The Experts below are selected from a list of 7551 Experts worldwide ranked by ideXlab platform

T Von Clarmann - One of the best experts on this subject based on the ideXlab platform.

  • global cfc 11 ccl 3 f and cfc 12 ccl 2 f 2 measurements with the michelson interferometer for passive Atmospheric Sounding mipas retrieval climatologies and trends
    Atmospheric Chemistry and Physics, 2012
    Co-Authors: Sylvia Kellmann, Michael Höpfner, B Funke, N Glatthor, T Von Clarmann, M Kiefer, G P Stiller, E Eckert, J Orphal, U Grabowski
    Abstract:

    Abstract. Vertical profiles of CFC-11 (CCl 3 F) and CFC-12 (CCl 2 F 2 ) have been measured with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) with global coverage under daytime and nighttime conditions. The profile retrieval is based on constrained nonlinear least squares fitting of measured limb spectral radiance to modeled spectra. CFC-11 is measured in its ν 4 -band at 850 cm −1 , and CFC-12 is analyzed in its ν 6 -band at 922 cm −1 . To stabilize the retrievals, a Tikhonov-type smoothing constraint is applied. Main retrieval error sources are measurement noise and elevation pointing uncertainties. The estimated CFC-11 retrieval errors including noise and parameter errors but excluding spectroscopic data uncertainties are below 10 pptv in the middle stratosphere, depending on altitude, the MIPAS measurement mode and the actual Atmospheric situation. For CFC-12 the total retrieval errors are below 28 pptv at an altitude resolution varying from 3 to 5 km. Time series of altitude/latitude bins were fitted by a simple parametric approach including constant and linear terms, a quasi-biennial oscillation (QBO) proxy and sine and cosine terms of several periods. In the time series from 2002 to 2011, quasi-biennial and annual oscillations are clearly visible. A decrease of stratospheric CFC mixing ratios in response to the Montreal Protocol is observed for most altitudes and latitudes. However, the trends differ from the trends measured in the troposphere, they are even positive at some latitudes and altitudes, and can in some cases only be explained by decadal changes in Atmospheric age of air spectra or vertical mixing patterns.

  • hocl chemistry in the antarctic stratospheric vortex 2002 as observed with the michelson interferometer for passive Atmospheric Sounding mipas
    Atmospheric Chemistry and Physics, 2008
    Co-Authors: Sylvia Kellmann, Michael Höpfner, N Glatthor, T Von Clarmann, G P Stiller, R Ruhnke, Oliver Kirner, T Reddmann, W Kouker
    Abstract:

    Abstract. In the 2002 Antarctic polar vortex enhanced HOCl mixing ratios were detected by the Michelson Interferometer for Passive Atmospheric Sounding both at altitudes of around 35 km (1000 K potential temperature), where HOCl abundances are ruled by gas phase chemistry and at around 18–24 km (475–625 K), which belongs to the altitude domain where heterogeneous chlorine chemistry is relevant. At altitudes of 33 to 40 km polar vortex HOCl mixing ratios were found to be around 0.14 ppbv as long as the polar vortex was intact, centered at the pole, and thus received relatively little sunlight. This is the altitude region where in midlatitudinal and tropic atmospheres peak HOCl mixing ratios significantly above 0.2 ppbv (in terms of daily mean values) are observed. After deformation and displacement of the polar vortex in the course of a major warming, ClO-rich vortex air was more exposed to sunlight, where enhanced HOx abundances led to largely increased HOCl mixing ratios (up to 0.3 ppbv), exceeding typical midlatitudinal and tropical amounts significantly. The HOCl increase was preceded by an increase of ClO. Model runs could reproduce these measurements only when the Stimpfle et al. (1979) rate constant for the reaction ClO+HO2→HOCl+O2 was used but not with the current JPL recommendation. At an altitude of 24 km, HOCl mixing ratios of up to 0.15 ppbv were detected. This HOCl enhancement, which is already visible in 18 September data, is attributed to heterogeneous chemistry, which is in agreement with observations of polar stratospheric clouds. The measurements were compared to a model run where no polar stratospheric clouds appeared during the observation period. The fact that HOCl still was produced in the model run suggests that a significant part of HOCl was generated from ClO rather than directly via heterogeneous reaction. Excess ClO, lower ClONO2 and earlier loss of HOCl in the measurements are attributed to ongoing heterogeneous chemistry which is not reproduced by the model. On 11 October, polar vortex mean daytime mixing ratios were only 0.03 ppbv.

  • analysis of nonlocal thermodynamic equilibrium co 4 7 μm fundamental isotopic and hot band emissions measured by the michelson interferometer for passive Atmospheric Sounding on envisat
    Journal of Geophysical Research, 2007
    Co-Authors: B Funke, Michael Höpfner, M Lopezpuertas, T Von Clarmann, U Grabowski, D Bermejopantaleon, G P Stiller, M Kaufmann
    Abstract:

    [1] Nonlocal thermodynamic equilibrium (non-LTE) simulations of the 12C16O(1 → 0) fundamental band, the 12C16O(2 → 1) hot band, and the isotopic 13C16O(1 → 0) band performed with the Generic Radiative Transfer and non-LTE population Algorithm (GRANADA) and the Karlsruhe Optimized and Precise Radiative Transfer Algorithm (KOPRA) have been compared to spectrally resolved 4.7 μm radiances measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). The performance of the non-LTE simulation has been assessed in terms of band radiance ratios in order to avoid a compensation of possible non-LTE model errors by retrieval errors in the CO abundances inferred from MIPAS data with the same non-LTE algorithms. The agreement with the measurements is within 5% for the fundamental band and within 10% for the hot band. Simulated 13C16O radiances agree with the measurements within the instrumental noise error. Solar reflectance at the surface or clouds has been identified as an important additional excitation mechanism for the CO(2) state. The study represents a thorough validation of the non-LTE scheme used in the retrieval of CO abundances from MIPAS data.

  • global peroxyacetyl nitrate pan retrieval in the upper troposphere from limb emission spectra of the michelson interferometer for passive Atmospheric Sounding mipas
    Atmospheric Chemistry and Physics, 2007
    Co-Authors: N Glatthor, Sylvia Kellmann, Michael Höpfner, B Funke, T Von Clarmann, H Fischer, U Grabowski, M Kiefer, A Linden, Mathias Milz
    Abstract:

    We use limb emission spectra of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard the ENVIronmental SATellite (ENVISAT) to derive the first global distribution of peroxyacetyl nitrate (PAN) in the upper troposphere. PAN is generated in tropospheric air masses polluted by fuel combustion or biomass burning and acts as a reservoir and carrier of NOx in the cold free tropo- sphere. PAN exhibits continuum-like broadband structures in the mid-infrared region and was retrieved in a contigu- ous analysis window covering the wavenumber region 775- 800 cm 1 . The interfering species CCl4, HCFC-22, H2O, ClONO2, CH3CCl3 and C2H2 were fitted along with PAN, whereas pre-fitted profiles were used to model the contri- bution of other contaminants like ozone. Sensitivity tests consisting in retrieval without consideration of PAN demon- strated the existence of PAN signatures in MIPAS spectra ob- tained in polluted air masses. The analysed dataset consists of 10 days between 4 October and 1 December 2003. This period covers the end of the biomass burning season in South America and South and East Africa, in which generally large amounts of pollutants are produced and distributed over wide areas of the southern hemispheric free troposphere. Indeed, elevated PAN amounts of 200-700 pptv were measured in a large plume extending from Brasil over the Southern At- lantic, Central and South Africa, the South Indian Ocean as far as Australia at altitudes between 8 and 16 km. Enhanced PAN values were also found in a much more restricted area between northern subtropical Africa and India. The most sig- nificant northern midlatitude PAN signal was detected in an area at 8 km altitude extending from China into the Chinese Sea. The average mid and high latitude PAN amounts found at 8 km were around 125 pptv in the northern, but only be- tween 50 and 75 pptv in the southern hemisphere. The PAN distribution found in the southern hemispheric tropics and subtropics is highly correlated with the jointly fitted acety- lene (C2H2), which is another pollutant produced by biomass burning, and agrees reasonably well with the CO plume de- tected during end of September 2003 at the 275 hPa level ( 10 km) by the Measurement of Pollution in the Tropo- sphere (MOPITT) instrument on the Terra satellite. Simi- lar southern hemispheric PAN amounts were also observed by previous airborne measurements performed in Septem- ber/October 1992 and 1996 above the South Atlantic and the South Pacific, respectively.

  • global distributions of ho2no2 as observed by the michelson interferometer for passive Atmospheric Sounding mipas
    Journal of Geophysical Research, 2007
    Co-Authors: Gabriele Stiller, Michael Höpfner, B Funke, N Glatthor, T Von Clarmann, C Bruhl, H Fischer, U Grabowski, Patrick Jockel, Sylvia Kellmann
    Abstract:

    [1] 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 is 5 km in the upper tropospheric and stratospheric maxima. Highest stratospheric volume mixing ratios (VMRs) reaching 310 pptv at 27 km are observed at solstice conditions in subtropical latitudes and midlatitudes at the nighttime summer hemisphere, while lowest stratospheric peak VMRs as low as 38 pptv are found during polar winter near the pole. A second maximum in the upper troposphere and lower stratosphere appears from spring to the end of summer with maximum values of 80 pptv between 7 and 14 km. Retrievals based on spectroscopic line list data instead of absorption cross sections produce HO2NO2 distributions smaller by a factor of 1.5, on average. Earlier HO2NO2 measurements from balloon instruments are in good general agreement with the presented data set if the same spectroscopic data are used. Comparisons of MIPAS HO2NO2 distributions to results of the fifth-generation European Centre Hamburg general circulation model/Modular Earth Submodel System 1 (ECHAM5/MESSy1) provide agreement within 20% if near-infrared photolysis is considered. With the newly available tabulated absorption cross sections and the improved photolysis modeling, former discrepancies between HO2NO2 observations and model calculations can be considered to be largely resolved.

Michael Höpfner - One of the best experts on this subject based on the ideXlab platform.

  • global cfc 11 ccl 3 f and cfc 12 ccl 2 f 2 measurements with the michelson interferometer for passive Atmospheric Sounding mipas retrieval climatologies and trends
    Atmospheric Chemistry and Physics, 2012
    Co-Authors: Sylvia Kellmann, Michael Höpfner, B Funke, N Glatthor, T Von Clarmann, M Kiefer, G P Stiller, E Eckert, J Orphal, U Grabowski
    Abstract:

    Abstract. Vertical profiles of CFC-11 (CCl 3 F) and CFC-12 (CCl 2 F 2 ) have been measured with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) with global coverage under daytime and nighttime conditions. The profile retrieval is based on constrained nonlinear least squares fitting of measured limb spectral radiance to modeled spectra. CFC-11 is measured in its ν 4 -band at 850 cm −1 , and CFC-12 is analyzed in its ν 6 -band at 922 cm −1 . To stabilize the retrievals, a Tikhonov-type smoothing constraint is applied. Main retrieval error sources are measurement noise and elevation pointing uncertainties. The estimated CFC-11 retrieval errors including noise and parameter errors but excluding spectroscopic data uncertainties are below 10 pptv in the middle stratosphere, depending on altitude, the MIPAS measurement mode and the actual Atmospheric situation. For CFC-12 the total retrieval errors are below 28 pptv at an altitude resolution varying from 3 to 5 km. Time series of altitude/latitude bins were fitted by a simple parametric approach including constant and linear terms, a quasi-biennial oscillation (QBO) proxy and sine and cosine terms of several periods. In the time series from 2002 to 2011, quasi-biennial and annual oscillations are clearly visible. A decrease of stratospheric CFC mixing ratios in response to the Montreal Protocol is observed for most altitudes and latitudes. However, the trends differ from the trends measured in the troposphere, they are even positive at some latitudes and altitudes, and can in some cases only be explained by decadal changes in Atmospheric age of air spectra or vertical mixing patterns.

  • hocl chemistry in the antarctic stratospheric vortex 2002 as observed with the michelson interferometer for passive Atmospheric Sounding mipas
    Atmospheric Chemistry and Physics, 2008
    Co-Authors: Sylvia Kellmann, Michael Höpfner, N Glatthor, T Von Clarmann, G P Stiller, R Ruhnke, Oliver Kirner, T Reddmann, W Kouker
    Abstract:

    Abstract. In the 2002 Antarctic polar vortex enhanced HOCl mixing ratios were detected by the Michelson Interferometer for Passive Atmospheric Sounding both at altitudes of around 35 km (1000 K potential temperature), where HOCl abundances are ruled by gas phase chemistry and at around 18–24 km (475–625 K), which belongs to the altitude domain where heterogeneous chlorine chemistry is relevant. At altitudes of 33 to 40 km polar vortex HOCl mixing ratios were found to be around 0.14 ppbv as long as the polar vortex was intact, centered at the pole, and thus received relatively little sunlight. This is the altitude region where in midlatitudinal and tropic atmospheres peak HOCl mixing ratios significantly above 0.2 ppbv (in terms of daily mean values) are observed. After deformation and displacement of the polar vortex in the course of a major warming, ClO-rich vortex air was more exposed to sunlight, where enhanced HOx abundances led to largely increased HOCl mixing ratios (up to 0.3 ppbv), exceeding typical midlatitudinal and tropical amounts significantly. The HOCl increase was preceded by an increase of ClO. Model runs could reproduce these measurements only when the Stimpfle et al. (1979) rate constant for the reaction ClO+HO2→HOCl+O2 was used but not with the current JPL recommendation. At an altitude of 24 km, HOCl mixing ratios of up to 0.15 ppbv were detected. This HOCl enhancement, which is already visible in 18 September data, is attributed to heterogeneous chemistry, which is in agreement with observations of polar stratospheric clouds. The measurements were compared to a model run where no polar stratospheric clouds appeared during the observation period. The fact that HOCl still was produced in the model run suggests that a significant part of HOCl was generated from ClO rather than directly via heterogeneous reaction. Excess ClO, lower ClONO2 and earlier loss of HOCl in the measurements are attributed to ongoing heterogeneous chemistry which is not reproduced by the model. On 11 October, polar vortex mean daytime mixing ratios were only 0.03 ppbv.

  • analysis of nonlocal thermodynamic equilibrium co 4 7 μm fundamental isotopic and hot band emissions measured by the michelson interferometer for passive Atmospheric Sounding on envisat
    Journal of Geophysical Research, 2007
    Co-Authors: B Funke, Michael Höpfner, M Lopezpuertas, T Von Clarmann, U Grabowski, D Bermejopantaleon, G P Stiller, M Kaufmann
    Abstract:

    [1] Nonlocal thermodynamic equilibrium (non-LTE) simulations of the 12C16O(1 → 0) fundamental band, the 12C16O(2 → 1) hot band, and the isotopic 13C16O(1 → 0) band performed with the Generic Radiative Transfer and non-LTE population Algorithm (GRANADA) and the Karlsruhe Optimized and Precise Radiative Transfer Algorithm (KOPRA) have been compared to spectrally resolved 4.7 μm radiances measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). The performance of the non-LTE simulation has been assessed in terms of band radiance ratios in order to avoid a compensation of possible non-LTE model errors by retrieval errors in the CO abundances inferred from MIPAS data with the same non-LTE algorithms. The agreement with the measurements is within 5% for the fundamental band and within 10% for the hot band. Simulated 13C16O radiances agree with the measurements within the instrumental noise error. Solar reflectance at the surface or clouds has been identified as an important additional excitation mechanism for the CO(2) state. The study represents a thorough validation of the non-LTE scheme used in the retrieval of CO abundances from MIPAS data.

  • global peroxyacetyl nitrate pan retrieval in the upper troposphere from limb emission spectra of the michelson interferometer for passive Atmospheric Sounding mipas
    Atmospheric Chemistry and Physics, 2007
    Co-Authors: N Glatthor, Sylvia Kellmann, Michael Höpfner, B Funke, T Von Clarmann, H Fischer, U Grabowski, M Kiefer, A Linden, Mathias Milz
    Abstract:

    We use limb emission spectra of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard the ENVIronmental SATellite (ENVISAT) to derive the first global distribution of peroxyacetyl nitrate (PAN) in the upper troposphere. PAN is generated in tropospheric air masses polluted by fuel combustion or biomass burning and acts as a reservoir and carrier of NOx in the cold free tropo- sphere. PAN exhibits continuum-like broadband structures in the mid-infrared region and was retrieved in a contigu- ous analysis window covering the wavenumber region 775- 800 cm 1 . The interfering species CCl4, HCFC-22, H2O, ClONO2, CH3CCl3 and C2H2 were fitted along with PAN, whereas pre-fitted profiles were used to model the contri- bution of other contaminants like ozone. Sensitivity tests consisting in retrieval without consideration of PAN demon- strated the existence of PAN signatures in MIPAS spectra ob- tained in polluted air masses. The analysed dataset consists of 10 days between 4 October and 1 December 2003. This period covers the end of the biomass burning season in South America and South and East Africa, in which generally large amounts of pollutants are produced and distributed over wide areas of the southern hemispheric free troposphere. Indeed, elevated PAN amounts of 200-700 pptv were measured in a large plume extending from Brasil over the Southern At- lantic, Central and South Africa, the South Indian Ocean as far as Australia at altitudes between 8 and 16 km. Enhanced PAN values were also found in a much more restricted area between northern subtropical Africa and India. The most sig- nificant northern midlatitude PAN signal was detected in an area at 8 km altitude extending from China into the Chinese Sea. The average mid and high latitude PAN amounts found at 8 km were around 125 pptv in the northern, but only be- tween 50 and 75 pptv in the southern hemisphere. The PAN distribution found in the southern hemispheric tropics and subtropics is highly correlated with the jointly fitted acety- lene (C2H2), which is another pollutant produced by biomass burning, and agrees reasonably well with the CO plume de- tected during end of September 2003 at the 275 hPa level ( 10 km) by the Measurement of Pollution in the Tropo- sphere (MOPITT) instrument on the Terra satellite. Simi- lar southern hemispheric PAN amounts were also observed by previous airborne measurements performed in Septem- ber/October 1992 and 1996 above the South Atlantic and the South Pacific, respectively.

  • global distributions of ho2no2 as observed by the michelson interferometer for passive Atmospheric Sounding mipas
    Journal of Geophysical Research, 2007
    Co-Authors: Gabriele Stiller, Michael Höpfner, B Funke, N Glatthor, T Von Clarmann, C Bruhl, H Fischer, U Grabowski, Patrick Jockel, Sylvia Kellmann
    Abstract:

    [1] 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 is 5 km in the upper tropospheric and stratospheric maxima. Highest stratospheric volume mixing ratios (VMRs) reaching 310 pptv at 27 km are observed at solstice conditions in subtropical latitudes and midlatitudes at the nighttime summer hemisphere, while lowest stratospheric peak VMRs as low as 38 pptv are found during polar winter near the pole. A second maximum in the upper troposphere and lower stratosphere appears from spring to the end of summer with maximum values of 80 pptv between 7 and 14 km. Retrievals based on spectroscopic line list data instead of absorption cross sections produce HO2NO2 distributions smaller by a factor of 1.5, on average. Earlier HO2NO2 measurements from balloon instruments are in good general agreement with the presented data set if the same spectroscopic data are used. Comparisons of MIPAS HO2NO2 distributions to results of the fifth-generation European Centre Hamburg general circulation model/Modular Earth Submodel System 1 (ECHAM5/MESSy1) provide agreement within 20% if near-infrared photolysis is considered. With the newly available tabulated absorption cross sections and the improved photolysis modeling, former discrepancies between HO2NO2 observations and model calculations can be considered to be largely resolved.

N Glatthor - One of the best experts on this subject based on the ideXlab platform.

  • global cfc 11 ccl 3 f and cfc 12 ccl 2 f 2 measurements with the michelson interferometer for passive Atmospheric Sounding mipas retrieval climatologies and trends
    Atmospheric Chemistry and Physics, 2012
    Co-Authors: Sylvia Kellmann, Michael Höpfner, B Funke, N Glatthor, T Von Clarmann, M Kiefer, G P Stiller, E Eckert, J Orphal, U Grabowski
    Abstract:

    Abstract. Vertical profiles of CFC-11 (CCl 3 F) and CFC-12 (CCl 2 F 2 ) have been measured with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) with global coverage under daytime and nighttime conditions. The profile retrieval is based on constrained nonlinear least squares fitting of measured limb spectral radiance to modeled spectra. CFC-11 is measured in its ν 4 -band at 850 cm −1 , and CFC-12 is analyzed in its ν 6 -band at 922 cm −1 . To stabilize the retrievals, a Tikhonov-type smoothing constraint is applied. Main retrieval error sources are measurement noise and elevation pointing uncertainties. The estimated CFC-11 retrieval errors including noise and parameter errors but excluding spectroscopic data uncertainties are below 10 pptv in the middle stratosphere, depending on altitude, the MIPAS measurement mode and the actual Atmospheric situation. For CFC-12 the total retrieval errors are below 28 pptv at an altitude resolution varying from 3 to 5 km. Time series of altitude/latitude bins were fitted by a simple parametric approach including constant and linear terms, a quasi-biennial oscillation (QBO) proxy and sine and cosine terms of several periods. In the time series from 2002 to 2011, quasi-biennial and annual oscillations are clearly visible. A decrease of stratospheric CFC mixing ratios in response to the Montreal Protocol is observed for most altitudes and latitudes. However, the trends differ from the trends measured in the troposphere, they are even positive at some latitudes and altitudes, and can in some cases only be explained by decadal changes in Atmospheric age of air spectra or vertical mixing patterns.

  • hocl chemistry in the antarctic stratospheric vortex 2002 as observed with the michelson interferometer for passive Atmospheric Sounding mipas
    Atmospheric Chemistry and Physics, 2008
    Co-Authors: Sylvia Kellmann, Michael Höpfner, N Glatthor, T Von Clarmann, G P Stiller, R Ruhnke, Oliver Kirner, T Reddmann, W Kouker
    Abstract:

    Abstract. In the 2002 Antarctic polar vortex enhanced HOCl mixing ratios were detected by the Michelson Interferometer for Passive Atmospheric Sounding both at altitudes of around 35 km (1000 K potential temperature), where HOCl abundances are ruled by gas phase chemistry and at around 18–24 km (475–625 K), which belongs to the altitude domain where heterogeneous chlorine chemistry is relevant. At altitudes of 33 to 40 km polar vortex HOCl mixing ratios were found to be around 0.14 ppbv as long as the polar vortex was intact, centered at the pole, and thus received relatively little sunlight. This is the altitude region where in midlatitudinal and tropic atmospheres peak HOCl mixing ratios significantly above 0.2 ppbv (in terms of daily mean values) are observed. After deformation and displacement of the polar vortex in the course of a major warming, ClO-rich vortex air was more exposed to sunlight, where enhanced HOx abundances led to largely increased HOCl mixing ratios (up to 0.3 ppbv), exceeding typical midlatitudinal and tropical amounts significantly. The HOCl increase was preceded by an increase of ClO. Model runs could reproduce these measurements only when the Stimpfle et al. (1979) rate constant for the reaction ClO+HO2→HOCl+O2 was used but not with the current JPL recommendation. At an altitude of 24 km, HOCl mixing ratios of up to 0.15 ppbv were detected. This HOCl enhancement, which is already visible in 18 September data, is attributed to heterogeneous chemistry, which is in agreement with observations of polar stratospheric clouds. The measurements were compared to a model run where no polar stratospheric clouds appeared during the observation period. The fact that HOCl still was produced in the model run suggests that a significant part of HOCl was generated from ClO rather than directly via heterogeneous reaction. Excess ClO, lower ClONO2 and earlier loss of HOCl in the measurements are attributed to ongoing heterogeneous chemistry which is not reproduced by the model. On 11 October, polar vortex mean daytime mixing ratios were only 0.03 ppbv.

  • global peroxyacetyl nitrate pan retrieval in the upper troposphere from limb emission spectra of the michelson interferometer for passive Atmospheric Sounding mipas
    Atmospheric Chemistry and Physics, 2007
    Co-Authors: N Glatthor, Sylvia Kellmann, Michael Höpfner, B Funke, T Von Clarmann, H Fischer, U Grabowski, M Kiefer, A Linden, Mathias Milz
    Abstract:

    We use limb emission spectra of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard the ENVIronmental SATellite (ENVISAT) to derive the first global distribution of peroxyacetyl nitrate (PAN) in the upper troposphere. PAN is generated in tropospheric air masses polluted by fuel combustion or biomass burning and acts as a reservoir and carrier of NOx in the cold free tropo- sphere. PAN exhibits continuum-like broadband structures in the mid-infrared region and was retrieved in a contigu- ous analysis window covering the wavenumber region 775- 800 cm 1 . The interfering species CCl4, HCFC-22, H2O, ClONO2, CH3CCl3 and C2H2 were fitted along with PAN, whereas pre-fitted profiles were used to model the contri- bution of other contaminants like ozone. Sensitivity tests consisting in retrieval without consideration of PAN demon- strated the existence of PAN signatures in MIPAS spectra ob- tained in polluted air masses. The analysed dataset consists of 10 days between 4 October and 1 December 2003. This period covers the end of the biomass burning season in South America and South and East Africa, in which generally large amounts of pollutants are produced and distributed over wide areas of the southern hemispheric free troposphere. Indeed, elevated PAN amounts of 200-700 pptv were measured in a large plume extending from Brasil over the Southern At- lantic, Central and South Africa, the South Indian Ocean as far as Australia at altitudes between 8 and 16 km. Enhanced PAN values were also found in a much more restricted area between northern subtropical Africa and India. The most sig- nificant northern midlatitude PAN signal was detected in an area at 8 km altitude extending from China into the Chinese Sea. The average mid and high latitude PAN amounts found at 8 km were around 125 pptv in the northern, but only be- tween 50 and 75 pptv in the southern hemisphere. The PAN distribution found in the southern hemispheric tropics and subtropics is highly correlated with the jointly fitted acety- lene (C2H2), which is another pollutant produced by biomass burning, and agrees reasonably well with the CO plume de- tected during end of September 2003 at the 275 hPa level ( 10 km) by the Measurement of Pollution in the Tropo- sphere (MOPITT) instrument on the Terra satellite. Simi- lar southern hemispheric PAN amounts were also observed by previous airborne measurements performed in Septem- ber/October 1992 and 1996 above the South Atlantic and the South Pacific, respectively.

  • global distributions of ho2no2 as observed by the michelson interferometer for passive Atmospheric Sounding mipas
    Journal of Geophysical Research, 2007
    Co-Authors: Gabriele Stiller, Michael Höpfner, B Funke, N Glatthor, T Von Clarmann, C Bruhl, H Fischer, U Grabowski, Patrick Jockel, Sylvia Kellmann
    Abstract:

    [1] 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 is 5 km in the upper tropospheric and stratospheric maxima. Highest stratospheric volume mixing ratios (VMRs) reaching 310 pptv at 27 km are observed at solstice conditions in subtropical latitudes and midlatitudes at the nighttime summer hemisphere, while lowest stratospheric peak VMRs as low as 38 pptv are found during polar winter near the pole. A second maximum in the upper troposphere and lower stratosphere appears from spring to the end of summer with maximum values of 80 pptv between 7 and 14 km. Retrievals based on spectroscopic line list data instead of absorption cross sections produce HO2NO2 distributions smaller by a factor of 1.5, on average. Earlier HO2NO2 measurements from balloon instruments are in good general agreement with the presented data set if the same spectroscopic data are used. Comparisons of MIPAS HO2NO2 distributions to results of the fifth-generation European Centre Hamburg general circulation model/Modular Earth Submodel System 1 (ECHAM5/MESSy1) provide agreement within 20% if near-infrared photolysis is considered. With the newly available tabulated absorption cross sections and the improved photolysis modeling, former discrepancies between HO2NO2 observations and model calculations can be considered to be largely resolved.

  • global stratospheric hocl distributions retrieved from infrared limb emission spectra recorded by the michelson interferometer for passive Atmospheric Sounding mipas
    Journal of Geophysical Research, 2006
    Co-Authors: T Von Clarmann, Sylvia Kellmann, Andrea Linden, Gizaw Mengistu Tsidu, Mathias Milz, Michael Höpfner, N Glatthor, T Steck, U Grabowski, G Stiller
    Abstract:

    [1] Vertical profiles of stratospheric HOCl were retrieved from limb emission spectra recorded by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) aboard the Envisat research satellite. These are the first HOCl measurements with global coverage. The ν2 transitions between 1215.725 and 1275.550 cm−1 were used for inference of the vertical profiles. The maximal volume mixing ratios were found in the tropics at altitudes of ∼35 km (daytime) and ∼37 km (nighttime), with values up to 0.22 ppbv and 0.23 ppbv for zonal mean values at 5° latitude binning. The peak altitude of nonpolar nighttime measurements is on average higher by 2.4 ± 0.3 km compared to nonpolar daytime measurements and higher by 2.2 ± 0.3 km at high latitudes poleward of ±45° compared to respective equatorward latitudes. The diurnal variability is largest at 30°S at 46 km altitude, reaching amplitudes of 0.11 ppbv. In the Antarctic a secondary peak at 23–25 km (0.14 ppbv) was found on 19–24 September 2002, which is attributed to heterogeneous chemistry. An estimated single-profile precision of 0.03–0.08 ppbv could be achieved at an altitude resolution of 9 km in an altitude range between 20 and 50 km. Taking the trend into account, these measurements are reasonably consistent with former far-infrared measurements.

U Grabowski - One of the best experts on this subject based on the ideXlab platform.

  • global cfc 11 ccl 3 f and cfc 12 ccl 2 f 2 measurements with the michelson interferometer for passive Atmospheric Sounding mipas retrieval climatologies and trends
    Atmospheric Chemistry and Physics, 2012
    Co-Authors: Sylvia Kellmann, Michael Höpfner, B Funke, N Glatthor, T Von Clarmann, M Kiefer, G P Stiller, E Eckert, J Orphal, U Grabowski
    Abstract:

    Abstract. Vertical profiles of CFC-11 (CCl 3 F) and CFC-12 (CCl 2 F 2 ) have been measured with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) with global coverage under daytime and nighttime conditions. The profile retrieval is based on constrained nonlinear least squares fitting of measured limb spectral radiance to modeled spectra. CFC-11 is measured in its ν 4 -band at 850 cm −1 , and CFC-12 is analyzed in its ν 6 -band at 922 cm −1 . To stabilize the retrievals, a Tikhonov-type smoothing constraint is applied. Main retrieval error sources are measurement noise and elevation pointing uncertainties. The estimated CFC-11 retrieval errors including noise and parameter errors but excluding spectroscopic data uncertainties are below 10 pptv in the middle stratosphere, depending on altitude, the MIPAS measurement mode and the actual Atmospheric situation. For CFC-12 the total retrieval errors are below 28 pptv at an altitude resolution varying from 3 to 5 km. Time series of altitude/latitude bins were fitted by a simple parametric approach including constant and linear terms, a quasi-biennial oscillation (QBO) proxy and sine and cosine terms of several periods. In the time series from 2002 to 2011, quasi-biennial and annual oscillations are clearly visible. A decrease of stratospheric CFC mixing ratios in response to the Montreal Protocol is observed for most altitudes and latitudes. However, the trends differ from the trends measured in the troposphere, they are even positive at some latitudes and altitudes, and can in some cases only be explained by decadal changes in Atmospheric age of air spectra or vertical mixing patterns.

  • analysis of nonlocal thermodynamic equilibrium co 4 7 μm fundamental isotopic and hot band emissions measured by the michelson interferometer for passive Atmospheric Sounding on envisat
    Journal of Geophysical Research, 2007
    Co-Authors: B Funke, Michael Höpfner, M Lopezpuertas, T Von Clarmann, U Grabowski, D Bermejopantaleon, G P Stiller, M Kaufmann
    Abstract:

    [1] Nonlocal thermodynamic equilibrium (non-LTE) simulations of the 12C16O(1 → 0) fundamental band, the 12C16O(2 → 1) hot band, and the isotopic 13C16O(1 → 0) band performed with the Generic Radiative Transfer and non-LTE population Algorithm (GRANADA) and the Karlsruhe Optimized and Precise Radiative Transfer Algorithm (KOPRA) have been compared to spectrally resolved 4.7 μm radiances measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). The performance of the non-LTE simulation has been assessed in terms of band radiance ratios in order to avoid a compensation of possible non-LTE model errors by retrieval errors in the CO abundances inferred from MIPAS data with the same non-LTE algorithms. The agreement with the measurements is within 5% for the fundamental band and within 10% for the hot band. Simulated 13C16O radiances agree with the measurements within the instrumental noise error. Solar reflectance at the surface or clouds has been identified as an important additional excitation mechanism for the CO(2) state. The study represents a thorough validation of the non-LTE scheme used in the retrieval of CO abundances from MIPAS data.

  • global peroxyacetyl nitrate pan retrieval in the upper troposphere from limb emission spectra of the michelson interferometer for passive Atmospheric Sounding mipas
    Atmospheric Chemistry and Physics, 2007
    Co-Authors: N Glatthor, Sylvia Kellmann, Michael Höpfner, B Funke, T Von Clarmann, H Fischer, U Grabowski, M Kiefer, A Linden, Mathias Milz
    Abstract:

    We use limb emission spectra of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard the ENVIronmental SATellite (ENVISAT) to derive the first global distribution of peroxyacetyl nitrate (PAN) in the upper troposphere. PAN is generated in tropospheric air masses polluted by fuel combustion or biomass burning and acts as a reservoir and carrier of NOx in the cold free tropo- sphere. PAN exhibits continuum-like broadband structures in the mid-infrared region and was retrieved in a contigu- ous analysis window covering the wavenumber region 775- 800 cm 1 . The interfering species CCl4, HCFC-22, H2O, ClONO2, CH3CCl3 and C2H2 were fitted along with PAN, whereas pre-fitted profiles were used to model the contri- bution of other contaminants like ozone. Sensitivity tests consisting in retrieval without consideration of PAN demon- strated the existence of PAN signatures in MIPAS spectra ob- tained in polluted air masses. The analysed dataset consists of 10 days between 4 October and 1 December 2003. This period covers the end of the biomass burning season in South America and South and East Africa, in which generally large amounts of pollutants are produced and distributed over wide areas of the southern hemispheric free troposphere. Indeed, elevated PAN amounts of 200-700 pptv were measured in a large plume extending from Brasil over the Southern At- lantic, Central and South Africa, the South Indian Ocean as far as Australia at altitudes between 8 and 16 km. Enhanced PAN values were also found in a much more restricted area between northern subtropical Africa and India. The most sig- nificant northern midlatitude PAN signal was detected in an area at 8 km altitude extending from China into the Chinese Sea. The average mid and high latitude PAN amounts found at 8 km were around 125 pptv in the northern, but only be- tween 50 and 75 pptv in the southern hemisphere. The PAN distribution found in the southern hemispheric tropics and subtropics is highly correlated with the jointly fitted acety- lene (C2H2), which is another pollutant produced by biomass burning, and agrees reasonably well with the CO plume de- tected during end of September 2003 at the 275 hPa level ( 10 km) by the Measurement of Pollution in the Tropo- sphere (MOPITT) instrument on the Terra satellite. Simi- lar southern hemispheric PAN amounts were also observed by previous airborne measurements performed in Septem- ber/October 1992 and 1996 above the South Atlantic and the South Pacific, respectively.

  • global distributions of ho2no2 as observed by the michelson interferometer for passive Atmospheric Sounding mipas
    Journal of Geophysical Research, 2007
    Co-Authors: Gabriele Stiller, Michael Höpfner, B Funke, N Glatthor, T Von Clarmann, C Bruhl, H Fischer, U Grabowski, Patrick Jockel, Sylvia Kellmann
    Abstract:

    [1] 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 is 5 km in the upper tropospheric and stratospheric maxima. Highest stratospheric volume mixing ratios (VMRs) reaching 310 pptv at 27 km are observed at solstice conditions in subtropical latitudes and midlatitudes at the nighttime summer hemisphere, while lowest stratospheric peak VMRs as low as 38 pptv are found during polar winter near the pole. A second maximum in the upper troposphere and lower stratosphere appears from spring to the end of summer with maximum values of 80 pptv between 7 and 14 km. Retrievals based on spectroscopic line list data instead of absorption cross sections produce HO2NO2 distributions smaller by a factor of 1.5, on average. Earlier HO2NO2 measurements from balloon instruments are in good general agreement with the presented data set if the same spectroscopic data are used. Comparisons of MIPAS HO2NO2 distributions to results of the fifth-generation European Centre Hamburg general circulation model/Modular Earth Submodel System 1 (ECHAM5/MESSy1) provide agreement within 20% if near-infrared photolysis is considered. With the newly available tabulated absorption cross sections and the improved photolysis modeling, former discrepancies between HO2NO2 observations and model calculations can be considered to be largely resolved.

  • global stratospheric hocl distributions retrieved from infrared limb emission spectra recorded by the michelson interferometer for passive Atmospheric Sounding mipas
    Journal of Geophysical Research, 2006
    Co-Authors: T Von Clarmann, Sylvia Kellmann, Andrea Linden, Gizaw Mengistu Tsidu, Mathias Milz, Michael Höpfner, N Glatthor, T Steck, U Grabowski, G Stiller
    Abstract:

    [1] Vertical profiles of stratospheric HOCl were retrieved from limb emission spectra recorded by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) aboard the Envisat research satellite. These are the first HOCl measurements with global coverage. The ν2 transitions between 1215.725 and 1275.550 cm−1 were used for inference of the vertical profiles. The maximal volume mixing ratios were found in the tropics at altitudes of ∼35 km (daytime) and ∼37 km (nighttime), with values up to 0.22 ppbv and 0.23 ppbv for zonal mean values at 5° latitude binning. The peak altitude of nonpolar nighttime measurements is on average higher by 2.4 ± 0.3 km compared to nonpolar daytime measurements and higher by 2.2 ± 0.3 km at high latitudes poleward of ±45° compared to respective equatorward latitudes. The diurnal variability is largest at 30°S at 46 km altitude, reaching amplitudes of 0.11 ppbv. In the Antarctic a secondary peak at 23–25 km (0.14 ppbv) was found on 19–24 September 2002, which is attributed to heterogeneous chemistry. An estimated single-profile precision of 0.03–0.08 ppbv could be achieved at an altitude resolution of 9 km in an altitude range between 20 and 50 km. Taking the trend into account, these measurements are reasonably consistent with former far-infrared measurements.

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  • global cfc 11 ccl 3 f and cfc 12 ccl 2 f 2 measurements with the michelson interferometer for passive Atmospheric Sounding mipas retrieval climatologies and trends
    Atmospheric Chemistry and Physics, 2012
    Co-Authors: Sylvia Kellmann, Michael Höpfner, B Funke, N Glatthor, T Von Clarmann, M Kiefer, G P Stiller, E Eckert, J Orphal, U Grabowski
    Abstract:

    Abstract. Vertical profiles of CFC-11 (CCl 3 F) and CFC-12 (CCl 2 F 2 ) have been measured with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) with global coverage under daytime and nighttime conditions. The profile retrieval is based on constrained nonlinear least squares fitting of measured limb spectral radiance to modeled spectra. CFC-11 is measured in its ν 4 -band at 850 cm −1 , and CFC-12 is analyzed in its ν 6 -band at 922 cm −1 . To stabilize the retrievals, a Tikhonov-type smoothing constraint is applied. Main retrieval error sources are measurement noise and elevation pointing uncertainties. The estimated CFC-11 retrieval errors including noise and parameter errors but excluding spectroscopic data uncertainties are below 10 pptv in the middle stratosphere, depending on altitude, the MIPAS measurement mode and the actual Atmospheric situation. For CFC-12 the total retrieval errors are below 28 pptv at an altitude resolution varying from 3 to 5 km. Time series of altitude/latitude bins were fitted by a simple parametric approach including constant and linear terms, a quasi-biennial oscillation (QBO) proxy and sine and cosine terms of several periods. In the time series from 2002 to 2011, quasi-biennial and annual oscillations are clearly visible. A decrease of stratospheric CFC mixing ratios in response to the Montreal Protocol is observed for most altitudes and latitudes. However, the trends differ from the trends measured in the troposphere, they are even positive at some latitudes and altitudes, and can in some cases only be explained by decadal changes in Atmospheric age of air spectra or vertical mixing patterns.

  • hocl chemistry in the antarctic stratospheric vortex 2002 as observed with the michelson interferometer for passive Atmospheric Sounding mipas
    Atmospheric Chemistry and Physics, 2008
    Co-Authors: Sylvia Kellmann, Michael Höpfner, N Glatthor, T Von Clarmann, G P Stiller, R Ruhnke, Oliver Kirner, T Reddmann, W Kouker
    Abstract:

    Abstract. In the 2002 Antarctic polar vortex enhanced HOCl mixing ratios were detected by the Michelson Interferometer for Passive Atmospheric Sounding both at altitudes of around 35 km (1000 K potential temperature), where HOCl abundances are ruled by gas phase chemistry and at around 18–24 km (475–625 K), which belongs to the altitude domain where heterogeneous chlorine chemistry is relevant. At altitudes of 33 to 40 km polar vortex HOCl mixing ratios were found to be around 0.14 ppbv as long as the polar vortex was intact, centered at the pole, and thus received relatively little sunlight. This is the altitude region where in midlatitudinal and tropic atmospheres peak HOCl mixing ratios significantly above 0.2 ppbv (in terms of daily mean values) are observed. After deformation and displacement of the polar vortex in the course of a major warming, ClO-rich vortex air was more exposed to sunlight, where enhanced HOx abundances led to largely increased HOCl mixing ratios (up to 0.3 ppbv), exceeding typical midlatitudinal and tropical amounts significantly. The HOCl increase was preceded by an increase of ClO. Model runs could reproduce these measurements only when the Stimpfle et al. (1979) rate constant for the reaction ClO+HO2→HOCl+O2 was used but not with the current JPL recommendation. At an altitude of 24 km, HOCl mixing ratios of up to 0.15 ppbv were detected. This HOCl enhancement, which is already visible in 18 September data, is attributed to heterogeneous chemistry, which is in agreement with observations of polar stratospheric clouds. The measurements were compared to a model run where no polar stratospheric clouds appeared during the observation period. The fact that HOCl still was produced in the model run suggests that a significant part of HOCl was generated from ClO rather than directly via heterogeneous reaction. Excess ClO, lower ClONO2 and earlier loss of HOCl in the measurements are attributed to ongoing heterogeneous chemistry which is not reproduced by the model. On 11 October, polar vortex mean daytime mixing ratios were only 0.03 ppbv.

  • global peroxyacetyl nitrate pan retrieval in the upper troposphere from limb emission spectra of the michelson interferometer for passive Atmospheric Sounding mipas
    Atmospheric Chemistry and Physics, 2007
    Co-Authors: N Glatthor, Sylvia Kellmann, Michael Höpfner, B Funke, T Von Clarmann, H Fischer, U Grabowski, M Kiefer, A Linden, Mathias Milz
    Abstract:

    We use limb emission spectra of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard the ENVIronmental SATellite (ENVISAT) to derive the first global distribution of peroxyacetyl nitrate (PAN) in the upper troposphere. PAN is generated in tropospheric air masses polluted by fuel combustion or biomass burning and acts as a reservoir and carrier of NOx in the cold free tropo- sphere. PAN exhibits continuum-like broadband structures in the mid-infrared region and was retrieved in a contigu- ous analysis window covering the wavenumber region 775- 800 cm 1 . The interfering species CCl4, HCFC-22, H2O, ClONO2, CH3CCl3 and C2H2 were fitted along with PAN, whereas pre-fitted profiles were used to model the contri- bution of other contaminants like ozone. Sensitivity tests consisting in retrieval without consideration of PAN demon- strated the existence of PAN signatures in MIPAS spectra ob- tained in polluted air masses. The analysed dataset consists of 10 days between 4 October and 1 December 2003. This period covers the end of the biomass burning season in South America and South and East Africa, in which generally large amounts of pollutants are produced and distributed over wide areas of the southern hemispheric free troposphere. Indeed, elevated PAN amounts of 200-700 pptv were measured in a large plume extending from Brasil over the Southern At- lantic, Central and South Africa, the South Indian Ocean as far as Australia at altitudes between 8 and 16 km. Enhanced PAN values were also found in a much more restricted area between northern subtropical Africa and India. The most sig- nificant northern midlatitude PAN signal was detected in an area at 8 km altitude extending from China into the Chinese Sea. The average mid and high latitude PAN amounts found at 8 km were around 125 pptv in the northern, but only be- tween 50 and 75 pptv in the southern hemisphere. The PAN distribution found in the southern hemispheric tropics and subtropics is highly correlated with the jointly fitted acety- lene (C2H2), which is another pollutant produced by biomass burning, and agrees reasonably well with the CO plume de- tected during end of September 2003 at the 275 hPa level ( 10 km) by the Measurement of Pollution in the Tropo- sphere (MOPITT) instrument on the Terra satellite. Simi- lar southern hemispheric PAN amounts were also observed by previous airborne measurements performed in Septem- ber/October 1992 and 1996 above the South Atlantic and the South Pacific, respectively.

  • global distributions of ho2no2 as observed by the michelson interferometer for passive Atmospheric Sounding mipas
    Journal of Geophysical Research, 2007
    Co-Authors: Gabriele Stiller, Michael Höpfner, B Funke, N Glatthor, T Von Clarmann, C Bruhl, H Fischer, U Grabowski, Patrick Jockel, Sylvia Kellmann
    Abstract:

    [1] 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 is 5 km in the upper tropospheric and stratospheric maxima. Highest stratospheric volume mixing ratios (VMRs) reaching 310 pptv at 27 km are observed at solstice conditions in subtropical latitudes and midlatitudes at the nighttime summer hemisphere, while lowest stratospheric peak VMRs as low as 38 pptv are found during polar winter near the pole. A second maximum in the upper troposphere and lower stratosphere appears from spring to the end of summer with maximum values of 80 pptv between 7 and 14 km. Retrievals based on spectroscopic line list data instead of absorption cross sections produce HO2NO2 distributions smaller by a factor of 1.5, on average. Earlier HO2NO2 measurements from balloon instruments are in good general agreement with the presented data set if the same spectroscopic data are used. Comparisons of MIPAS HO2NO2 distributions to results of the fifth-generation European Centre Hamburg general circulation model/Modular Earth Submodel System 1 (ECHAM5/MESSy1) provide agreement within 20% if near-infrared photolysis is considered. With the newly available tabulated absorption cross sections and the improved photolysis modeling, former discrepancies between HO2NO2 observations and model calculations can be considered to be largely resolved.

  • global stratospheric hocl distributions retrieved from infrared limb emission spectra recorded by the michelson interferometer for passive Atmospheric Sounding mipas
    Journal of Geophysical Research, 2006
    Co-Authors: T Von Clarmann, Sylvia Kellmann, Andrea Linden, Gizaw Mengistu Tsidu, Mathias Milz, Michael Höpfner, N Glatthor, T Steck, U Grabowski, G Stiller
    Abstract:

    [1] Vertical profiles of stratospheric HOCl were retrieved from limb emission spectra recorded by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) aboard the Envisat research satellite. These are the first HOCl measurements with global coverage. The ν2 transitions between 1215.725 and 1275.550 cm−1 were used for inference of the vertical profiles. The maximal volume mixing ratios were found in the tropics at altitudes of ∼35 km (daytime) and ∼37 km (nighttime), with values up to 0.22 ppbv and 0.23 ppbv for zonal mean values at 5° latitude binning. The peak altitude of nonpolar nighttime measurements is on average higher by 2.4 ± 0.3 km compared to nonpolar daytime measurements and higher by 2.2 ± 0.3 km at high latitudes poleward of ±45° compared to respective equatorward latitudes. The diurnal variability is largest at 30°S at 46 km altitude, reaching amplitudes of 0.11 ppbv. In the Antarctic a secondary peak at 23–25 km (0.14 ppbv) was found on 19–24 September 2002, which is attributed to heterogeneous chemistry. An estimated single-profile precision of 0.03–0.08 ppbv could be achieved at an altitude resolution of 9 km in an altitude range between 20 and 50 km. Taking the trend into account, these measurements are reasonably consistent with former far-infrared measurements.