Except for a few reactions involving electronically excited molecular or atomic oxygen or nitroge... more Except for a few reactions involving electronically excited molecular or atomic oxygen or nitrogen, atmospheric chemistry modelling usually assumes that the temperature dependence of reaction rates is characterized by Arrhenius' law involving kinetic temperatures. It is known, however, that in the upper atmosphere the vibrational temperatures may exceed the kinetic temperatures by several hundreds of Kelvins. This excess energy has an impact on the reaction rates. We have used upper atmospheric OH populations and reaction rate coefficients for OH(v=0...9)+O3 and OH(v=0...9)+O to estimate the effective (i.e. population weighted) reaction rates for various atmospheric conditions. We have found that the effective rate coefficient for OH(v=0...9)+O3 can be larger by a factor of up to 1470 than that involving OH in its vibrational ground state only. At altitudes where vibrationally excited states of OH are highly populated, the OH reaction is a minor sink of Ox and O3 compared to other reactions involving, e.g., atomic oxygen. Thus the impact of vibrationally excited OH on the ozone or Ox sink remains small. Among quiescent atmospheres under investigation, the largest while still small (less than 0.1%) effect was found for the polar winter upper stratosphere and mesosphere. The contribution of the reaction of vibrationally excited OH with ozone to the OH sink is largest in the upper polar winter stratosphere (up to 4%), while its effect on the HO2 source is larger in the lower thermosphere (up to 1.5% for polar winter and 2.5% for midlatitude night conditions). For OH(v=0...9)+O the effective rate coefficients are lower by up to 11% than those involving OH in its vibrational ground state. The effects on the odd oxygen sink are negative and can reach −3% (midlatitudinal nighttime lowermost thermosphere), i.e. neglecting vibrational excitation overestimates the odd oxygen sink. The OH sink is overestimated by up to 10%. After a solar proton event, when upper atmospheric OH can be enhanced by an order of magnitude, the excess relative odd oxygen sink by consideration of vibrational excitation in the reaction of OH(v=0...9)+O3 is estimated at up to 0.2%, and the OH sink by OH(v=0...9)+O can be reduced by 12% in the thermosphere by vibrational excitation.
1] A multimodel assessment of the performance of chemistry-climate models (CCMs) in the extratrop... more 1] A multimodel assessment of the performance of chemistry-climate models (CCMs) in the extratropical upper troposphere/lower stratosphere (UTLS) is conducted for the first time. Process-oriented diagnostics are used to validate dynamical and transport characteristics of 18 CCMs using meteorological analyses and aircraft and satellite observations. The main dynamical and chemical climatological characteristics of the extratropical UTLS are generally well represented by the models, despite the limited horizontal and vertical resolution. The seasonal cycle of lowermost stratospheric mass is realistic, however with a wide spread in its mean value. A tropopause inversion layer is present in most models, although the maximum in static stability is located too high above the tropopause and is somewhat too weak, as expected from limited model resolution. Similar comments apply to the extratropical tropopause transition layer. The seasonality in lower stratospheric chemical tracers is consistent with the seasonality in the Brewer-Dobson circulation. Both vertical and meridional tracer gradients are of similar strength to those found in observations. Models that perform less well tend to use a semi-Lagrangian transport scheme and/or have a very low resolution. Two models, and the multimodel mean, score consistently well on all diagnostics, while seven other models score well on all diagnostics except the seasonal cycle of water vapor. Only four of the models are consistently below average. The lack of tropospheric chemistry in most models limits their evaluation in the upper troposphere. Finally, the UTLS is relatively sparsely sampled by observations, limiting our ability to quantitatively evaluate many aspects of model performance.
Satellite observations show that the enormous solar proton events (SPEs) in October-November 2003... more Satellite observations show that the enormous solar proton events (SPEs) in October-November 2003 had significant effects on the composition of the stratosphere and mesosphere in the polar regions. After the October-November 2003 SPEs and in early 2004 significant enhancements of NO x (=NO+NO 2 ) in the upper stratosphere 5 and lower mesosphere in the Northern Hemisphere were observed by several satellite instruments. Here we present global full chemistry calculations performed with the CLaMS model to study the impact of mesospheric NO x intrusions on Arctic polar ozone loss processes in the stratosphere. Several model simulations are preformed with different upper boundary conditions for NO x at 2000 K potential temperature (≈50 km 10 altitude). In our study we focus on the impact of the non-local production of NO x which means the downward transport of enhanced NO x from the mesosphere in the stratosphere. The local production of NO x in the stratosphere is neglected. Our findings show that intrusions of mesospheric air into the stratosphere, transporting high burdens of NO x , affect the composition of the Arctic polar region down to about 400 K 15 (≈17 -18 km). We compare our simulated NO x and O 3 mixing ratios with satellite observations by ACE-FTS and MIPAS processed at IMK/IAA and derive an upper limit for the ozone loss caused by enhanced mesospheric NO x . Our findings show that in the Arctic polar vortex (Equivalent Lat.> 70 • N) the accumulated column ozone loss between 350 -2000 K potential temperature (≈14 -50 km altitude) caused by the SPEs
The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is a high-resolution limb s... more 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 ffir Meteorologic 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 pm MIPAS radiances. The fundamental to-vibrational band of nitric oxide emitting at 5.3 pm 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.
The Michelson Interferometer for Passive Atmosphere Sounding (MIPAS) onboard the polar orbiter EN... more The Michelson Interferometer for Passive Atmosphere Sounding (MIPAS) onboard the polar orbiter ENVISAT, successfully launched on March 1st, 2002, is a high resolution mid-IR limb sounder, designed to infer temperature and chemical composition of the stratosphere. While the standard measurements cover tangent altitudes from 6 to 70 km, special observations, taken from time to time, scan the atmosphere up to
Remote Sensing of Clouds and the Atmosphere VII, 2003
On 1 March 2002 the Envisat research satellite has been launched successfully into its sun-synchr... more On 1 March 2002 the Envisat research satellite has been launched successfully into its sun-synchronous orbit. One of its instruments for atmospheric composition sounding is the Michelson Interferometer for Passive Atmospheric Sounding, a limb-scanning mid-infrared Fourier transform spectrometer. Different scientific objectives of data users require different approaches to data analysis, which are discussed. A strategy on how to validate the
Remote Sensing of Clouds and the Atmosphere VIII, 2004
MIPAS on ENVISAT measures vertical profiles of atmospheric temperature, ozone, and other species ... more MIPAS on ENVISAT measures vertical profiles of atmospheric temperature, ozone, and other species with nearly global coverage and high accuracy/precision. The standard observation mode covers the altitude region between 6 and 68 km. The atmospheric state parameters retrieved from MIPAS measurements using the IMK data analysis processor are compared with a number of other satellite observations. Our comparisons in this
The Michelson Interferometer for Passive Atmosphere Sounding (MIPAS) on board of ESA's ENVISA... more The Michelson Interferometer for Passive Atmosphere Sounding (MIPAS) on board of ESA's ENVISAT measures the global distribution of infrared emissions by atmospheric gases from 4mum to 15mum. The upper atmosphere measurement mode spans altitudes from 20-100 km and allows for the retrieval of species from the tropopause region up to the lower thermosphere. For the modelling of the infrared radiances
We present the Karlsruhe Optimized and Precise Radiative transfer Algorithm (KOPRA) which has bee... more We present the Karlsruhe Optimized and Precise Radiative transfer Algorithm (KOPRA) which has been specifically developed for data analysis of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) going to be launched on ESA's polar-orbiting Environmental Satellite 1 in 1999. KOPRA has been designed to account for the particular instrument requirements of MIPAS and the observation scenarii during the ENVISAT
Stratospheric and upper tropospheric distributions of peroxynitric acid (HO2NO2) were retrieved f... more Stratospheric and upper tropospheric distributions of peroxynitric acid (HO2NO2) were retrieved from limb infrared spectral measurements of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board the Environmental Satellite (ENVISAT). Single-profile precisions are estimated at 6-14 parts per trillion by volume (pptv) in the altitude range 7-17 km and 19-34 pptv from 17 to 42 km. The vertical resolution
1] We present water vapor profiles obtained from infrared limb emission measurements recorded by ... more 1] We present water vapor profiles obtained from infrared limb emission measurements recorded by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board the European Environmental Satellite (Envisat). These retrievals are based on constrained nonlinear least squares fitting. The retrievals are very sensitive to the radiative signals of thin transparent clouds and measurements showing any signature of cloud contamination have been rigorously excluded. The vertical resolution of the retrieved water vapor profiles is 4.5 to 6.5 km up to an altitude of approximately 42 km. The resulting total error of the retrieved water vapor profiles, including measurement noise, systematic and random parameter uncertainties like interfering species or preretrieved temperature or spectroscopic data, is in the range of 6 to 9% in the stratosphere. Towards the tropopause, the error increases up to 30% due to the exponential gradient of the tropospheric water vapor profile, where small line of sight uncertainties lead to strong absolute variations in the water vapor profile below the hygropause. Averaged water vapor distributions obtained from measurements taken during 11 days in June, July, and August 2003 show the expected distributions with low water vapor volume mixing ratios (VMRs) above the tropopause, comparatively dry air inside the tropical stratospheric updraft region and indications for strong dehydration above the Antarctic continent inside the polar vortex. Additionally, in the transition from tropics to subtropics, a latitude band was observed where, in higher altitudes, large water vapor VMRs were measured compared to adjacent tropical and midlatitudinal regions. Especially over the Arabic peninsula, a moist region at 18 km altitude was observed, which was probably related to the South Asian monsoon circulation.
Past studies have shown that a clear relationship exists between the field of a passive tracer an... more Past studies have shown that a clear relationship exists between the field of a passive tracer and the Probability Distribution Function (PDF) of tracer concentrations, which can be exploited to identify the position and variability of stratospheric barriers to isentropic mixing.
We present a climatology of monthly and 10 • zonal mean profiles of sulfur dioxide (SO 2 ) volume... more We present a climatology of monthly and 10 • zonal mean profiles of sulfur dioxide (SO 2 ) volume mixing ratios (vmr) derived from MIPAS/Envisat measurements in the altitude range 15-45 km from July 2002 until April 2012. The vertical resolution varies from 3.5-4 km in the lower stratosphere up to 6-10 km at the upper end of the profiles, with estimated total errors of 5-20 pptv for single profiles of SO 2 . Comparisons with the few available observations of SO 2 up to high altitudes from ATMOS for a volcanically perturbed situation from ACE-FTS and, at the lowest altitudes, with stratospheric in situ observations reveal general consistency of the datasets. The observations are the first empirical confirmation of features of the stratospheric SO 2 distribution, which have only been shown by models up to now: (1) the local maximum of SO 2 at around 25-30 km altitude, which is explained by the conversion of carbonyl sulfide (COS) as the precursor of the Junge layer; and (2) the downwelling of SO 2 -rich air to altitudes of 25-30 km at high latitudes during winter and its subsequent depletion on availability of sunlight. This has been proposed as the reason for the sudden appearance of enhanced concentrations of condensation nuclei during Arctic and Antarctic spring. Further, the strong increase of SO 2 to values of 80-100 pptv in the upper stratosphere through photolysis of H 2 SO 4 has been confirmed. Lower stratospheric variability of SO 2 could mainly be explained by volcanic activity, and no hints of a strong anthropogenic influence have been found. Regression analysis revealed a QBO (quasi-biennial oscillation) signal of the SO 2 time series in the tropics at about 30-35 km, an SAO (semi-annual oscillation) signal at tropical and subtropical latitudes above 32 km and annual periodics predominantly at high latitudes. Further, the analysis indicates a correlation with the solar cycle in the tropics and southern subtropics above 30 km. Significant negative linear trends are found in the tropical lower stratosphere, probably due to reduced tropical volcanic activity and at southern mid-latitudes above 35 km. A positive trend is visible in the lower and middle stratosphere at polar to subtropical southern latitudes.
We have used high spectral resolution spectroscopic measurements from the MIPAS instrument on the... more We have used high spectral resolution spectroscopic measurements from the MIPAS instrument on the Envisat satellite to simultaneously retrieve vertical profiles of H 2 O and HDO in the stratosphere and uppermost troposphere. Variations in the deuterium content of water are expressed in the common δ notation, where δD is the deviation of the Deuterium/Hydrogen ratio in a sample from a standard isotope ratio. A thorough error analysis of the retrievals confirms that reliable δD data can be obtained up to an altitude of ∼45 km. Averaging over multiple orbits and thus over longitudes further reduces the random part of the error. The absolute total error of averaged δD is between 36‰ and 111‰. With values lower than 42‰ the total random error is significantly smaller than the natural variability of δD. The data compare well with previous investigations. The MIPAS measurements now provide a unique global data set of highquality δD data that will provide novel insight into the stratospheric water cycle.
Remote Sensing of Clouds and the Atmosphere Vii, 2003
On March 1, 2002 the space-borne limb viewing mid-infrared high-resolution Michelson Interferomet... more On March 1, 2002 the space-borne limb viewing mid-infrared high-resolution Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) has been brought on board the ENVISAT satellite into a polar sun-synchroneous orbit. Although the level-1 testing and validation phase ...
Optical Remote Sensing of the Atmosphere and Clouds III, 2003
Spectral limb radiances measured by the Michelson Interferometer for Passive Atmospheric Sounding... more Spectral limb radiances measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard the Envisat Environmental research satellite are characterized in terms of instrument line shape (ILS), noise equivalent spectral radiance (NESR) and possible impact of non-local thermodynamic equilibrium emission in deep space calibration spectra. Furthermore, it is assessed if the operational processing baseline to set the top of
Measurements of thermal emission in the mid-infrared by Envisat/MIPAS allow the retrieval of HDO ... more Measurements of thermal emission in the mid-infrared by Envisat/MIPAS allow the retrieval of HDO information roughly in the altitude range between 10 km and 50 km. From September 2002 to March 2004 MIPAS performed measurements in the full spectral mode. To assess the quality of the HDO data set obtained during that period compar-5 isons with measurements by Odin/SMR and SCISAT/ACE-FTS were performed. Comparisons were made on profile-to-profile basis as well as using seasonal and monthly means. All in all the comparisons yield favourable results. The largest deviations between MIPAS and ACE-FTS are observed below 15 km, where relative deviations can occasionally exceed 100%. Despite that the latitudinal structures observed by both 10 instruments fit. Between 15 km and 20 km there is less consistency, especially in the Antarctic during winter and spring. Above 20 km there is a high consistency in the structures observed by all three instruments. MIPAS and ACE-FTS typically agree within 10%, with MIPAS mostly showing higher abundances than ACE-FTS. Both data sets show considerably more HDO than SMR. This bias can mostly be explained by un-15 certainties in spectroscopic parameters. Above 40 km, where the MIPAS HDO retrieval reaches its limits, still good agreement with the structures observed by SMR is found for most seasons. This puts some confidence in the MIPAS data at these altitudes.
Except for a few reactions involving electronically excited molecular or atomic oxygen or nitroge... more Except for a few reactions involving electronically excited molecular or atomic oxygen or nitrogen, atmospheric chemistry modelling usually assumes that the temperature dependence of reaction rates is characterized by Arrhenius' law involving kinetic temperatures. It is known, however, that in the upper atmosphere the vibrational temperatures may exceed the kinetic temperatures by several hundreds of Kelvins. This excess energy has an impact on the reaction rates. We have used upper atmospheric OH populations and reaction rate coefficients for OH(v=0...9)+O3 and OH(v=0...9)+O to estimate the effective (i.e. population weighted) reaction rates for various atmospheric conditions. We have found that the effective rate coefficient for OH(v=0...9)+O3 can be larger by a factor of up to 1470 than that involving OH in its vibrational ground state only. At altitudes where vibrationally excited states of OH are highly populated, the OH reaction is a minor sink of Ox and O3 compared to other reactions involving, e.g., atomic oxygen. Thus the impact of vibrationally excited OH on the ozone or Ox sink remains small. Among quiescent atmospheres under investigation, the largest while still small (less than 0.1%) effect was found for the polar winter upper stratosphere and mesosphere. The contribution of the reaction of vibrationally excited OH with ozone to the OH sink is largest in the upper polar winter stratosphere (up to 4%), while its effect on the HO2 source is larger in the lower thermosphere (up to 1.5% for polar winter and 2.5% for midlatitude night conditions). For OH(v=0...9)+O the effective rate coefficients are lower by up to 11% than those involving OH in its vibrational ground state. The effects on the odd oxygen sink are negative and can reach −3% (midlatitudinal nighttime lowermost thermosphere), i.e. neglecting vibrational excitation overestimates the odd oxygen sink. The OH sink is overestimated by up to 10%. After a solar proton event, when upper atmospheric OH can be enhanced by an order of magnitude, the excess relative odd oxygen sink by consideration of vibrational excitation in the reaction of OH(v=0...9)+O3 is estimated at up to 0.2%, and the OH sink by OH(v=0...9)+O can be reduced by 12% in the thermosphere by vibrational excitation.
1] A multimodel assessment of the performance of chemistry-climate models (CCMs) in the extratrop... more 1] A multimodel assessment of the performance of chemistry-climate models (CCMs) in the extratropical upper troposphere/lower stratosphere (UTLS) is conducted for the first time. Process-oriented diagnostics are used to validate dynamical and transport characteristics of 18 CCMs using meteorological analyses and aircraft and satellite observations. The main dynamical and chemical climatological characteristics of the extratropical UTLS are generally well represented by the models, despite the limited horizontal and vertical resolution. The seasonal cycle of lowermost stratospheric mass is realistic, however with a wide spread in its mean value. A tropopause inversion layer is present in most models, although the maximum in static stability is located too high above the tropopause and is somewhat too weak, as expected from limited model resolution. Similar comments apply to the extratropical tropopause transition layer. The seasonality in lower stratospheric chemical tracers is consistent with the seasonality in the Brewer-Dobson circulation. Both vertical and meridional tracer gradients are of similar strength to those found in observations. Models that perform less well tend to use a semi-Lagrangian transport scheme and/or have a very low resolution. Two models, and the multimodel mean, score consistently well on all diagnostics, while seven other models score well on all diagnostics except the seasonal cycle of water vapor. Only four of the models are consistently below average. The lack of tropospheric chemistry in most models limits their evaluation in the upper troposphere. Finally, the UTLS is relatively sparsely sampled by observations, limiting our ability to quantitatively evaluate many aspects of model performance.
Satellite observations show that the enormous solar proton events (SPEs) in October-November 2003... more Satellite observations show that the enormous solar proton events (SPEs) in October-November 2003 had significant effects on the composition of the stratosphere and mesosphere in the polar regions. After the October-November 2003 SPEs and in early 2004 significant enhancements of NO x (=NO+NO 2 ) in the upper stratosphere 5 and lower mesosphere in the Northern Hemisphere were observed by several satellite instruments. Here we present global full chemistry calculations performed with the CLaMS model to study the impact of mesospheric NO x intrusions on Arctic polar ozone loss processes in the stratosphere. Several model simulations are preformed with different upper boundary conditions for NO x at 2000 K potential temperature (≈50 km 10 altitude). In our study we focus on the impact of the non-local production of NO x which means the downward transport of enhanced NO x from the mesosphere in the stratosphere. The local production of NO x in the stratosphere is neglected. Our findings show that intrusions of mesospheric air into the stratosphere, transporting high burdens of NO x , affect the composition of the Arctic polar region down to about 400 K 15 (≈17 -18 km). We compare our simulated NO x and O 3 mixing ratios with satellite observations by ACE-FTS and MIPAS processed at IMK/IAA and derive an upper limit for the ozone loss caused by enhanced mesospheric NO x . Our findings show that in the Arctic polar vortex (Equivalent Lat.> 70 • N) the accumulated column ozone loss between 350 -2000 K potential temperature (≈14 -50 km altitude) caused by the SPEs
The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is a high-resolution limb s... more 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 ffir Meteorologic 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 pm MIPAS radiances. The fundamental to-vibrational band of nitric oxide emitting at 5.3 pm 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.
The Michelson Interferometer for Passive Atmosphere Sounding (MIPAS) onboard the polar orbiter EN... more The Michelson Interferometer for Passive Atmosphere Sounding (MIPAS) onboard the polar orbiter ENVISAT, successfully launched on March 1st, 2002, is a high resolution mid-IR limb sounder, designed to infer temperature and chemical composition of the stratosphere. While the standard measurements cover tangent altitudes from 6 to 70 km, special observations, taken from time to time, scan the atmosphere up to
Remote Sensing of Clouds and the Atmosphere VII, 2003
On 1 March 2002 the Envisat research satellite has been launched successfully into its sun-synchr... more On 1 March 2002 the Envisat research satellite has been launched successfully into its sun-synchronous orbit. One of its instruments for atmospheric composition sounding is the Michelson Interferometer for Passive Atmospheric Sounding, a limb-scanning mid-infrared Fourier transform spectrometer. Different scientific objectives of data users require different approaches to data analysis, which are discussed. A strategy on how to validate the
Remote Sensing of Clouds and the Atmosphere VIII, 2004
MIPAS on ENVISAT measures vertical profiles of atmospheric temperature, ozone, and other species ... more MIPAS on ENVISAT measures vertical profiles of atmospheric temperature, ozone, and other species with nearly global coverage and high accuracy/precision. The standard observation mode covers the altitude region between 6 and 68 km. The atmospheric state parameters retrieved from MIPAS measurements using the IMK data analysis processor are compared with a number of other satellite observations. Our comparisons in this
The Michelson Interferometer for Passive Atmosphere Sounding (MIPAS) on board of ESA's ENVISA... more The Michelson Interferometer for Passive Atmosphere Sounding (MIPAS) on board of ESA's ENVISAT measures the global distribution of infrared emissions by atmospheric gases from 4mum to 15mum. The upper atmosphere measurement mode spans altitudes from 20-100 km and allows for the retrieval of species from the tropopause region up to the lower thermosphere. For the modelling of the infrared radiances
We present the Karlsruhe Optimized and Precise Radiative transfer Algorithm (KOPRA) which has bee... more We present the Karlsruhe Optimized and Precise Radiative transfer Algorithm (KOPRA) which has been specifically developed for data analysis of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) going to be launched on ESA's polar-orbiting Environmental Satellite 1 in 1999. KOPRA has been designed to account for the particular instrument requirements of MIPAS and the observation scenarii during the ENVISAT
Stratospheric and upper tropospheric distributions of peroxynitric acid (HO2NO2) were retrieved f... more Stratospheric and upper tropospheric distributions of peroxynitric acid (HO2NO2) were retrieved from limb infrared spectral measurements of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board the Environmental Satellite (ENVISAT). Single-profile precisions are estimated at 6-14 parts per trillion by volume (pptv) in the altitude range 7-17 km and 19-34 pptv from 17 to 42 km. The vertical resolution
1] We present water vapor profiles obtained from infrared limb emission measurements recorded by ... more 1] We present water vapor profiles obtained from infrared limb emission measurements recorded by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on board the European Environmental Satellite (Envisat). These retrievals are based on constrained nonlinear least squares fitting. The retrievals are very sensitive to the radiative signals of thin transparent clouds and measurements showing any signature of cloud contamination have been rigorously excluded. The vertical resolution of the retrieved water vapor profiles is 4.5 to 6.5 km up to an altitude of approximately 42 km. The resulting total error of the retrieved water vapor profiles, including measurement noise, systematic and random parameter uncertainties like interfering species or preretrieved temperature or spectroscopic data, is in the range of 6 to 9% in the stratosphere. Towards the tropopause, the error increases up to 30% due to the exponential gradient of the tropospheric water vapor profile, where small line of sight uncertainties lead to strong absolute variations in the water vapor profile below the hygropause. Averaged water vapor distributions obtained from measurements taken during 11 days in June, July, and August 2003 show the expected distributions with low water vapor volume mixing ratios (VMRs) above the tropopause, comparatively dry air inside the tropical stratospheric updraft region and indications for strong dehydration above the Antarctic continent inside the polar vortex. Additionally, in the transition from tropics to subtropics, a latitude band was observed where, in higher altitudes, large water vapor VMRs were measured compared to adjacent tropical and midlatitudinal regions. Especially over the Arabic peninsula, a moist region at 18 km altitude was observed, which was probably related to the South Asian monsoon circulation.
Past studies have shown that a clear relationship exists between the field of a passive tracer an... more Past studies have shown that a clear relationship exists between the field of a passive tracer and the Probability Distribution Function (PDF) of tracer concentrations, which can be exploited to identify the position and variability of stratospheric barriers to isentropic mixing.
We present a climatology of monthly and 10 • zonal mean profiles of sulfur dioxide (SO 2 ) volume... more We present a climatology of monthly and 10 • zonal mean profiles of sulfur dioxide (SO 2 ) volume mixing ratios (vmr) derived from MIPAS/Envisat measurements in the altitude range 15-45 km from July 2002 until April 2012. The vertical resolution varies from 3.5-4 km in the lower stratosphere up to 6-10 km at the upper end of the profiles, with estimated total errors of 5-20 pptv for single profiles of SO 2 . Comparisons with the few available observations of SO 2 up to high altitudes from ATMOS for a volcanically perturbed situation from ACE-FTS and, at the lowest altitudes, with stratospheric in situ observations reveal general consistency of the datasets. The observations are the first empirical confirmation of features of the stratospheric SO 2 distribution, which have only been shown by models up to now: (1) the local maximum of SO 2 at around 25-30 km altitude, which is explained by the conversion of carbonyl sulfide (COS) as the precursor of the Junge layer; and (2) the downwelling of SO 2 -rich air to altitudes of 25-30 km at high latitudes during winter and its subsequent depletion on availability of sunlight. This has been proposed as the reason for the sudden appearance of enhanced concentrations of condensation nuclei during Arctic and Antarctic spring. Further, the strong increase of SO 2 to values of 80-100 pptv in the upper stratosphere through photolysis of H 2 SO 4 has been confirmed. Lower stratospheric variability of SO 2 could mainly be explained by volcanic activity, and no hints of a strong anthropogenic influence have been found. Regression analysis revealed a QBO (quasi-biennial oscillation) signal of the SO 2 time series in the tropics at about 30-35 km, an SAO (semi-annual oscillation) signal at tropical and subtropical latitudes above 32 km and annual periodics predominantly at high latitudes. Further, the analysis indicates a correlation with the solar cycle in the tropics and southern subtropics above 30 km. Significant negative linear trends are found in the tropical lower stratosphere, probably due to reduced tropical volcanic activity and at southern mid-latitudes above 35 km. A positive trend is visible in the lower and middle stratosphere at polar to subtropical southern latitudes.
We have used high spectral resolution spectroscopic measurements from the MIPAS instrument on the... more We have used high spectral resolution spectroscopic measurements from the MIPAS instrument on the Envisat satellite to simultaneously retrieve vertical profiles of H 2 O and HDO in the stratosphere and uppermost troposphere. Variations in the deuterium content of water are expressed in the common δ notation, where δD is the deviation of the Deuterium/Hydrogen ratio in a sample from a standard isotope ratio. A thorough error analysis of the retrievals confirms that reliable δD data can be obtained up to an altitude of ∼45 km. Averaging over multiple orbits and thus over longitudes further reduces the random part of the error. The absolute total error of averaged δD is between 36‰ and 111‰. With values lower than 42‰ the total random error is significantly smaller than the natural variability of δD. The data compare well with previous investigations. The MIPAS measurements now provide a unique global data set of highquality δD data that will provide novel insight into the stratospheric water cycle.
Remote Sensing of Clouds and the Atmosphere Vii, 2003
On March 1, 2002 the space-borne limb viewing mid-infrared high-resolution Michelson Interferomet... more On March 1, 2002 the space-borne limb viewing mid-infrared high-resolution Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) has been brought on board the ENVISAT satellite into a polar sun-synchroneous orbit. Although the level-1 testing and validation phase ...
Optical Remote Sensing of the Atmosphere and Clouds III, 2003
Spectral limb radiances measured by the Michelson Interferometer for Passive Atmospheric Sounding... more Spectral limb radiances measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard the Envisat Environmental research satellite are characterized in terms of instrument line shape (ILS), noise equivalent spectral radiance (NESR) and possible impact of non-local thermodynamic equilibrium emission in deep space calibration spectra. Furthermore, it is assessed if the operational processing baseline to set the top of
Measurements of thermal emission in the mid-infrared by Envisat/MIPAS allow the retrieval of HDO ... more Measurements of thermal emission in the mid-infrared by Envisat/MIPAS allow the retrieval of HDO information roughly in the altitude range between 10 km and 50 km. From September 2002 to March 2004 MIPAS performed measurements in the full spectral mode. To assess the quality of the HDO data set obtained during that period compar-5 isons with measurements by Odin/SMR and SCISAT/ACE-FTS were performed. Comparisons were made on profile-to-profile basis as well as using seasonal and monthly means. All in all the comparisons yield favourable results. The largest deviations between MIPAS and ACE-FTS are observed below 15 km, where relative deviations can occasionally exceed 100%. Despite that the latitudinal structures observed by both 10 instruments fit. Between 15 km and 20 km there is less consistency, especially in the Antarctic during winter and spring. Above 20 km there is a high consistency in the structures observed by all three instruments. MIPAS and ACE-FTS typically agree within 10%, with MIPAS mostly showing higher abundances than ACE-FTS. Both data sets show considerably more HDO than SMR. This bias can mostly be explained by un-15 certainties in spectroscopic parameters. Above 40 km, where the MIPAS HDO retrieval reaches its limits, still good agreement with the structures observed by SMR is found for most seasons. This puts some confidence in the MIPAS data at these altitudes.
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