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Variations in the isotopologic composition of water vapour are fundamental for understanding the relative importance of different mechanisms of water vapour transport from the tropical upper troposphere to the lower stratosphere. Previous comparisons obtained from observations of H2O and HDO by satellite instruments showed discrepancies. In this work, newer versions of H2O and HDO retrievals from Envisat/MIPAS and SCISAT/ACE-FTS are compared. Specifically, MIPAS-IMK V5, MIPAS-ESA V8 and ACE-FTS V4.1/4.2 for the common period from February 2004 to April 2012 are compared for the first time through a profile-to-profile approach and comparison based on climatological structures. The comparison is essential for the scientific community to assess the quality of new satellite data products, a necessary procedure to validate further scientific work. Averaged stratospheric H2O profiles reveal general good agreement between 16 and 30 km. Biases derived from the profile-to-profile comparison are around zero between 16 and 30 km for MIPAS-IMK and ACE-FTS comparison. For HDO and δ D, low biases are found in the MIPAS-ESA and ACE-FTS comparison in the same range of altitudes, even if associated with a larger de-biased standard deviation. The zonally averaged cross sections of H2O and HDO exhibit the expected distribution that has been established in previous studies. For δ D the tropical depletion in MIPAS-ESA occurs at the top of the dynamical tropopause, but this minimum is found at higher altitudes in the ACE-FTS and MIPAS-IMK dataset. The tape recorder signal is present in H2O and HDO for the three databases with slight quantitative differences. The δ D annual variation for ACE-FTS data and MIPAS-ESA data is weaker compared to the MIPAS-IMK dataset, which shows a coherent tape recorder signal clearly detectable up to at least 30 km. The observed differences in the climatological δ D composites between databases could lead to different interpretations regarding the water vapour transport processes toward the stratosphere. Therefore, it is important to further improve the quality of level 2 products. [ABSTRACT FROM AUTHOR]

The Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) is currently providing the only measurements of vertically resolved chlorodifluoromethane (HCFC-22) from space. This study assesses the ACE-FTS HCFC-22 v5.2 product in the upper troposphere and lower stratosphere, as well as simulations of HCFC-22 from a 39-year specified dynamics run of the Canadian Middle Atmosphere Model (CMAM39) in the same region. In general, ACE-FTS HCFC-22 observations tend to agree with subsampled CMAM39 data to within ±5 %, except for between ∼ 15 and 25 km in the extratropical regions where ACE-FTS exhibits a negative bias of 5 %–30 % and near 6 km in the tropics where ACE-FTS exhibits a bias of - 15 %. When comparing against correlative satellite, aircraft, and balloon data, ACE-FTS typically exhibits a low bias on the order of 0 %–10 % between ∼ 5 and 15 km and is within ±15 % between ∼ 15 and 25 km. ACE-FTS, CMAM39, and surface flask measurements from the NOAA Global Monitoring Laboratory's surface air-sampling network all exhibit consistent tropospheric HCFC-22 trends ranging between 6.8 and 7.8 ppt yr -1 (within 95 % confidence) for 2004–2012 and between 3.1 and 4.7 ppt yr -1 (within 95 % confidence) for 2012–2018. Interhemispheric differences (IHDs) of HCFC-22 were also derived using ACE-FTS, NOAA, and CMAM39 data, and all three yielded consistent and correlated (r≥0.42) IHD time series, with the results indicating that surface IHD values decreased at a rate of 2.2 ± 1.1 ppt per decade between 2004 and 2018. [ABSTRACT FROM AUTHOR]

Observational monitoring of the stratospheric transport circulation, the Brewer–Dobson circulation (BDC), is crucial to estimate any decadal to long-term changes therein, a prerequisite to interpret trends in stratospheric composition and to constrain the consequential impacts on climate. The transport time along the BDC (i.e. the mean stratospheric age of air, AoA) can best be deduced from trace gas measurements of tracers which increase linearly with time and are chemically passive. The gas sulfur hexafluoride (SF 6) is often used to deduce AoA because it has been increasing monotonically since the ∼ 1950s, and previously its chemical sinks in the mesosphere have been assumed to be negligible for AoA estimates. However, recent studies have shown that the chemical sinks of SF 6 are stronger than assumed and become increasingly relevant with rising SF 6 concentrations. To adjust biases in AoA that result from the chemical SF 6 sinks, we here propose a simple correction scheme for SF 6 -based AoA estimates accounting for the time-dependent effects of chemical sinks. The correction scheme is based on theoretical considerations with idealized assumptions, resulting in a relation between ideal AoA and apparent AoA which is a function of the tropospheric reference time series of SF 6 and of the AoA-dependent effective lifetime of SF 6. The correction method is thoroughly tested within a self-consistent data set from a climate model that includes explicit calculation of chemical SF 6 sinks. It is shown within the model that the correction successfully reduces biases in SF 6 -based AoA to less than 5 % for mean ages below 5 years. Tests using only subsampled data for deriving the fit coefficients show that applying the correction scheme even with imperfect knowledge of the sink is far superior to not applying a sink correction. Furthermore, we show that based on currently available measurements, we are not able to constrain the fit parameters of the correction scheme based on observational data alone. However, the model-based correction curve lies within the observational uncertainty, and we thus recommend using the model-derived fit coefficients until more high-quality measurements are able to further constrain the correction scheme. The application of the correction scheme to AoA from satellites and in situ data suggests that it is highly beneficial to reconcile different observational estimates of mean AoA. [ABSTRACT FROM AUTHOR]

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat provided infrared limb emission spectra, which were used to infer global distributions of CFC-11, CFC-12, and HCFC-22. Spectra were analysed using constrained non-linear least-squares fitting. Changes with respect to earlier data versions refer to the use of version 8 spectra, the altitude range where the background continuum is considered, details of the regularization and microwindow selection, and the occasional joint fitting of interfering species, the use of new spectroscopic data, the joint fit of a tangent-height-dependent spectral offset, and the use of 2D temperature fields. In the lower stratosphere the error budget is dominated by uncertainties in spectroscopic data, while above this measurement noise is the leading error source. The vertical resolution of CFC-11 and CFC-12 is 2–3 km near the tropopause, about 4 km at 30 km altitude, and 6–10 km at 50 km. The vertical resolution of HCFC-22 is somewhat coarser, 3–4 km at the tropopause and 10–12 km at 35 km altitude. In the altitude range of interest, the horizontal resolution is typically limited by the horizontal sampling of the measurements, not by the smearing of the retrievals. Horizontal information displacement does not exceed 150 km , which can become an issue only for comparisons with model simulations with high horizontal resolution or localized in situ observations. Along with the regular data product, an alternative representation of the data on a coarser vertical grid is offered. These data can be used without consideration of the averaging kernels. The new data version provides improvement with respect to reduction of biases and improved consistency between the full- and reduced-resolution mission period of MIPAS. [ABSTRACT FROM AUTHOR]

The Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS) is currently providing the only measurements of vertically resolved chlorodifluoromethane (HCFC-22) from space. This study assesses the ACE-FTS HCFC-22 v5.2 product in the upper troposphere – lower stratosphere, as well as the simulated concentrations of HCFC-22 from a 39-year specified dynamics run of the Canadian Middle Atmosphere Model (CMAM39) in the same region. In general, ACE-FTS HCFC-22 observations tend to agree with subsampled CMAM39 data to within ±5 %, except for between ~15 and 25 km in the extratropical regions where ACE-FTS exhibits a negative bias of 5–30 %, and near 6 km in the tropics where ACE FTS exhibits a bias of 15 %. When comparing against correlative satellite, aircraft, and balloon data, ACE-FTS typically exhibits a low bias on the order of 0–10 % between ~5–15 km and is within ±15 % between ~15–25 km. ACE-FTS, CMAM39, and surface flask measurements from the NOAA Global Monitoring Laboratory's surface air-sampling network, all exhibit consistent tropospheric HCFC-22 trends ranging between 6.8 and 7.8 pptv/year (within 95 % confidence) for 2004–2012, and between 3.1 and 4.7 pptv/year (within 95 % confidence) for 2012–2018. Interhemispheric differences (IHD) of HCFC-22 concentrations were also derived using ACE-FTS, NOAA, and CMAM39 data, and all three yielded consistent and correlated (r≥0.42) IHD timeseries, with the results indicating that surface IHD values decreased at a rate of 2.2±1.1 pptv/decade between 2004 and 2018. [ABSTRACT FROM AUTHOR]

Motivated by an improved European Space Agency (ESA) version of calibrated Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) spectra (version 8.03), we have released version 8 of MIPAS temperatures and pointing information retrieved from 2005–2012 MIPAS measurements at 12–15 µ m in the Middle Atmosphere (MA), Upper Atmosphere (UA) and Noctilucent Cloud (NLC) measurement modes. The Institute of Meteorology and Climate Research–Instituto de Astrofisica de Andalucia (IMK–IAA) retrieval processor in use considers non-local thermodynamic equilibrium (non-LTE) emission explicitly for each limb scan. This non-LTE treatment is essential to obtain accurate temperatures above the mid-mesosphere because at the altitudes covered, up to 115 km, the simplified climatology-based non-LTE treatment employed for the Nominal (NOM) measurements is insufficient. Other updates in MA/UA/NLC version 8 non-LTE temperature retrievals from previous data releases include more realistic atomic oxygen and carbon dioxide abundances, an updated set of spectroscopic data, an improved spectral shift retrieval, a continuum retrieval extended to altitudes up to 58 km, consideration of an altitude-dependent radiance offset retrieval, the use of wider microwindows above 85 km to capture the offset, an improved accuracy in forward model calculations, new a priori temperature information, improved temperature horizontal gradient retrievals and the use of MIPAS version 5 interfering species where available. The resulting MIPAS MA/UA/NLC IMK–IAA temperature dataset is reliable for scientific analysis in the full measurement vertical range for the MA (18–102 km) and the NLC (39–102 km) observations and from 42 to 115 km for the UA observations. The random temperature errors, dominated by the instrumental noise, are typically less than 1 K below 60 km, 1–3 K at 60–70 km, 3–5 K at 70–90 km, 6–8 K at 90–100 km, 8–12 K at 100–105 km and 12–20 K at 105–115 km. Random pointing correction errors, also mainly arising from instrumental noise, are on average 50 m for tangent altitudes up to 60 km and decrease linearly to values smaller than 20 m for altitudes above 95 km. The vertical resolution is 3 km at altitudes below 50 km, 3–5 km at 50–70 km, 4–6 km at 70–90 km, 6–10 km at 90–100 km and 8–11 km at 100–115 km. The systematic errors in retrieved temperatures below 75 km are driven by uncertainties in the CO 2 spectroscopic data and, above 80 km, by uncertainties in the non-LTE model parameters (including collisional rates and atomic oxygen abundance) and the CO 2 abundance. These lead to systematic temperature errors of less than 0.7 K below 55 km, 1 K at 60–80 km, 1–2 K at 80–90 km, 3 K at 95 km, 6–8 K at 100 km, 10–20 K at 105 km and 20–30 K at 115 km. Systematic errors in the tangent altitude correction, mainly arising from CO 2 spectroscopic uncertainties, are 250 m at 20 km, 200 m at 40–60 km, 100 m at 80 km and smaller than 50 m above 90 km. The consistency between the MA/UA/NLC and the NOM IMK–IAA datasets is excellent below 70 km (typical 0.5–1 K differences). The comparison of this temperature dataset with co-located Sounding of the Atmosphere using Broadband Emission Radiometry (SABER) temperature measurements shows excellent agreement, with differences typically within 1.5 K below 90 km, 1–3 K at 90–95 km, 1–5 K at 95–100 km, 1–8 K at 100–105 km and 1–10 K above. The agreement with SABER improves with respect to previous MIPAS IMK–IAA data versions. [ABSTRACT FROM AUTHOR]

Satellite data records of stratospheric water vapour have been compared to balloon-borne frost point hygrometer (FP) profiles that are coincident in space and time. The satellite data records of 15 different instruments cover water vapour data available from January 2000 through December 2016. The hygrometer data are from 27 stations all over the world in the same period. For the comparison, real or constructed averaging kernels have been applied to the hygrometer profiles to adjust them to the measurement characteristics of the satellite instruments. For bias evaluation, we have compared satellite profiles averaged over the available temporal coverage to the means of coincident FP profiles for individual stations. For drift determinations, we analysed time series of relative differences between spatiotemporally coincident satellite and hygrometer profiles at individual stations. In a synopsis we have also calculated the mean biases and drifts (and their respective uncertainties) for each satellite record over all applicable hygrometer stations in three altitude ranges (10–30 hPa, 30–100 hPa, and 100 hPa to tropopause). Most of the satellite data have biases <10 % and average drifts <1 % yr -1 in at least one of the respective altitude ranges. Virtually all biases are significant in the sense that their uncertainty range in terms of twice the standard error of the mean does not include zero. Statistically significant drifts (95 % confidence) are detected for 35 % of the ≈ 1200 time series of relative differences between satellites and hygrometers. [ABSTRACT FROM AUTHOR]

Observational monitoring of the stratospheric transport circulation, the Brewer-Dobson-Circulation (BDC), is crucial to estimate any decadal to long-term changes therein, a prerequisite to interpret trends in stratospheric composition and to constrain the consequential impacts on climate. The transport time along the BDC (i.e., the mean age of stratospheric air, AoA) can best be deduced from trace gas measurements of tracers which increase linearly in time and are chemically passive. The gas SF 6 is often used to deduce AoA, because it has been increasing monotonically since the ~1950s, and previously its chemical sinks in the mesosphere have been assumed to be negligible for AoA estimates. However, recent studies have shown that the chemical sinks of SF 6 are stronger than assumed, and become increasingly relevant with rising SF 6 concentrations. To adjust biases in AoA that result from the chemical SF 6 sinks, we here propose a simple correction scheme for SF 6-based AoA estimates accounting for the time-dependent effects of chemical sinks. The correction scheme is based on theoretical considerations with idealized assumptions, resulting in a relation between ideal AoA and apparent AoA which is a function of the tropospheric reference time-series of SF 6 and of the AoA-dependent effective lifetime of SF 6. The correction method is thoroughly tested within a self-consistent data set from a climate model that includes explicit calculation of chemical SF 6 sinks. It is shown within the model that the correction successfully reduces biases in SF 6-based AoA to less than 5 % for mean ages below 5 years. Tests with using only sub-sampled data for deriving the fit coefficients show that applying the correction scheme even with imperfect knowledge of the sink is far superior to not applying a sink correction. Further, we show that based on currently available measurements, we are not able to constrain the fit parameters of the correction scheme based on observational data alone. However, the model-based correction curve lies within the observational uncertainty, and we thus recommend to use the model-derived fit coefficients until more high-quality measurements will be able to further constrain the correction scheme. The application of the correction scheme to AoA from satellites and in-situ data suggests that it is highly beneficial to reconcile different observational estimates of mean AoA. [ABSTRACT FROM AUTHOR]

The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat provided infrared limb emission spectra, which were used to infer global distributions of CFC-11, CFC-12, and HCFC-22. Spectra were analyzed using constrained non-linear least squares fitting. Changes with respect to earlier data versions refer to the use of version 8 spectra, the altitude range where the background continuum is considered, details of the regularization and microwindow selection, and the occasional joint-fitting of interfering species, new spectroscopic data, the joint-fit of a tangent-height dependent spectral offset, and the use of 2D temperature fields. In the lower stratosphere the error budget is dominated by uncertainties in spectroscopic data, while above measurement noise is the leading error source. The vertical resolution of CFC-11 and CFC-12 is 2-3 km near the tropopause, about 4 km at 30 km altitude and 6-10 km at 50 km. The vertical resolution of HCFC-22 is somewhat coarser, 3-4 km at the tropopause and 10-12 km at 35 km altitude. In the altitude range of interest, the horizontal resolution is typically limited by the horizontal sampling of the measurements, not by the smearing of the retrieval. Horizontal information displacement does not exceed 150 km, which can become an issue only for comparisons with model simulations with high horizontal resolution or localized in-situ observations. Along with the regular data product, an alternative representation of the data on a coarser vertical grid is offered. These data can be used without consideration of the averaging kernels. The new data version provides improvement with respect to reduction of biases and improved consistency between the full and reduced resolution mission period of MIPAS. [ABSTRACT FROM AUTHOR]

Variations in the isotopological composition of water vapour are fundamental for understanding the relative importance of different mechanisms of water vapor transport from the tropical upper troposphere to the lower stratosphere. Previous comparisons obtained from observations of H2O and HDO by satellite instruments showed discrepancies. In this work, newer versions of H2O and HDO retrievals from Envisat/MIPAS are compared with data derived from SCISAT/ACE-FTS. Specifically, MIPAS-IMK V5, MIPAS-ESA V8, and ACE-FTS V4.1/4.2 for the common period from February 2004 to April 2012 are compared for the first time through a profile-to-profile approach and comparison based on climatological structures. Stratospheric H2O and HDO global average coincident profiles reveal good agreement. The smallest biases are found between 20 and 30 km, and the largest biases are exhibited around 40 km both in absolute and relative terms. For HDO, biases between -8.6–10.6 % are observed among the three databases in the altitudes of 16 to 30 km. However, around 40 km, ACE-FTS agrees better to MIPAS-IMK than MIPAS-ESA, with biases of -4.8 % and -37.5 %, respectively. The HDO bias between MIPAS-IMK and MIPAS ESA is 28.1 % at this altitude. The meridional cross-sections of H2O and HDO exhibit the expected distribution that has been established in previous studies. The tape recorder signal is present in H2O and HDO for the three databases with slight quantitative differences. The meridional cross-sections of δD are in good agreement with the previous version of MIPAS-IMK and ACE-FTS data. In the temporal δD variations, the results suggest that in the current data versions, the calculated isotopic composition (δD) from MIPAS-IMK aligns more closely with expected stratospheric behavior for the entire stratosphere. Nevertheless, there are differences in the climatological δD composites between databases that could lead to different interpretations regarding the water vapor transport processes toward the stratosphere, so it is important to intercompare these δD observations. [ABSTRACT FROM AUTHOR]

Variations in the isotopological composition of water vapour are fundamental for understanding the relative importance of different mechanisms of water vapor transport from the tropical upper troposphere to the lower stratosphere. Previous comparisons obtained from observations of H2O and HDO by satellite instruments showed discrepancies. In this work, newer versions of H2O and HDO retrievals from Envisat/MIPAS are compared with data derived from SCISAT/ACE-FTS. Specifically, MIPAS-IMK V5, MIPAS-ESA V8, and ACE-FTS V4.1/4.2 for the common period from February 2004 to April 2012 are compared for the first time through a profile-to-profile approach and comparison based on climatological structures. Stratospheric H2O and HDO global average coincident profiles reveal good agreement. The smallest biases are found between 20 and 30 km, and the largest biases are exhibited around 40 km both in absolute and relative terms. For HDO, biases between -8.6-10.6 % are observed among the three databases in the altitudes of 16 to 30 km. However, around 40 km, ACE-FTS agrees better to MIPAS-IMK than MIPAS-ESA, with biases of -4.8% and -37.5%, respectively. The HDO bias between MIPAS-IMK and MIPAS ESA is 28.1 % at this altitude. The meridional cross-sections of H2O and HDO exhibit the expected distribution that has been established in previous studies. The tape recorder signal is present in H2O and HDO for the three databases with slight quantitative differences. The meridional cross-sections of (δD are in good agreement with the previous version of MIPAS-IMK and ACE-FTS data. In the temporal (δD variations, the results suggest that in the current data versions, the calculated isotopic composition ((δD) from MIPAS-IMK aligns more closely with expected stratospheric behavior for the entire stratosphere. Nevertheless, there are differences in the climatological (δD composites between databases that could lead to different interpretations regarding the water vapor transport processes toward the stratosphere, so it is important to intercompare these (δD observations. [ABSTRACT FROM AUTHOR]

Motivated by an improved ESA version of MIPAS calibrated spectra (version 8.03), we have released version 8 of MIPAS temperatures and pointing information retrieved from 2005-2012 MIPAS measurements at 12-15 µm in the Middle Atmosphere (MA), Upper Atmosphere (UA) and Noctilucent Cloud (NLC) measurement modes. The IMK/IAA retrieval processor in use considers non-local thermodynamic equilibrium (non-LTE) emission explicitly for each limb scan. This non-LTE treatment is essential to obtain accurate temperatures above the mid-mesosphere, because at the altitudes covered, up to 115 km, the simplified climatology-based non-LTE treatment employed for the nominal (NOM) measurements is insufficient. Other updates in MA/UA/NLC V8 non-LTE temperature retrievals from previous data releases include: more realistic atomic oxygen and carbon dioxide abundances; an updated set of spectroscopic data; an improved spectral shift retrieval; a continuum retrieval extended to altitudes up to 58 km; consideration of an altitude-dependent radiance offset retrieval; the use of wider microwindows above 85 km to capture the offset; an improved accuracy in forward model calculations; new temperature a priori information; improved temperature horizontal gradient retrievals; and, the use of MIPAS version 5 interfering species, where available. The resulting MIPAS MA/UA/NLC IMK/IAA temperature dataset is reliable for scientific analysis in the full measurement vertical range for the MA (18-102 km) and the NLC (39-102 km) observations, and from 42 to 115 km for the UA observations. The random temperature errors, dominated by the instrumental noise, are typically less than 1K below 60 km, 1-3K at 60-70 km, 3-5K at 70-90 km, 6-8K at 90-100 km, 8-12K at 100-105 km and 12-20K at 105-115 km. Pointing correction random errors, also mainly arising from instrumental noise, are on average 50m for tangent altitudes up to 60 km and decrease linearly to values smaller than 20m for altitudes above 95 km. The vertical resolution is 3 km at altitudes below 50 km, 3-5 km at 50-70 km, 4-6 km at 70-90 km, 6-10 km at 90-100 km and 8-11 km at 100-115 km. The systematic errors of retrieved temperatures below 75 km are driven by uncertainties in the CO2 spectroscopic data and, above 80 km, by uncertainties in the non-LTE model parameters (including collisional rates and atomic oxygen abundance) and the CO2 abundance. These lead to systematic temperature errors of less than 0.7K below 55 km, 1K at 60-80 km, 1-2K at 80-90 km, 3K at 95 km, 6-8K at 100 km, 10-20K at 105 km and 20-30K at 115 km. Systematic errors in the tangent altitude correction, mainly arising from CO2 spectroscopic uncertainties, are 250m at 20 km and 200m at 40-60 km, 100m at 80 km and smaller than 50m above 90 km. The consistency between the MA/UA/NLC and the NOM IMK/IAA datasets is excellent below 70 km (typical 0.5-1K differences). The comparison of this V8 temperature dataset with co-located SABER temperature measurements shows an excellent agreement, even better than in previous MIPAS IMK/IAA versions. [ABSTRACT FROM AUTHOR]

Using the IMK/IAA data processor, methane and nitrous oxide distributions were retrieved from version 8 limb emission spectra recorded with the Michelson Inferferometer for Passive Atmospheric Sounding (MIPAS). The dataset includes measurements from the Nominal, UTLS-1, Middle Atmosphere, Upper Atmosphere and Noctilucent Cloud observation modes. The processing differs from the previous version 5 data with respect to the atmospheric state variables jointly retrieved with the target gases CH4 and N2O, the treatment of the radiance offset, the selection of microwindows, the regularization, the spectroscopic data used and the treatment of horizontal variability of the atmospheric state. Besides the regular data product, a coarse-grid representation of the profiles with unity averaging kernels is available, as well as a specific research product for Middle Atmosphere measurements resulting from a slightly different retrieval approach. The CH4 errors are dominated by the large spectroscopic uncertainty for line intensities, which probably is too pessimistic, and estimated to be 21–34 % in the altitude range 6–68 km for northern midlatitude summer day conditions. The N2O errors are 7–17 % below 45 km. At higher altitudes they increase strongly due to nearly vanishing N2O amounts. Analysis of the horizontal averaging kernels reveals that for both gases the horizontal resolution is sampling-limited, i.e., information is not smeared over consecutive limb scans. Zonal mean seasonal composites of both CH4 and N2O exhibit the typical distribution of source gases with strong upwelling in the tropics and subsidence above the winter poles. Comparison with the previous data version shows several improvements: First, the vertical resolution of the retrieved CH4 (N2O) profiles has generally been significantly enhanced and varies between 2.5 (2.5) and 4 (5) km at altitudes between 10 and 60 km, with the best resolution around 30 km for both species. Secondly, the number of not converged retrievals has been clearly reduced, and thirdly, formerly strongly oscillating profiles are now considerably smoother. [ABSTRACT FROM AUTHOR]

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 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 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 of 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 5K to 50K with a systematic component of around 10 K, the latter being dominated by 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 NLRMSIS2.0 model by 30K to 80K in the 100-120 km region, and are colder above. [ABSTRACT FROM AUTHOR]

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 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. [ABSTRACT FROM AUTHOR]