of Baden-Wurttemberg, the German Science Foundation (DFG), and the Junta de Andalucia, with additional contributions by the members of the CARMENES Consortium (Max-Planck-Institut fur Astronomie, Instituto de Astrofisica de Andalucia, Landessternwarte Konigstuhl, Institut de Ciencies de l'Espai, Institut fur Astrophysik Gottingen, Universidad Complutense de Madrid, Thuringer Landessternwarte Tautenburg, Instituto de Astrofisica de Canarias, Hamburger Sternwarte, Centro de Astrobiologia, and the Observatorio de Calar Alto). Financial support was also provided by the Universidad Complutense de Madrid, the Comunidad Autonoma de Madrid, the Spanish Ministerios de Ciencia e Innovacion and of Economia y Competitividad, the Fondo Europeo de Desarrollo Regional (FEDER/ERF), the Agencia estatal de investigacion, and the Fondo Social Europeo under grants AYA2011-30 147-C03-01, -02, and -03, AYA2012-39612-C03-01, ESP2013-48391-C4-1-R, ESP2014-54062-R, ESP 2016-76076-R, ESP2016-80435-C2-2-R, ESP2017-87143-R, BES-2015-073500, and BES-2015-074542. IAA authors acknowledge financial support from the State Agency for Research of the Spanish MCIU through the >Center of Excellence Severo Ochoa> award SEV-2017-0709. L.T.-O. acknowledges support from the Israel Science Foundation (grant No. 848/16). Based on observations collected at the Observatorio de Calar Alto. We thank the anonymous referee for their insightful comments, which contributed to improve the quality of the manuscript.

An analysis of recent observations (2004-2013) made by the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) instrument indicate that total carbon (COx=CO+CO2) has been increasing rapidly in the lower thermosphere, above 10(-3)hPa (90km). The estimated trend (similar to 9% per decade) is about a factor of 2 larger than the rate of increase that can be ascribed to anthropogenic emissions of CO2 (similar to 5% per decade). Here we investigate whether the observed trends of CO2 and COx can be reproduced using the Whole Atmosphere Community Climate Model (WACCM), a comprehensive global model with interactive chemistry, wherein vertical eddy diffusion is estimated from a parameterization of gravity wave breaking that can respond to changes in the model climate. We find that the modeled trends of CO2 and COx do not differ significantly at any altitude from the value expected from anthropogenic increases of CO2 and that WACCM does not produce significant changes in eddy diffusivity. We show that the discrepancy between model and observations cannot be attributed to uncertainties associated with geophysical noise and instrumental effects, to difficulties separating a linear trend from the 11year solar signal, or to sparse sampling by ACE-FTS. Estimates of the impact of vertical diffusion on CO2 in the model indicate that a large increase in K-zz (similar to 30% per decade) would be necessary to reconcile WACCM results with observations. It might be possible to ascertain whether such a large change in vertical mixing has in fact taken place by examining the trend of water vapor in the upper mesosphere. ©2016. American Geophysical Union. All Rights Reserved.”, R.R. Garcia and D.R. Marsh were supported in part by NASA grants X09AJ83G and NNX13AE33G, respectively. M. Lopez-Puertas and B. Funke were supported by MINECO (Spain) under grant ESP2014-54362-P and EC FEDER funds. WACCM is a component of NCAR's Community Earth System Model (CESM), which is supported by the National Science Foundation (NSF) and the Office of Science of the U.S. Department of Energy.

Jupiter's atmosphere has been sounded in transmission from the UV to the IR, as if it were a transiting exoplanet, by observing Ganymede while passing through Jupiter's shadow. The spectra show strong extinction due to the presence of aerosols and haze in Jupiter's atmosphere and strong absorption features of methane. Here, we report a new detailed analysis of these observations, with special emphasis on the retrievals of the vertical distribution of the aerosols and their sizes, and the properties and distribution of the stratospheric water ice. Our analysis suggests the presence of aerosols near the equator in the altitude range of 100 hPa up to at least 0.01 hPa, with a layer of small particles (mean radius of 0.1 μm) in the upper part (above 0.1 hPa), an intermediate layer of aerosols with a radius of 0.3 μm, extending between ∼10 and 0.01 hPa, and a layer with larger sizes of ∼0.6 μm at approximately 100-1 hPa. The corresponding loads for each layer are ∼2 × 10 g cm, ∼3.4 × 10 g cm, and ∼1.5 × 10 g cm, respectively, with a total load of ∼2.0 × 10 g cm. The lower and middle layers agree well with previous measurements; but the finer particles of 0.1 μm above 0.01 hPa have not been reported before. The spectra also show two broad features near 1.5 and 2.0 μm, which we attribute to a layer of very small (∼10 nm) HO crystalline ice in Jupiter's lower stratosphere (∼0.5 hPa). While these spectral signatures seem to be unequivocally attributable to crystalline water ice, they require a large amount of water ice to explain the strong absorption features.© 2018. The American Astronomical Society. All rights reserved., We are very grateful to Rafael Escribano, Victor Herrero, Anni Maattanen, Beatriz Mate, Agustin Sanchez-Lavega, and Miguel Angel Satorre for very valuable discussions on the water ice topic. The IAA team was supported by the Spanish MICINN under projects ESP2014-54362-P, ESP2017-87143-R, and EC FEDER funds. This work is also partly financed by the Spanish Ministry of Economics and Competitiveness through grant ESP2013-48391-C4-2-R. M.G.C. is also supported by the MINECO under its >Ramon y Cajal> subprogram.

PANIC is the new PAnoramic Near-Infrared Camera for Calar Alto and is a project jointly developed by the MPIA in Heidelberg, Germany, and the IAA in Granada, Spain, for the German-Spanish Astronomical Center at Calar Alto Observatory (CAHA; Almería, Spain). This new instrument works with the 2.2 m and 3.5 m CAHA telescopes covering a field of view of 30×30 arcmin and 15×15 arcmin, respectively, with a sampling of 4096×4096 pixels. It is designed for the spectral bands from Z to K, and can also be equipped with narrowband filters. The instrument was delivered to the observatory in 2014 October and was commissioned at both telescopes between 2014 November and 2015 June. Science verification at the 2.2 m telescope was carried out during the second semester of 2015 and the instrument is now at full operation. We describe the design, assembly, integration, and verification process, the final laboratory tests and the PANIC instrument performance. We also present first-light data obtained during the commissioning and preliminary results of the scientific verification. The final optical model and the theoretical performance of the camera were updated according to the as-built data. The laboratory tests were made with a star simulator. Finally, the commissioning phase was done at both telescopes to validate the camera real performance on sky. The final laboratory test confirmed the expected camera performances, complying with the scientific requirements. The commissioning phase on sky has been accomplished.© 2017. The Astronomical Society of the Pacific. All rights reserved., Part of this work was supported by the Spanish CSIC grants PIE-200450E175, 200450E458, 201250E108, 201250E012, and 201450E093, and MINECO grants AYA2010-10728 and ICTS-2009-32. L.V.M. acknowledges support from the grant AYA2015-65973-C3-1-R (MINECO/FEDER, UE).

The direct assimilation in 4D-Var of principal component (PC) scores derived from Infrared Atmospheric Sounding Interferometer (IASI) spectra has recently been demonstrated. To maximize the exploitation of the IASI instrument, a future step is to consider the extension of the PC approach to the extraction of information from the 4.3-μm CO-absorbing region. Shortwave IASI channels are currently underused compared to similar longwave channels because of day-night variations in data usability due to departures from local thermodynamic equilibrium (LTE). In this paper, we document the introduction of non-LTE (NLTE) effects in the PC-based version of the radiative transfer for TIROS operational vertical sounder (RTTOV) fast radiative transfer model (PC-RTTOV). The inclusion of NLTE effects in PC-RTTOV has required the development of a parameterized scheme that allows the fast computation of a NLTE correction to LTE radiances. The fast NLTE model is general enough to be applied to any sensor and can be utilized to add a fast and accurate NLTE correction to polychromatic LTE spectra computed by any general radiative transfer model, including RTTOV, which now incorporates the fast NLTE model developed in this study. The accuracy of the NLTE correction is such that daytime and nighttime radiances can be simulated to almost the same degree of accuracy. The comparison with IASI observations shows that the fast NLTE model presented here performs significantly better than the fast NLTE model incorporated in the previous version of RTTOV and also that improvements have to be made to the simulation of NLTE effects at winter high latitudes. ©2018. American Geophysical Union. All Rights Reserved., Marco Matricardi was jointly supported by ECMWF and EUMETSAT. M. Lopez-Puertas and B. Funke were supported by the Spanish MICINN under grant ESP2014-54362-P and EC FEDER funds. The Line-by-line Radiative Transfer Model (LBLRTM) used to compute the training data set of LTE and NLTE radiances is publicly available from the atmospheric and environmental research (AER) Radiative Transfer Working Group Website (http://rtweb.aer.com/lblrtm_frame.html). The vibrational temperature data sets can be accessed at http://www.iaa.es/similar to puertas/jgr_paper_2017.html. Finally, the ECMWF geophysical profiles used to compute the statistics of the O-B departures can be retrieved from the ECMWF archive by contacting ECMWF data services at data. services@ecmwf.int. For more information on ECMWF data services, the reader can consult the following web page: https://www.ecmwf.int/en/forecasts/accessingforecasts.

We present a retrieval of several vibrational-vibrational (V V) and vibrational-thermal (V-T) collisional rate coefficients affecting the populations of the CO2 levels emitting at 10, 4.3 and 2.7 μm from high-resolution limb atmospheric spectra taken by Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). This instrument has a high spectral resolution (0.0625 cm−1) and a wide spectral coverage (from 685 to 2410 cm−1) that allow measuring and discriminating among the many bands originating the atmospheric 4.3 μm radiance. Also its high sensitivity allows measuring the atmospheric limb emission in a wide altitude range, from 20 to 170 km in its middle and upper atmosphere modes, and hence obtain information on the temperature dependence of the collisional rates. In particular, we retrieve the rate coefficients and their temperature dependence in the 130–250 K range of the following processes: CO2(vd,v3)+N2⇌CO2(vd,v3−1)+N2(1) with vd=2v1+v2=2,3, and 4; CO2(v1,v2,l,1,r)+M⇌CO2(v1′,v2′,l′,1,r′)+M with Δvd=vd′−vd=0 and Δl = 0; and with Δvd=0 and Δl ≠ 0. In addition we have also retrieved the thermal relaxation of CO2(v3) into the v1 and v2 modes, e.g., CO2(vd,v3)+M⇌CO2(vd′,v3−1)+M with Δvd=2–4 and Δv3=−1 and the efficiency of the excitation of N2(1) by O(1D). All of them were retrieved with a much better accuracy than were known before. The new rates have very important effects on the atmospheric limb radiance in the 10, 4.3 and 2.7 μm spectral regions (5–8% at 4.3 μm) and allow a more accurate inversion of the CO2 volume mixing ratio in the mesosphere and lower thermosphere from measurements taken in those spectral regions.

International audience; SOIR is a powerful infrared spectrometer flying on board the Venus Express spacecraft since mid-2006. It sounds the Venus atmosphere above the cloud layer using the solar occultation technique. In the recorded spectra, absorption structures from many species are observed, among them carbon dioxide, the main constituent of the Venus atmosphere. Previously, temperature vertical profiles were derived from the carbon dioxide density retrieved from the SOIR spectra by assuming hydrostatic equilibrium. These profiles show a permanent cold layer at 125 km with temperatures of ~100 K, surrounded by two warmer layers at 90 and 140 km, reaching temperatures of ~200 K and 250–300 K respectively. In this work, temperature profiles are derived from the SOIR spectra using another technique based on the ro-vibrational structure of carbon dioxide observed in the spectra. The error budget is extensively investigated. Temperature profiles obtained by both techniques are comparable within their respective uncertainties and they confirm the vertical structure previously determined from SOIR spectra.

We present the first comprehensive intercomparison of currently available satellite ozone climatologies in the upper troposphere/lower stratosphere (UTLS) (300–70 hPa) as part of the Stratosphere-troposphere Processes and their Role in Climate (SPARC) Data Initiative. The Tropospheric Emission Spectrometer (TES) instrument is the only nadir-viewing instrument in this initiative, as well as the only instrument with a focus on tropospheric composition. We apply the TES observational operator to ozone climatologies from the more highly vertically resolved limb-viewing instruments. This minimizes the impact of differences in vertical resolution among the instruments and allows identification of systematic differences in the large-scale structure and variability of UTLS ozone. We find that the climatologies from most of the limb-viewing instruments show positive differences (ranging from 5 to 75%) with respect to TES in the tropical UTLS, and comparison to a “zonal mean” ozonesonde climatology indicates that these differences likely represent a positive bias for p ≤ 100 hPa. In the extratropics, there is good agreement among the climatologies regarding the timing and magnitude of the ozone seasonal cycle (differences in the peak-to-peak amplitude of

We have used the Whole Atmosphere Community Climate Model (WACCM) to calculate the distribution of CO2 and CO in the mesosphere and lower thermosphere (MLT), and we have compared the results with observations, mainly from the Atmospheric Chemistry Experiment Fourier Transform Spectrometer and Michelson Interferometer for Passive Atmospheric Sounding satellite-borne instruments. We find that WACCM can reproduce the observed distribution of CO2 in the MLT and the rapid falloff of CO2 above about 80 km. Analysis of the principal terms in the calculated budget of CO2 shows that its global-mean vertical profile is determined mainly by the competition between molecular diffusive separation and eddy mixing by gravity waves. The model underestimates somewhat the mixing ratio of CO2 in the thermosphere compared to that in the observations, but we show that the discrepancy may be eliminated by a reasonable adjustment of the Prandtl number used to calculate the diffusivity due to gravity waves. Simulated CO is also consistent with observations, except that in the standard version of the model, its mixing ratio is uniformly lower than observed above about 100 km. We conclude that WACCM likely underestimates the rate of production of CO in the lower thermosphere from photolysis of CO2 at wavelengths

Global distributions of the six principal reactive nitrogen (NOy) compounds (HNO3, NO2, NO, N2O5, ClONO2, and HNO4) have been derived from midinfrared limb emission spectra taken by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board Envisat during 2002–2012. The obtained data set provides a unique climatological record of NOy in the middle atmosphere. The contribution of NOy produced by energetic particle precipitation (EPP) has been discriminated from that produced by N2O oxidation using a tracer correlation method based on MIPAS CH4 and CO observations. The EPP-NOy distributions, obtained in the vertical range 20–70km, allow to trace odd nitrogen polar winter descent from the mesosphere down to the middle and lower stratosphere, where it contributes to catalytic ozone destruction. Highest EPP-NOy concentrations (up to 1 ppmv) are found in the winter solstice mesosphere, decreasing continuously with time and toward lower altitudes. Springtime peak concentrations of a few parts per billion by volume are observed at 22–25km, demonstrating a regular EPP impact on the entire stratosphere. The interannual variation shows a clear solar cycle signal in consonance with geomagnetic activity variations. A pronounced hemispheric asymmetry of EPP-NOy is observed, with higher concentrations in the Southern Hemisphere (SH) and stronger variability in the Northern Hemisphere (NH). Poleward of 60°, EPP-NOy contributes to the winter NOy column at 20–70km by 10–40% in the SH and 1–30% in the NH. Smaller contributions (0.1–1%) are found at midlatitudes (30°–60°). This study provides the first assessment of EPP-NOy intrusions into the stratosphere based on globally available satellite data on a decadal scale.

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 use, distribution, and reproduction in any medium, provided the original work is properly cited., We apply the Entire Atmosphere GLobal (EAGLE) model to investigate the upper atmosphere response to the January 2009 sudden stratospheric warming (SSW) event. The model successfully reproduces neutral temperature and total electron content (TEC) observations. Using both model and observational data, we identify a cooling in the tropical lower thermosphere caused by the SSW. This cooling affects the zonal electric field close to the equator, leading to an enhanced vertical plasma drift. We demonstrate that along with a SSW-related wind disturbance, which is the main source to form a dynamo electric field in the ionosphere, perturbations of the ionospheric conductivity also make a significant contribution to the formation of the electric field response to SSW. The post-sunset TEC enhancement and pre-sunrise electron content reduction are revealed as a response to the 2009 SSW. We show that at post-sunset hours the SSW affects low-latitude TEC via a disturbance of the meridional electric field. We also show that the phase change of the semidiurnal migrating solar tide (SW2) in the neutral wind caused by the 2009 SSW at the altitude of the dynamo electric field generation has a crucial importance for the SW2 phase change in the zonal electric field. Such changes lead to the appearance of anomalous diurnal variability of the equatorial electromagnetic plasma drift and subsequent low-latitudinal TEC disturbances in agreement with available observations. Plain Language Summary - Entire Atmosphere GLobal model (EAGLE) interactively calculates the troposphere, stratosphere, mesosphere, thermosphere, and plasmasphere-ionosphere system states and their response to various natural and anthropogenic forcing. In this paper, we study the upper atmosphere response to the major sudden stratospheric warming that occurred in January 2009. Our results agree well with the observed evolution of the neutral temperature in the upper atmosphere and with low-latitude ionospheric disturbances over America. For the first time, we identify an SSW-related cooling in the tropical lower thermosphere that, in turn, could provide additional information for understanding the mechanisms for the generation of electric field disturbances observed at low latitudes. We show that the SSW-related vertical electromagnetic drift due to electric field disturbances is a key mechanism for interpretation of an observed anomalous diurnal development of the equatorial ionization anomaly during the 2009 SSW event. We demonstrate that the link between thermospheric winds and the ionospheric dynamo electric field during the SSW is attained through the modulation of the semidiurnal migrating solar tide. © M.V. Klimenko et al., Published by EDP Sciences 2015., This investigation was performed with the financial support of the Russian Science Foundation Grant No. 17-17-01060. B. Funke acknowledges support by the Spanish MCINN (ESP2017-87143-R) and EC FEDER funds.

In this paper, observations by thermosphere, ionosphere, mesosphere energetics and dynamics/Sounding of the Atmosphere using Broadband Emission Radiometry from 2002 to 2012 and by Envisat/Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) from 2008 to 2009 are used to study the longitudinal structure of temperature in the lower thermosphere. In order to remove the longitudinal structure induced by tides, diurnally averaged SABER temperatures are used. For MIPAS data, we use averaged temperatures between day and night. The satellite observations show that there are strong longitudinal variations in temperature in the high-latitude lower thermosphere that persist over all seasons. The peak of the diurnally averaged temperature in the lower thermosphere always occurs around the auroral zone. A clear asymmetry between the two hemispheres in the longitudinal temperature structure is observed, being more pronounced in the Southern than in the Northern Hemisphere. In both hemispheres, the longitudinal variation is dominated by the first harmonic in longitude. The total radiative cooling observed by SABER has a structure in longitude that is similar to that of temperature. Modeling simulations using the Thermosphere-Ionosphere-Electrodynamics General Circulation Model reproduce similar features of the longitudinal variations of temperature in the lower thermosphere. Comparison of two model runs with and without auroral heating confirms that auroral heating causes the observed longitudinal variations. The multiyear averaged vertical structures of temperature observed by the two satellite instruments indicate that the impact of auroral heating on the thermodynamics of the neutral atmosphere can penetrate down to about 105 km.

[1] This paper explores the impact of diurnal tides that begin near the surface as heat is released by evaporation and condensation on Earth's upper atmosphere natural thermostat: the nitric oxide (NO) infrared cooling of the thermosphere at 5.3 μm. Equatorial NO volume emission rate measurements from 100 to 180 km made by Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) on TIMED during the solar minimum year 2008 are analyzed on two important nonmigrating tides, the DE2 and DE3 components. DE3 (DE2) amplitudes maximize around 125 km altitude and, depending on season, are on the order of 0.18 (0.16) nW/m3. This represents a substantial modulation of the mean NO emission that maximizes in the same altitude range with a value of about 0.8 nW/m3. Tropospheric tides are therefore important not only for the dynamics and electrodynamics of the ionosphere-thermosphere system but also for modulating the thermospheric energy budget. Supporting photochemical tidal modeling indicates that the main tidal coupling mechanism is the temperature dependence of the collisional excitation of the NO (ν=1) vibrational state. However, the response to vertical tidal advection is also important. It is in-phase with the response to temperature and contributes as much as 50% to the NO tides at and above the emission maximum. Neutral density tidal variations contribute about 25% but with a 9 h phase offset resulting in a net damping. These results imply that NO 5.3 μm emissions are a suitable proxy for studying tidal dynamics in the thermosphere where no global temperature measurements are available.

We investigate the influence of Middle Range Energy Electrons (MEE; typically 30-300 keV) precipitation on the atmosphere using the SOCOL3-MPIOM chemistry-climate model with coupled ocean. Model simulations cover the 2002-2010 period for which ionization rates from the AIMOS dataset and atmospheric composition observations from MIPAS are available. Results show that during geomagnetically active periods MEE significantly increase the amount of NO and HO in the polar winter mesosphere, in addition to other particles and sources, resulting in local ozone decreases of up to 35%. These changes are followed by an intensification of the polar night jet, as well as mesospheric warming and stratospheric cooling. The contribution of MEE also substantially enhances the difference in the ozone anomalies between geomagnetically active and quiet periods. Comparison with MIPAS NO observations indicates that the additional source of NO from MEE improves the model results, however substantial underestimation above 50 km remains and requires better treatment of the NO source from the thermosphere. A surface air temperature response is detected in several regions, with the most pronounced warming occurring in the Antarctic during austral winter. Surface warming of up to 2 K is also seen over continental Asia during boreal winter. © 2016 The Authors, This work has been supported by the Swiss National Science Foundation under Grant CRSII2-147659 (FUPSOL II). F. Tummon has been supported by the Swiss National Science Foundation under Project 20FI21_138017. This work is a part of ROSMIC WG1 activity within the SCOSTEP VarSITI program. We would also like to acknowledge the financial support by the Academy of Finland to the ReSoLVE Centre of Excellence (project no. 272157).

Cassini/VIMS limb observations have been used to retrieve vertical profiles of hydrogen cyanide (HCN) from its 3 μm emission in the region from 600 to 1100 km altitude at daytime. While the daytime emission is large up to about 1100 km, it vanishes at nighttime at very low altitudes, suggesting that the daytime emission originates under non-LTE conditions. The spectrally integrated radiances around 3.0 μm shows a monotonically decrease with tangent altitude, and a slight increase with solar zenith angle in the 40–80° interval around 800 km. A sophisticated non-LTE model of HCN energy levels has been developed in order to retrieve the HCN abundance. The population of the HCN 0 00 1 energy level, that contributes mostly to the 3.0 μm limb radiance, has been shown to change significantly with the solar zenith angle (SZA) and HCN abundance. Also its population varies with the collisional rate coefficients, whose uncertainties induced errors in the retrieved HCN of about 10% at 600–800 km and about 5% above. HCN concentrations have been retrieved from a set of spectra profiles, covering a wide range of latitudes and solar zenith angles, by applying a line-by-line inversion code. The results show a significant atmospheric variability above ∼800 km with larger values for weaker solar illumination. The HCN shows a very good correlation with solar zenith angles, irrespective of latitude and local time, suggesting that HCN at these high altitudes is in or close to photochemical equilibrium. A comparison with UVS and UVIS measurements show that these are close to the lower limit (smaller SZAs) of the VIMS observations above 750 km. However, they are in reasonable agreement when combining the rather large UV measurement errors and the atmospheric variability observed in VIMS. A comparison of the mean profile derived here with the widely used profile reported by Yelle and Griffith (Yelle R.V., Griffith, C.A. [2003]. Icarus 166, 107–115) shows a good agreement for altitudes ranging from 850 to 1050 km, while below these altitudes our result exhibits higher concentrations.

We report here on CO limb observations in Mars, Venus and Earth and their model simulations. A comparative study of the CO emission, including the most recent spacecraft observations of the three planets’ atmospheres, has been performed. Strong daytime emissions near 4.7 μ m have been recently observed in the limb of the upper atmosphere of the three terrestrial planets by the Planetary Fourier Spectrometer on Mars Express ( Formisano et al., 2005 ), the Visible and Infrared Thermal Imaging Spectrometer on Venus Express ( Drossart et al., 2007 ), and the Michelson Interferometer for Passive Atmosphere Sounding on Envisat ( Fischer et al., 2008 ). Those emissions are produced by solar pumping of molecular vibrations and non-local thermodynamic equilibrium (non-LTE) models are used to explain them in a consistent framework for the three atmospheres. The maximum of the 4.7 μ m emission occurs on Venus between 90 and 110 km, on Mars above 60 km, and on Earth around 68 km. The observations show that the fundamental band dominates the CO non-LTE emission on Earth, while on Venus and Mars the larger contribution comes from the first hot band transition. The main goal of this study is to understand those differences and similarities with the help of theoretical simulations with optical thickness considerations, and compare the capability of space instrumentation for the remote sounding of the atmospheres in this spectral region.

After molecular nitrogen, methane is the most abundant species in Titan’s atmosphere and plays a major role in its energy budget and its chemistry. Methane has strong bands at 3.3 μm emitting mainly at daytime after absorption of solar radiation. This emission is strongly affected by non-local thermodynamic equilibrium (non-LTE) in Titan’s upper atmosphere and, hence, an accurate modeling of the non-LTE populations of the emitting vibrational levels is necessary for its analysis. We present a sophisticated and extensive non-LTE model which considers 22 CH4 levels and takes into account all known excitation mechanisms in which they take part. Solar absorption is the major excitation process controlling the population of the v3-quanta levels above 1000 km whereas the distribution of the vibrational energy within levels of similar energy through collisions with N2 is also of importance below that altitude. CH4–CH4 vibrational exchange of v4-quanta affects their population below 500 km. We found that the ν3 → ground band dominates Titan’s 3.3 μm daytime limb radiance above 750 km whereas the ν3 + ν4 → ν4 band does below that altitude and down to 300 km. The ν3 + ν2 → ν2, the 2ν3 → ν3, and the 13CH4 ν3 → ground bands each contribute from 5% to 8% at regions below 800 km. The ν3 + 2ν4 → 2ν4and ν2 + ν3 + ν4 → ν2 + ν4 bands each contribute from 2% to 5% below 650 km. Contributions from other CH4 bands are negligible. We have used the non-LTE model to retrieve the CH4 abundance from 500 to 1100 km in the southern hemisphere from Cassini–VIMS daytime measurements near 3.3 μm. Our retrievals show good agreement with previous measurements and model results, supporting a weak deviation from well mixed values from the lower atmosphere up to 1000 km.

International audience; The MIPAS instrument on board Envisat, in Earth orbit, the PFS and OMEGA instruments on Mars Express, and VIRTIS on board Venus Express are currently providing a dataset of limb measurements of the CO 2 atmospheric fluorescence emission at 4.3-mum from the upper atmosphere of the three planets. These measurements represent an excellent dataset to perform comparative studies between the terrestrial planets' upper atmospheres, and also to test our theoretical understanding of these emissions. In order to exploit these datasets, we apply a set of non-local thermodynamic equilibrium (non-LTE) models developed at the IAA/CSIC, in Granada, Spain, to a selection of data. In general, the models can explain the main spectral features of the measurements, and also the altitude and solar zenith angle variations. However, the simulations for Mars and Venus give an incorrect ratio of the emissions at two wavelengths, 4.4 and 4.32mum. In order to explain this deficiency, a revision of the most uncertain non-LTE energy transfer parameters has been performed. The quenching rate of nu3 quanta of high-energy CO 2 states by CO 2 itself could reduce the model-data discrepancy if increased by a factor 2-4, still within its current uncertainty range. This factor, however, is subject to the uncertainty in the thermal structure. A number of simulations with the non-LTE models were also used to study and compare the role of radiative transfer in this spectral region in the three terrestrial planets. Sensitivity studies of density and temperature are also presented, and they permit an analysis of how the differences between the planets and between the three instruments affect their sounding capabilities.

Gravity waves strongly influence the circulation and transport processes in the middle atmosphere. We analyze the sensitivity of the simulated mesospheric transport of nitrogen oxides (NOx) to differences in a parameterization of non-orographic gravity waves. After particularly strong sudden stratospheric warming (SSW) events as in January 2009, satellite instruments measured a strong mesospheric descent of NOx. However, this downward transport is in general underestimated in models covering this altitude range. We use simulations of the atmospheric general circulation and chemistry model HAMMONIA (Hamburg Model of Neutral and Ionized Atmosphere) to discuss both differences in a homogeneous background gravity wave source and a source related to frontal activity. The results show that the transport of NOx is highly sensitive to such differences. With a stronger gravity wave source, less NOx is transported after the SSW to the mesosphere and the elevated stratopause descends more rapidly to its climatological altitude. We observe the opposite by weakening the gravity wave sources yielding a better agreement with the observations. The amount of the transported NOx is controlled by the altitude at which momentum is deposited in the atmosphere. The higher the altitude where the momentum is deposited in the upper mesosphere, the stronger is the descent of NOx. A small wave amplitude favors the transition to turbulence at a higher altitude due to the exponential increase of the amplitude with height.

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board ENVISAT, provided global (pole-to-pole, the polar night winter regions) measurements of nearly all constituents of the NOy family (including NO, NO2, HNO3 and N2O5) from July 2002 to the end of March 2004 from the upper stratosphere up to the middle mesosphere. The inter-annual variability of the NO2 and HNO3 abundances in the Arctic and Antarctic winters from September 2002 through March 2004 was enormous with tremendous hemispheric asymmetry and extraordinary values in two winters. The origin of these variations and of the extreme measured values has been analyzed on the basis of the changing atmospheric dynamics (using the CH4 tracer) and solar activity, including the extraordinary solar protons events of Oct–Nov 2003.

The lifetime of nitrous oxide, the third-most-important human-emitted greenhouse gas, is based to date primarily on model studies or scaling to other gases. This work calculates a semiempirical lifetime based on Microwave Limb Sounder satellite measurements of stratospheric profiles of nitrous oxide, ozone, and temperature; laboratory cross-section data for ozone and molecular oxygen plus kinetics for O(1D); the observed solar spectrum; and a simple radiative transfer model. The result is 116 ± 9 years. The observed monthly-to-biennial variations in lifetime and tropical abundance are well matched by four independent chemistry-transport models driven by reanalysis meteorological fields for the period of observation (2005-2010), but all these models overestimate the lifetime due to lower abundances in the critical loss region near 32 km in the tropics. These models plus a chemistry-climate model agree on the nitrous oxide feedback factor on its own lifetime of 0.94 ± 0.01, giving N2O perturbations an effective residence time of 109 years. Combining this new empirical lifetime with model estimates of residence time and preindustrial lifetime (123 years) adjusts our best estimates of the human-natural balance of emissions today and improves the accuracy of projected nitrous oxide increases over this century. Key Points Nitrous oxide lifetime is computed empirically from MLS satellite data Empirical N2O lifetimes compared with models including interannual variability Results improve values for present anthropogenic and preindustrial emissions.© 2015. The Authors., Research at UCI was supported by NASA grants NNX09AJ47G and NNX13AL12G and DOE awards DE-SC0007021 and DE-SC0012536. N.M.D. was supported by UCI NSF REU 1005042. The GEOSCCM contribution was supported by the NASA MAP program. B.F. was supported by the Spanish MCINN under grant AYA2011-23552 and EC FEDER funds. Work at the Jet Propulsion Laboratory was performed under contract with NASA. The assistance of Ryan Fuller (at JPL) for the creation of MLS data sets used here is acknowledged. The GSFC 2-D model contribution was supported by the NASA Atmospheric Composition: Modeling and Analysis Program.

Daytime mesospheric limb emission spectra of ozone in the 4.8 μ m regime are analyzed with respect to vibrational excitation and relaxation processes. The data, which was obtained by the MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) instrument on board ESA's Environmental Satellite, is simulated by means of a non-local thermodynamic equilibrium (non-LTE) model utilizing O 3 -abundance, temperature, and pressure data from simultaneous retrievals in other spectral regions. The vibrational states of ozone depart from LTE due to the absorption of radiation from the lower atmosphere and due to the production of excited states in the O + O 2 + M → O 3 ( v ) + M recombination reaction. The energy flow into the ozone molecule as well as the collisional relaxation are highly uncertain. Model calculations that assume ozone formation at energies larger than 5000 cm - 1 underestimate the measured radiances by a factor of 2–3 in the 50–75 km altitude regime, if the nominal relaxation scheme is assumed. Agreement between measured and modeled radiances is achieved, if the collisional rates for the transformation of hot band stretching to bending quanta are reduced by about a factor of three, or if the quasi-nascent distribution of ozone favors vibrational states in the 3000 cm - 1 region.

Ozone volume mixing ratio (VMR) profiles are measured by the Michelson Interferometer for passive atmospheric sounding (MIPAS) on ENVISAT. The data sets produced by the science data processor at Institut fur Meteorologic und Klimaforschung (IMK), Germany are compared with those obtained by halogen occultation experiment (HALOE) on UARS and by sub-millimetre radiometer (SMR) on ODIN. For the stratospheric measurements taken during September/October 2002, the three instruments show reasonable agreement, with global mean differences within 0.1-0.3 ppmv. The typical zonal mean differences are of 0.4 ppmv for HALOE and 0.6 ppmv for SMR (4-6%) in the ozone VMR peak region at 25-30 km near the equator, though larger differences of 0.8-1 ppmv (8-10%) are also observed in a small latitude-altitude region in the tropic. A positive bias of about 0.2-0.4 ppmv in the MIPAS data in the 35-40 km region has also been found. Further studies are under way to explain these differences.

With the successful launch of the European Space Agency’s Envisat satellite new possibilities for global night-time measurements of middle atmospheric ozone have emerged. The GOMOS and MIPAS instruments on board Envisat are able to measure ozone in both day and night conditions, which is especially important in the mesosphere where the diurnal variations of ozone are substantial. In this paper, we present a comparison of MIPAS and GOMOS night-time measurements. We show individual measurement profiles as well as statistical average profiles of stratospheric and mesospheric ozone from both instruments. Our conclusion is that the two instruments are generally in a good agreement throughout the middle atmosphere.

Vertical profiles of O3 and NO2 abundances from the atmospheric instruments GOMOS (Global Ozone Monitoring by the Occultation of Stars), MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) and SCIAMACHY (Scanning Imaging Spectrometer for Atmospheric Chartography) all on-board the recently launched European Space Agency (ESA) Environmental Satellite (ENVISAT) are intercompared. These comparisons contribute to the validation of these data products by detecting systematic deviations, for example, wrong tangent height determinations, spectroscopic errors, and others. The cross comparison includes GOMOS data products retrieved by the GOMOS prototype processor from ACRI (Sophia Antipolis, France), the scientific SCIAMACHY data products from the Institute of Environmental Physics at University of Bremen (IUP) and the scientific MIPAS data products from the Institute for Meteorology and Climate Research in Karlsruhe (IMK) and Institute of Astrophysics in Andalusia (IAA). Coincident measurements were identified by limiting the time difference to 100 min (duration of one orbit) and less than 500 km between two observation points. When lower stratospheric ozone is strongly depleted during polar spring, a homogeneity condition was further imposed on the satellite measurements by requiring an upper limit on the potential vorticity difference at the 475 K isentrope between both observations. Since geographically coincident NO2 measurements of the three instruments are performed during different times of the day and NO2 has a rather strong diurnal variability, matches of NO2 profiles were compared only where the solar zenith angle difference was below 5� . First results of the cross comparison show an agreement within 15% between 21 and 40 km altitude for O3 profiles and an agreement within 20% between 27 and 40 km altitude for NO2 profiles among the GOMOS, MIPAS and SCIAMACHY measurements. � 2005 COSPAR. Published by Elsevier Ltd. All rights reserved.

In this work, we deal with the retrieval of O 3 from the upper atmosphere data from 20 to 100 km using the high spectral resolution measurements of MIPAS in the regions of 14 and 10 μm. Non-LTE modelling of the O 3 levels is included. Quality parameters of the retrievals and sensitivity tests for tuning the retrieval processor are presented. Day and nighttime O 3 profiles and zonal O 3 distribution for solstice conditions are shown to demonstrate the robustness and quality of the method. Finally a preliminary error assessment on the random and systematic errors, including non-LTE sources, is presented.

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is a high-resolution limb sounder on board the European polar platform ENVISAT, scheduled to be launched in 2001. A large number of atmospheric trace gases relevant to stratospheric ozone chemistry and global change are expected to be retrieved from the IR spectra covering a wide spectral range. While operational data analysis under responsibility of the European Space Agency is limited to conditions of local thermodynamic equilibrium (LTE), the analysis of limb radiances affected by non-LTE is left to scientific institutions. In this paper we present an innovative non-LTE retrieval method as part of the MIPAS semi-operational data processor developed at the Institut fur Meteorologie und Klimaforschung (IMK). The new approach enables the treatment of vibrational, rotational, and spin non-LTE as well as a dependence of the non-LTE state distribution on the retrieval target quantities. In a case study, the method has been tested for its application to the non-LTE analysis of 5.3 μm MIPAS radiances. The fundamental ro-vibrational band of nitric oxide emitting at 5.3 μm shows strong non-LTE effects arising from vibrational excitation of stratospheric NO and superposed thermospheric non-LTE emissions. A conventional non-LTE retrieval approach using ab initio vibrational temperatures of NO cannot be applied due to rotational and spin non-LTE in the thermosphere, and the dependence of stratospheric vibrational temperatures on the NO abundance itself. The ability of the developed non-LTE inversion tool to retrieve stratospheric NO abundances is demonstrated by retrieval simulations. The further application of this method to the simultaneous retrieval of NO and kinetic temperature in the thermosphere and the retrieval of important non-LTE process parameters has also been tested.

Monthly zonal mean climatologies of atmospheric measurements from satellite instruments can have biases due to the non-uniform sampling of the atmosphere by the instruments. We characterize potential sampling biases in stratospheric trace gas climatologies of the Stratospheric Processes and their Role in Climate (SPARC) Data Initiative using chemical fields from a chemistry climate model simulation and sampling patterns from 16 satellite-borne instruments. The exercise is performed for the long-lived stratospheric trace gases O3 and H2O. Monthly sample biases for O3 exceed 10% for many instruments in the high latitude stratosphere and in the upper troposphere/lower stratosphere, while annual mean sampling biases reach values of up to 20% in the same regions for some instruments. Sampling biases for H2O are generally smaller than for O3, although still notable in the upper troposphere/lower stratosphere and Southern Hemisphere high latitudes. The most important mechanism leading to monthly sampling bias is the non-uniform temporal sampling of many instruments, i.e., the fact that for many instruments, monthly means are produced from measurements which span less than the full month in question. Similarly, annual mean sampling biases are well explained by non-uniformity in the month-to-month sampling by different instruments. Non-uniform sampling in latitude and longitude are shown to also lead to non-negligible sampling biases, which are most relevant for climatologies which are otherwise free of sampling biases due to non-uniform temporal sampling.

The non-LTE vibrational, rotational and spin state distribution of NO(ν = 1,J,Ω) has been calculated. The daytime vibrational (ν = 1) state population was found to depart from LTE even at stratospheric altitudes due to the pumping of the (ν = 1) state by the photolysis of NO2. The rotational and spin degree of freedom is in non-LTE above 110 km. Non-LTE limb radiance spectra of the fundamental band at 5.3 μm as will be recorded by the MIPAS-B ballon borne experiment or, in the near future, by the MIPAS-ENVISAT space borne experiment (Fischer and Oelhaf, 1996) have been simulated. A retrieval strategy that takes into account this problem has been developed for the MIPAS-B instrument. Here, the stratospheric non-LTE state distribution is retrieved simultaneously with the NO volume mixing ratio (vmr) profile. Instead of multi-parameter retrieval of the state distribution in terms of a vibrational temperature profile, only one parameter describing the impact of the NO2 photolysis is retrieved additionally to the vmr profile. The feasibility of this approach for the application to MIPAS-ENVISAT data is discussed.

We investigate the interannual variability and hemispheric differences of reactive odd nitrogen produced by energetic particle precipitation (EPP-NOy) and transported into the stratosphere and lower mesosphere during polar winters in 2002–2012. For this purpose, EPP-NOy amounts derived from observations of the Michelson Interferometer for Passive Atmospheric Sounding by means of a tracer correlation method have been used. Southern hemispheric (SH) seasonal maximum EPP-NOy amounts transported below the 0.02 hPa level range from 0.5GM to 2.5GM in the 2009 and 2003 winters, respectively. Northern hemispheric (NH) amounts were typically 2–5 times smaller, with the exception of the 2003/2004 winter. This interhemispheric asymmetry is primarily caused by a reduction of the mesospheric descent rates in NH midwinter, as opposed to the SH. Hemispherically integrated NOy fluxes through given pressure levels reach up to 0.07GM/day at 0.1 hPa. A multilinear regression of the EPP-NOy evolution to the Ap index of the preceding months indicates that a large fraction of the SH interannual variability of EPP-NOy (excluding direct contributions by solar protons) can be linked to geomagnetic activity variations. This relationship holds throughout the winter and at all vertical levels where EPP-NOy is present. In the NH, a similar correlation is found until midwinter, however, breaking down afterward above 2 hPa in years with elevated stratopause occurrence. As an exception, EPP-NOy amounts in the Arctic winter 2004/2005 were much higher than in other NH winters with similar geomagnetic activity. We attribute this behavior to the unusually stable polar vortex in that winter, otherwise typical for the SH.

We use satellite observations and a numerical model to investigate polar nighttime ozone at the secondary maximum, around 90–95 km. Observations from the MIPAS and SABER satellite instruments indicate that the highest ozone mixing ratios are seen during the late fall to early winter period in both hemispheres and for all years examined. Simulations using the Whole Atmosphere Community Climate Model (WACCM) find qualitatively the same seasonal evolution. Analysis of WACCM results shows that the high ozone concentration is due in part to the relatively quiet dynamical conditions in early winter. The mean circulation, which brings warmer temperatures and higher concentrations of H, is weaker in early winter than during middle and late winter. H in the late fall to early winter period drops to the lowest levels seen during the year due to lack of a source from photochemistry, weak transport into the region by the mean circulation, and continual loss due to diffusive separation. The low concentration of H leads to higher ozone.

Variability in the chemistry of the upper stratosphere/lower mesosphere region has been analyzed focusing on high latitudes during the boreal winter in 2009 characterized by the strong sudden stratospheric warming (SSW) on 24 January. Data from Michelson Interferometer for Passive Atmospheric Sounding aboard Envisat and the Microwave Limb Sounder on Aura have been used to exemplify these changes. Record high (low) values of O3 and ClO (temperature and HCl) for the winters of 2005–2012, coupled with a simultaneous enhancement of ClONO2, have been observed in February 2009. This suggests that the very low temperatures favor a more effective ozone production and a greater O3/O ratio. The latter is the main factor controlling active chlorine partitioning. Increases of ClO lead to high ClONO2 concentrations in the upper stratosphere at high latitudes, where its photodissociation rate is smaller. Since this increase of ClONO2 happens at the expense of HCl, the region of high ClONO2 roughly coincides with the region of low HCl. Although this period was characterized by an elevated stratopause event, the investigated region was not influenced by the descent of mesospheric air rich in NOx. Some limited enhancements in NOx at ~1 hPa occurred at latitudes greater than 80°N after about 20 February, but they became consistent only in March. Intrusion of midlatitude air mostly occurred between the SSW and early February. Then, the sum of volume mixing ratios of ClONO2 + ClO + HCl remained approximately constant and close to the values of the other years. In contrast, it was up to 0.2 ppbv lower during the SSW period. These atypical chemical conditions occurred also in February 2006, but 2009 stands out for its long-lasting effects, which persisted until late March.

[1] Ozone profiles in the upper mesosphere (70–100 km) retrieved from nine instruments are compared. Ozone from the Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) instrument is used as the basis of comparison. Other measurements are from the Halogen Occultation Experiment, the High Resolution Doppler Imager, the Michelson Interferometer for Passive Atmospheric Sounding, the Global Ozone Monitoring by Occultation of Stars, the Atmospheric Chemistry Experiment—Fourier Transform Spectrometer, the Solar Occultation For Ice Experiment, the Optical Spectrograph and InfraRed Imaging System, and the Superconducting Submillimeter-Wave Limb-Emission Sounder. Comparisons of each data set with SABER using coincident profiles indicate agreement in the basic vertical profile of ozone but also some systematic differences in daytime ozone. Ozone from the SABER 9.6 μm channel is higher than the other measurements over the altitude range 60–80 km by 20–50%. Nighttime comparisons indicate better relative agreement (

In this paper, we analyze the strong unidentified emission near 3.28 μm in Titan's upper daytime atmosphere recently discovered by Dinelli et al. We have studied it by using the NASA Ames PAH IR Spectroscopic Database. The polycyclic aromatic hydrocarbons (PAHs), after absorbing UV solar radiation, are able to emit strongly near 3.3 μm. By using current models for the redistribution of the absorbed UV energy, we have explained the observed spectral feature and have derived the vertical distribution of PAH abundances in Titan's upper atmosphere. PAHs have been found to be present in large concentrations, about (2-3) × 104 particles cm–3. The identified PAHs have 9-96 carbons, with a concentration-weighted average of 34 carbons. The mean mass is ~430 u; the mean area is about 0.53 nm2; they are formed by 10-11 rings on average, and about one-third of them contain nitrogen atoms. Recently, benzene together with light aromatic species as well as small concentrations of heavy positive and negative ions have been detected in Titan's upper atmosphere. We suggest that the large concentrations of PAHs found here are the neutral counterpart of those positive and negative ions, which hence supports the theory that the origin of Titan main haze layer is located in the upper atmosphere.

Evaluating the representation of processes controlling tropical and subtropical tropospheric relative humidity (RH) in atmospheric general circulation models (GCMs) is crucial to assess the credibility of predicted climate changes. GCMs have long exhibited a moist bias in the tropical and subtropical mid and upper troposphere, which could be due to the mis-representation of cloud processes or of the large-scale circulation, or to excessive diffusion during water vapor transport. The goal of this study is to use observations of the water vapor isotopic ratio to understand the cause of this bias. We compare the three-dimensional distribution of the water vapor isotopic ratio measured from space and ground to that simulated by several versions of the isotopic GCM LMDZ. We show that the combined evaluation of RH and of the water vapor isotopic composition makes it possible to discriminate the most likely cause of RH biases. Models characterized either by an excessive vertical diffusion, an excessive convective detrainment or an underestimated in situ cloud condensation will all produce a moist bias in the free troposphere. However, only an excessive vertical diffusion can lead to a reversed seasonality of the free tropospheric isotopic composition in the subtropics compared to observations. Comparing seven isotopic GCMs suggests that the moist bias found in many GCMs in the mid and upper troposphere most frequently results from an excessive diffusion during vertical water vapor transport. This study demonstrates the added value of water vapor isotopic measurements for interpreting shortcomings in the simulation of RH by climate models. The mid-infrared FTIR retrievals have been performed in the framework of the project MUSICA (http://www.imk-asf.kit.edu/english/ musica), which is funded by the European Research Council under the European Community’s Seventh Framework Programme (FP7/2007– 2013)/ERC grant agreement 256961. This work was supported by NASA Energy and Water-cycle Study (07-NEWS07-0020) and NASA Atmospheric Composition program (NNX08AR23G).

[1] The Limb Infrared Monitor of the Stratosphere (LIMS) measured polar stratospheric enhancements of NO2 mixing ratios due to energetic particle precipitation (EPP) in the Arctic winter of 1978–1979. Recently reprocessed LIMS data are compared to more recent measurements from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) and the Atmospheric Chemistry Experiment Fourier transform spectrometer (ACE-FTS) to place the LIMS measurements in the context of current observations. The amount of NOx (NO + NO2) entering the stratosphere that has been created by EPP in the mesosphere and lower thermosphere (EPP-NOx) has been quantified for the 1978–1979 and 2002–2003 through 2008–2009 Arctic winters. The NO2 enhancements in the LIMS data are similar to those in MIPAS and ACE-FTS data in the Arctic winters of 2002–2003, 2004–2005, 2006–2007, and 2007–2008. The largest enhancement by far is in 2003–2004 (∼2.2 Gmol at 1500 K), which is attributed to a combination of elevated EPP and unusual dynamics that led to strong descent in the upper stratosphere/lower mesosphere in late winter. The enhancements in 2005–2006 and 2008–2009, during which large stratospheric NOx enhancements were caused by a dynamical situation similar to that in 2003–2004, are larger than in all the other years (except 2003–2004) at 3000 K. However, by 2000 K the enhancements in 2005–2006 (2008–2009) are on the same order of magnitude as (smaller than) all other years. These results highlight the importance of the timing of the descent in determining the potential of EPP-NOx for reaching the middle stratosphere.

The goal of this study is to determine how H2O and HDO measurements in water vapor can be used to detect and diagnose biases in the representation of processes controlling tropospheric humidity in atmospheric general circulation models (GCMs). We analyze a large number of isotopic data sets (four satellite, sixteen ground-based remote-sensing, five surface in situ and three aircraft data sets) that are sensitive to different altitudes throughout the free troposphere. Despite significant differences between data sets, we identify some observed HDO/H2O characteristics that are robust across data sets and that can be used to evaluate models. We evaluate the isotopic GCM LMDZ, accounting for the effects of spatiotemporal sampling and instrument sensitivity. We find that LMDZ reproduces the spatial patterns in the lower and mid troposphere remarkably well. However, it underestimates the amplitude of seasonal variations in isotopic composition at all levels in the subtropics and in midlatitudes, and this bias is consistent across all data sets. LMDZ also underestimates the observed meridional isotopic gradient and the contrast between dry and convective tropical regions compared to satellite data sets. Comparison with six other isotope-enabled GCMs from the SWING2 project shows that biases exhibited by LMDZ are common to all models. The SWING2 GCMs show a very large spread in isotopic behavior that is not obviously related to that of humidity, suggesting water vapor isotopic measurements could be used to expose model shortcomings. In a companion paper, the isotopic differences between models are interpreted in terms of biases in the representation of processes controlling humidity. Copyright © 2012 by the American Geophysical Union.

[1] We present vertically resolved thermospheric temperatures and NO abundances in terms of volume mixing ratio retrieved simultaneously from spectrally resolved 5.3 μm emissions recorded by the Michelson Interferometer for Passive Atmospheric Spectroscopy (MIPAS) in its upper atmospheric observation mode during 2005–2009. These measurements are unique since they represent the first global observations of temperature and NO for both day and night conditions taken from space. A retrieval scheme has been developed which accounts for vibrational, rotational and spin-orbit non-LTE distributions of NO. Retrieved polar temperature and NO profiles have a vertical resolution of 5–10 km for high Ap values, and degrade to 10–20 km for low Ap conditions. Though retrieved NO abundances depend strongly on the atomic oxygen profile used in the non-LTE modeling, observations can be compared to model results in a consistent manner by applying a simple correction. Apart from this, total retrieval errors are dominated by instrumental noise. The typical single measurement precision of temperature and NO abundances are 5–40 K and 10–30%, respectively, for high Ap values, increasing to 30–70 K for Tk and 20–50% for NO VMR for low Ap conditions. Temperature and NO profiles observed under auroral conditions are rather insensitive to smoothing errors related to the mapping of a priori profile shapes. However, for extra-polar and low Ap conditions, a potential systematic bias in the retrieved nighttime temperature and NO profiles related to smoothing errors has been identified from a comparison to Thermosphere Ionosphere Mesosphere Electrodynamics General Circulation Model (TIME-GCM) simulations. We have constructed a solar minimum monthly climatology of thermospheric temperature and NO from MIPAS observations taken during 2008–2009. MIPAS temperature distributions agree well, on average, with the Mass Spectrometer and Incoherent Scatter radar model (NRLMSISE-00), but some systematic differences exist. MIPAS temperatures are generally colder than NRLMSISE-00 in the polar middle thermosphere (mainly in the summer polar region) by up to 40 K; and are warmer than NRLMSISE-00 in the lower thermosphere around 120–125 km by 10–40 K. Thermospheric NO daytime distributions agree well with the Nitric Oxide Empirical Model (NOEM), based on Student Nitric Oxide Explorer (SNOE) observations. A comparison of MIPAS NO number density with the previous climatology for the declining phases of the solar cycle based on HALOE and SME data shows that MIPAS is generally larger with values ranging from 10 to 40%, except in the auroral region and at the equatorial latitudes above 130 km where the MIPAS/HALOE+SME ratio varies from 1.6 to 2. Day-night differences in MIPAS NO show daytime enhancements of up to 140% in the tropical and midlatitudes middle thermosphere. In the lower thermosphere, the diurnal amplitude is smaller and NO concentrations are generally higher during night by about 10–30%, particularly in the auroral regions.

A comprehensive quality assessment of the ozone products from 18 limb-viewing satellite instruments is provided by means of a detailed intercomparison. The ozone climatologies in form of monthly zonal mean time series covering the upper troposphere to lower mesosphere are obtained from LIMS, SAGE I/II/III, UARS-MLS, HALOE, POAM II/III, SMR, OSIRIS, MIPAS, GOMOS, SCIAMACHY, ACE-FTS, ACE-MAESTRO, Aura-MLS, HIRDLS, and SMILES within 1978–2010. The intercomparisons focus on mean biases of annual zonal mean fields, interannual variability, and seasonal cycles. Additionally, the physical consistency of the data is tested through diagnostics of the quasi-biennial oscillation and Antarctic ozone hole. The comprehensive evaluations reveal that the uncertainty in our knowledge of the atmospheric ozone mean state is smallest in the tropical and midlatitude middle stratosphere with a 1σ multi-instrument spread of less than ±5%. While the overall agreement among the climatological data sets is very good for large parts of the stratosphere, individual discrepancies have been identified, including unrealistic month-to-month fluctuations, large biases in particular atmospheric regions, or inconsistencies in the seasonal cycle. Notable differences between the data sets exist in the tropical lower stratosphere (with a spread of ±30%) and at high latitudes (±15%). In particular, large relative differences are identified in the Antarctic during the time of the ozone hole, with a spread between the monthly zonal mean fields of ±50%. The evaluations provide guidance on what data sets are the most reliable for applications such as studies of ozone variability, model-measurement comparisons, detection of long-term trends, and data-merging activities.

Within the SPARC Data Initiative, the first comprehensive assessment of the quality of 13 water vapor products from 11 limb-viewing satellite instruments (LIMS, SAGE II, UARS-MLS, HALOE, POAM III, SMR, SAGE III, MIPAS, SCIAMACHY, ACE-FTS, and Aura-MLS) obtained within the time period 1978-2010 has been performed. Each instrument's water vapor profile measurements were compiled into monthly zonal mean time series on a common latitude-pressure grid. These time series serve as basis for the ‘climatological’ validation approach used within the project. The evaluations include comparisons of monthly or annual zonal mean cross-sections and seasonal cycles in the tropical and extra-tropical upper troposphere and lower stratosphere averaged over one or more years, comparisons of inter-annual variability, and a study of the time evolution of physical features in water vapor such as the tropical tape recorder and polar vortex dehydration. Our knowledge of the atmospheric mean state in water vapor is best in the lower and middle stratosphere of the tropics and mid-latitudes, with a relative uncertainty of ±2-6% (as quantified by the standard deviation of the instruments’ multi-annual means). The uncertainty increases towards the polar regions (±10-15%), the mesosphere (±15%), and the upper troposphere/lower stratosphere below 100 hPa (±30-50%), where sampling issues add uncertainty due to large gradients and high natural variability in water vapor. The minimum found in multi-annual (1998-2008) mean water vapor in the tropical lower stratosphere is 3.5 ppmv (±14%), with slightly larger uncertainties for monthly mean values. The frequently used HALOE water vapor dataset shows consistently lower values than most other datasets throughout the atmosphere, with increasing deviations from the multi-instrument mean below 100 hPa in both the tropics and extra-tropics. The knowledge gained from these comparisons and regarding the quality of the individual datasets in different regions of the atmosphere will help to improve model-measurement comparisons (e.g. for diagnostics such as the tropical tape recorder or seasonal cycles), data merging activities, and studies of climate variability.

[1] We report on the infrared emission (10–13 μm) of polar mesospheric clouds (PMCs) as measured by Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board the Environmental Satellite (MIPAS/ENVISAT) during 19–21 July 2005 in the summer Northern Hemisphere. The spectral distribution of MIPAS radiances is well described by that simulated for ice particle emission at low temperatures and hence provides further evidence of the water ice nature of the PMC particles. The vertical profiles of integrated radiance clearly show an emission peak at tangent heights of 81–83 km, as expected from PMC emission. Ice particles' volume density retrieved from MIPAS spectra shows a layer of ice particles extending from 80.5 to 87 km and from about 60°N to the North Pole, well confined within the region where temperature is below approximately 150 K. The upper part of the ice particle layer then extends to altitudes higher than that observed by UV/visible measurements, which confirms the current understanding that PMCs cover the entire polar mesopause region. The altitude of the layer peak changes from 82.5–83 km at 70°N–90°N to slightly higher altitudes (83–85 km) at lower latitudes (60°N–70°N). MIPAS ice particle altitude/latitude distribution suggests that they are formed mainly close to the pole and then are transported upward and to lower latitudes by the ascending branch of the meridional circulation, confirming previous modeling.

The vast set of near global and continuous atmospheric measurements made by the SABER instrument since 2002, including daytime and nighttime kinetic temperature (T(sub k)) from 20 to 105 km, is available to the scientific community. The temperature is retrieved from SABER measurements of the atmospheric 15 micron CO2 limb emission. This emission separates from local thermodynamic equilibrium (LTE) conditions in the rarefied mesosphere and thermosphere, making it necessary to consider the CO2 vibrational state non-LTE populations in the retrieval algorithm above 70 km. Those populations depend on kinetic parameters describing the rate at which energy exchange between atmospheric molecules take place, but some of these collisional rates are not well known. We consider current uncertainties in the rates of quenching of CO2 (v2 ) by N2 , O2 and O, and the CO2 (v2 ) vibrational-vibrational exchange to estimate their impact on SABER T(sub k) for different atmospheric conditions. The T(sub k) is more sensitive to the uncertainty in the latter two and their effects depend on altitude. The T(sub k) combined systematic error due to non-LTE kinetic parameters does not exceed +/- 1.5 K below 95 km and +/- 4-5 K at 100 km for most latitudes and seasons (except for polar summer) if the Tk profile does not have pronounced vertical structure. The error is +/- 3 K at 80 km, +/- 6 K at 84 km and +/- 18 K at 100 km under the less favourable polar summer conditions. For strong temperature inversion layers, the errors reach +/- 3 K at 82 km and +/- 8 K at 90 km. This particularly affects tide amplitude estimates, with errors of up to +/- 3 K.