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1
Perrin, Agnès, Jean-Marie Flaud, Marco Ridolfi, Jean Vander Auwera, and Massimo Carlotti. "MIPAS database: new HNO<sub>3</sub> line parameters at 7.6 µm validated with MIPAS satellite measurements." Atmospheric Measurement Techniques 9, no. 5 (May 10, 2016): 2067–76. http://dx.doi.org/10.5194/amt-9-2067-2016.
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Abstract. Improved line positions and intensities have been generated for the 7.6 µm spectral region of nitric acid. They were obtained relying on a recent reinvestigation of the nitric acid band system at 7.6 µm and comparisons of HNO3 volume mixing ratio profiles retrieved from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) limb emission radiances in the 11 and 7.6 µm domains. This has led to an improved database called MIPAS-2015. Comparisons with available laboratory information (individual line intensities, integrated absorption cross sections, and absorption cross sections) show that MIPAS-2015 provides an improved description of the 7.6 µm region of nitric acid. This study should help to improve HNO3 satellite retrievals by allowing measurements to be performed simultaneously in the 11 and 7.6 µm micro-windows. In particular, it should be useful to analyze existing MIPAS and IASI spectra as well as spectra to be recorded by the forthcoming Infrared Atmospheric Sounding Interferometer – New Generation (IASI-NG) instrument.
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Perrin, A., J. M. Flaud, M. Ridolfi, J. Vander Auwera, and M. Carlotti. "MIPAS database: new HNO<sub>3</sub> line parameters at 7.6 μm validated with MIPAS satellite measurements." Atmospheric Measurement Techniques Discussions 8, no. 11 (November 10, 2015): 11643–71. http://dx.doi.org/10.5194/amtd-8-11643-2015.
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Abstract. Improved line positions and intensities have been generated for the 7.6 μm spectral region of nitric acid. They were obtained relying on a recent reinvestigation of the nitric acid band system at 7.6 μm and comparisons of HNO3 volume mixing ratio profiles retrieved from the "Michelson Interferometer for Passive Atmospheric Sounding" (MIPAS) limb emission radiances in the 11 and 7.6 μm domains. This has led to an improved database called "MIPAS-2015". Comparisons with available laboratory information (individual line intensities, integrated absorption cross sections, and absorption cross sections) show that MIPAS-2015 provides an improved description of the 7.6 μm region of nitric acid. This study should help to improve HNO3 satellite retrievals by allowing measurements to be performed simultaneously in the 11 and 7.6 μm micro-windows. In particular, it should be useful to analyze existing MIPAS and IASI spectra as well as spectra to be recorded by the forthcoming "Infrared Atmospheric Sounding Interferometer – New Generation" (IASI-NG) instrument.
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Flaud, J. M., G. Brizzi, M. Carlotti, A. Perrin, and M. Ridolfi. "MIPAS database: Validation of HNO<sub>3</sub> line parameters using MIPAS satellite measurements." Atmospheric Chemistry and Physics 6, no. 12 (November 3, 2006): 5037–48. http://dx.doi.org/10.5194/acp-6-5037-2006.
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Abstract. Using new and accurate experimental results concerning the spectroscopic properties of the HNO3 molecule as well as improved theoretical methods it has been possible to generate an improved set of line parameters for this molecule in the spectral range covered by the MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) experiment. These line parameters, which have been validated using broadband atmospheric spectra recorded by MIPAS, have been included in the last version of the MIPAS spectroscopic database to be used for future processing of the MIPAS spectra.
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Flaud, J. M., G. Brizzi, M. Carlotti, A. Perrin, and M. Ridolfi. "MIPAS database: Validation of HNO<sub>3</sub> line parameters using MIPAS satellite measurements." Atmospheric Chemistry and Physics Discussions 6, no. 3 (May 29, 2006): 4251–72. http://dx.doi.org/10.5194/acpd-6-4251-2006.
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Abstract. Using new and accurate experimental results concerning the spectroscopic properties of the HNO3 molecule as well as improved theoretical methods it has been possible to generate an improved set of line parameters for this molecule in the spectral range covered by the MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) experiment. These line parameters, which have been validated using broadband atmospheric spectra recorded by MIPAS, have been included in the last version of the MIPAS spectroscopic database to be used for future processing of the MIPAS spectra.
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Milz, M., T. v. Clarmann, P. Bernath, C. Boone, S. A. Buehler, S. Chauhan, B. Deuber, et al. "Validation of water vapour profiles (version 13) retrieved by the IMK/IAA scientific retrieval processor based on full resolution spectra measured by MIPAS on board Envisat." Atmospheric Measurement Techniques Discussions 2, no. 1 (February 25, 2009): 489–559. http://dx.doi.org/10.5194/amtd-2-489-2009.
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Abstract. Vertical profiles of stratospheric water vapour measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) between September 2002 and March 2004 and retrieved with the IMK/IAA scientific retrieval processor were compared to a number of independent measurements in order to estimate the bias and to validate the existing precision estimates of the MIPAS data. The independent instruments were: the Halogen Occultation Experiment (HALOE), the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS), the Improved Limb Atmospheric Spectrometer-II (ILAS-II), the Polar Ozone and Aerosol Measurement (POAM III) instrument, the Middle Atmospheric Water Vapour Radiometer (MIAWARA), the Michelson Interferometer for Passive Atmospheric Sounding, balloon-borne version (MIPAS-B), the Airborne Microwave Stratospheric Observing System (AMSOS), the Fluorescent Stratospheric Hygrometer for Balloon (FLASH-B), the NOAA frostpoint hygrometer, and the Fast In Situ Hygrometer (FISH). In the stratosphere there is no clear indication of a bias in MIPAS data, because the independent measurements in some cases are drier and in some cases are moister than the MIPAS measurements. Compared to the infrared measurements of MIPAS, measurements in the ultraviolet and visible have a tendency to be high, whereas microwave measurements have a tendency to be low. The results of χ2-based precision validation are somewhat controversial among the comparison estimates. However, for comparison instruments whose error budget also includes errors due to uncertainties in spectrally interfering species and where good coincidences were found, the χ2 values found are in the expected range or even below. This suggests that there is no evidence of systematically underestimated MIPAS random errors.
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Milz, M., T. v. Clarmann, P. Bernath, C. Boone, S. A. Buehler, S. Chauhan, B. Deuber, et al. "Validation of water vapour profiles (version 13) retrieved by the IMK/IAA scientific retrieval processor based on full resolution spectra measured by MIPAS on board Envisat." Atmospheric Measurement Techniques 2, no. 2 (July 27, 2009): 379–99. http://dx.doi.org/10.5194/amt-2-379-2009.
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Abstract. Vertical profiles of stratospheric water vapour measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) with the full resolution mode between September 2002 and March 2004 and retrieved with the IMK/IAA scientific retrieval processor were compared to a number of independent measurements in order to estimate the bias and to validate the existing precision estimates of the MIPAS data. The estimated precision for MIPAS is 5 to 10% in the stratosphere, depending on altitude, latitude, and season. The independent instruments were: the Halogen Occultation Experiment (HALOE), the Atmospheric Chemistry Experiment Fourier Transform Spectrometer (ACE-FTS), the Improved Limb Atmospheric Spectrometer-II (ILAS-II), the Polar Ozone and Aerosol Measurement (POAM III) instrument, the Middle Atmospheric Water Vapour Radiometer (MIAWARA), the Michelson Interferometer for Passive Atmospheric Sounding, balloon-borne version (MIPAS-B), the Airborne Microwave Stratospheric Observing System (AMSOS), the Fluorescent Stratospheric Hygrometer for Balloon (FLASH-B), the NOAA frostpoint hygrometer, and the Fast In Situ Hygrometer (FISH). For the in-situ measurements and the ground based, air- and balloon borne remote sensing instruments, the measurements are restricted to central and northern Europe. The comparisons to satellite-borne instruments are predominantly at mid- to high latitudes on both hemispheres. In the stratosphere there is no clear indication of a bias in MIPAS data, because the independent measurements in some cases are drier and in some cases are moister than the MIPAS measurements. Compared to the infrared measurements of MIPAS, measurements in the ultraviolet and visible have a tendency to be high, whereas microwave measurements have a tendency to be low. The results of χ2-based precision validation are somewhat controversial among the comparison estimates. However, for comparison instruments whose error budget also includes errors due to uncertainties in spectrally interfering species and where good coincidences were found, the χ2 values found are in the expected range or even below. This suggests that there is no evidence of systematically underestimated MIPAS random errors.
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Hurley, J., A. Dudhia, and R. G. Grainger. "Retrieval of macrophysical cloud parameters from MIPAS: algorithm description and preliminary validation." Atmospheric Measurement Techniques Discussions 3, no. 4 (August 26, 2010): 3877–906. http://dx.doi.org/10.5194/amtd-3-3877-2010.
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Abstract. The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard ENVISAT has the potential to be particularly useful for studying high, thin clouds, which have been difficult to observe in the past. This paper details the development, implementation and testing of an optimal-estimation-type retrieval for three macrophysical cloud parameters (cloud top height, cloud top temperature and cloud extinction coefficient) from infrared spectra measured by MIPAS, employing additional information derived to improve the choice of a priori. The retrieval is applied and initially validated on MIPAS data. From application to MIPAS data, the retrieved cloud top heights are assessed to be accurate to within 50 m, the cloud top temperatures to within 0.5 K and extinction coefficients to within a factor of 15%. This algorithm has been adopted by the European Space Agency's ''MIPclouds'' project, which itself recognises the potential of MIPAS beyond monitoring atmospheric chemistry and seeks to study clouds themselves rigorously using MIPAS.
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Kleinert, Anne, Manfred Birk, Gaétan Perron, and Georg Wagner. "Level 1b error budget for MIPAS on ENVISAT." Atmospheric Measurement Techniques 11, no. 10 (October 17, 2018): 5657–72. http://dx.doi.org/10.5194/amt-11-5657-2018.
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Abstract. The Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) is a Fourier transform spectrometer measuring the radiance emitted from the atmosphere in limb geometry in the thermal infrared spectral region. It was operated onboard the ENVISAT satellite from 2002 to 2012. Calibrated and geolocated spectra, the so-called level 1b data, are the basis for the retrieval of atmospheric parameters. In this paper we present the error budget for the level 1b data of the most recent data version 8 in terms of radiometric, spectral, and line of sight accuracy. The major changes of version 8 compared to older versions are also described. The impact of the different error sources on the spectra is characterized in terms of spectral, vertical, and temporal correlation because these correlations have an impact on the quality of the retrieved quantities. The radiometric error is in the order of 1 % to 2.4 %, the spectral accuracy is better than 0.3 ppm, and the line of sight accuracy at the tangent point is around 400 m. All errors are well within the requirements, and the achieved accuracy allows atmospheric parameters to be retrieved from the measurements with high quality.
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Piccolo, C., and A. Dudhia. "Precision validation of MIPAS-Envisat products." Atmospheric Chemistry and Physics 7, no. 8 (April 17, 2007): 1915–23. http://dx.doi.org/10.5194/acp-7-1915-2007.
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Abstract. This paper discusses the variation and validation of the precision, or estimated random error, associated with the ESA Level 2 products from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). This quantity represents the propagation of the radiometric noise from the spectra through the retrieval process into the Level 2 profile values. The noise itself varies with time, steadily rising between ice decontamination events, but the Level 2 precision has a greater variation due to the atmospheric temperature which controls the total radiance received. Hence, for all species, the precision varies latitudinally/seasonally with temperature, with a small superimposed temporal structure determined by the degree of ice contamination on the detectors. The precision validation involves comparing two MIPAS retrievals at the intersections of ascending/descending orbits. For 5 days per month of full resolution MIPAS operation, the standard deviation of the matching profile pairs is computed and compared with the precision given in the MIPAS Level 2 data, except for NO2 since it has a large diurnal variation between ascending/descending intersections. Even taking into account the propagation of the pressure-temperature retrieval errors into the VMR retrieval, the standard deviation of the matching pairs is usually a factor 1–2 larger than the precision. This is thought to be due to effects such as horizontal inhomogeneity of the atmosphere and instability of the retrieval.
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Piccolo, C., and A. Dudhia. "Precision validation of MIPAS-Envisat products." Atmospheric Chemistry and Physics Discussions 7, no. 1 (January 18, 2007): 911–29. http://dx.doi.org/10.5194/acpd-7-911-2007.
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Abstract. This paper discusses the variation and validation of the precision, or estimated random error, associated with the ESA Level 2 products from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). This quantity represents the propagation of the radiometric noise from the spectra through the retrieval process into the Level 2 profile values. The noise itself varies with time, steadily rising between decontamination events, but the Level 2 precision has a greater variation due to the atmospheric temperature which controls the total radiance received. Hence, for all species, the precision varies latitudinally/seasonally with temperature, with a small superimposed temporal structure determined by the degree of ice contamination on the detectors. The precision validation involves comparing two MIPAS retrievals at the intersections of ascending/descending orbits. For 5 days per month of full resolution MIPAS operation, the standard deviation of the matching profile pairs is computed and compared with the precision given in the MIPAS Level 2 data. Even taking into account the propagation of the pressure-temperature retrieval errors into the VMR retrieval, the standard deviation of the matching pairs is usually a factor 1–2 larger than the precision. This is thought to be due to effects such as horizontal inhomogeneity of the atmosphere and instability of the retrieval.
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Höpfner, M., J. Orphal, T. von Clarmann, G. Stiller, and H. Fischer. "Stratospheric BrONO<sub>2</sub> observed by MIPAS." Atmospheric Chemistry and Physics 9, no. 5 (March 6, 2009): 1735–46. http://dx.doi.org/10.5194/acp-9-1735-2009.
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Abstract. The first measurements of stratospheric bromine nitrate (BrONO2) are reported. Bromine nitrate has been clearly identified in atmospheric infrared emission spectra recorded with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) aboard the European Envisat satellite, and stratospheric concentration profiles have been determined for different conditions (day and night, different latitudes). The BrONO2 concentrations show strong day/night variations, with much lower concentrations during the day. Maximum volume mixing ratios observed during night are 20 to 25 pptv. The observed concentration profiles are in agreement with estimations from photochemical models and show that the current understanding of stratospheric bromine chemistry is generally correct.
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Hurley, J., A. Dudhia, and R. G. Grainger. "Cloud detection for MIPAS using singular vector decomposition." Atmospheric Measurement Techniques 2, no. 2 (September 18, 2009): 533–47. http://dx.doi.org/10.5194/amt-2-533-2009.
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Abstract. Satellite-borne high-spectral-resolution limb sounders, such as the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard ENVISAT, provide information on clouds, especially optically thin clouds, which have been difficult to observe in the past. The aim of this work is to develop, implement and test a reliable cloud detection method for infrared spectra measured by MIPAS. Current MIPAS cloud detection methods used operationally have been developed to detect cloud effective filling more than 30% of the measurement field-of-view (FOV), under geometric and optical considerations – and hence are limited to detecting fairly thick cloud, or large physical extents of thin cloud. In order to resolve thin clouds, a new detection method using Singular Vector Decomposition (SVD) is formulated and tested. This new SVD detection method has been applied to a year's worth of MIPAS data, and qualitatively appears to be more sensitive to thin cloud than the current operational method.
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Woiwode, W., H. Oelhaf, T. Gulde, C. Piesch, G. Maucher, A. Ebersoldt, C. Keim, et al. "MIPAS-STR measurements in the arctic UTLS in winter/spring 2010: instrument characterization, retrieval and validation." Atmospheric Measurement Techniques Discussions 4, no. 6 (November 24, 2011): 7035–108. http://dx.doi.org/10.5194/amtd-4-7035-2011.
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Abstract. The mid-infrared FTIR-limb-sounder Michelson Interferometer for Passive Atmospheric Sounding – STRatospheric aircraft (MIPAS-STR) was deployed onboard the stratospheric aircraft M55 Geophysica during the RECONCILE campaign in the arctic winter/spring 2010. From the MIPAS-STR measurements, vertical profiles and 2-dimensional vertical cross-sections of temperature and trace gases are retrieved. Detailed mesoscale structures of polar vortex air, extra vortex air and vortex filaments are identified in the results at a typical vertical resolution of 1 to 2 km and typical horizontal sampling density of 45 or 25 km, depending on the sampling programme. Results are shown for the RECONCILE flight 11 on 2 March 2010 and are validated with collocated in-situ measurements of temperature, O3, CFC-11, CFC-12 and H2O. Exceptional agreement is found for the in-situ comparisons of temperature and O3, with mean differences (vertical profile/along flight track) of 0.2/−0.2 K for temperature and −0.01/0.05 ppmv for O3 and corresponding sample standard deviations of the mean differences of 0.7/0.6 K and 0.1/0.3 ppmv. The comparison of the retrieved vertical cross-sections of HNO3 from MIPAS-STR and the infrared limb-sounder Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere – New Frontiers (CRISTA-NF) indicates comprehensive agreement. We discuss MIPAS-STR in its current configuration, the spectral and radiometric calibration of the measurements and the retrieval of atmospheric parameters from the spectra. The MIPAS-STR measurements are significantly affected by continuum-like contributions, which are attributed to background aerosol and broad spectral signatures from interfering trace gases and are important for mid-infrared limb-sounding measurements in the Upper Troposphere/Lower Stratosphere (UTLS) region. Considering for continuum-like effects, we present a scheme suitable for accurate retrievals of temperature and an extended set of trace gases, including the correction of a systematic line-of-sight offset.
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Höpfner, M., J. Orphal, T. von Clarmann, G. Stiller, and H. Fischer. "Stratospheric BrONO<sub>2</sub> observed by MIPAS." Atmospheric Chemistry and Physics Discussions 8, no. 6 (November 19, 2008): 19679–705. http://dx.doi.org/10.5194/acpd-8-19679-2008.
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Abstract. The first measurements of stratospheric bromine nitrate (BrONO2) are reported. Bromine nitrate has been clearly identified in atmospheric infrared emission spectra recorded with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) aboard the European Envisat satellite, and stratospheric concentration profiles have been determined for different conditions (day and night, different latitudes). The BrONO2 concentrations show strong day/night variations, with much lower concentrations during the day. Maximum volume mixing ratios observed during night are 20 to 25 pptv. The observed concentration profiles are in agreement with estimations from photochemical models and show that the current understanding of stratospheric bromine chemistry is generally correct.
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Davies, S., G. W. Mann, K. S. Carslaw, M. P. Chipperfield, J. J. Remedios, G. Allen, A. M. Waterfall, R. Spang, and G. C. Toon. "Testing our understanding of Arctic denitrification using MIPAS-E satellite measurements in winter 2002/2003." Atmospheric Chemistry and Physics 6, no. 10 (July 31, 2006): 3149–61. http://dx.doi.org/10.5194/acp-6-3149-2006.
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Abstract. Observations of gas-phase HNO3 and N2O in the polar stratosphere from the Michelson Interferometer for Passive Atmospheric Sounding aboard the ENVISAT satellite (MIPAS-E) were made during the cold Arctic winter of 2002/2003. Vortex temperatures were unusually low in early winter and remained favourable for polar stratospheric cloud formation and denitrification until mid-January. MIPAS-E observations provide the first dataset with sufficient coverage of the polar vortex in mid-winter which enables a reasonable estimate of the timing of onset and spatial distribution of denitrification of the Arctic lower stratosphere to be performed. We use the observations from MIPAS-E to test the evolution of denitrification in the DLAPSE (Denitrification by Lagrangian Particle Sedimentation) microphysical denitrification model coupled to the SLIMCAT chemical transport model. In addition, the predicted denitrification from a simple equilibrium nitric acid trihydrate-based scheme is also compared with MIPAS-E. Modelled denitrification is compared with in-vortex NOy and N2O observations from the balloon-borne MarkIV interferometer in mid-December. Denitrification was clearly observed by MIPAS-E in mid-December 2002 and reached 80% in the core of the vortex by early January 2003. The DLAPSE model is broadly able to capture both the timing of onset and the spatial distribution of the observed denitrification. A simple thermodynamic equilibrium scheme is able to reproduce the observed denitrification in the core of the vortex but overestimates denitrification closer to the vortex edge. This study also suggests that the onset of denitrification in simple thermodynamic schemes may be earlier than in the MIPAS-E observations.
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Millán, Luis F., Nathaniel J. Livesey, Michelle L. Santee, and Thomas von Clarmann. "Characterizing sampling and quality screening biases in infrared and microwave limb sounding." Atmospheric Chemistry and Physics 18, no. 6 (March 27, 2018): 4187–99. http://dx.doi.org/10.5194/acp-18-4187-2018.
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Abstract. This study investigates orbital sampling biases and evaluates the additional impact caused by data quality screening for the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) and the Aura Microwave Limb Sounder (MLS). MIPAS acts as a proxy for typical infrared limb emission sounders, while MLS acts as a proxy for microwave limb sounders. These biases were calculated for temperature and several trace gases by interpolating model fields to real sampling patterns and, additionally, screening those locations as directed by their corresponding quality criteria. Both instruments have dense uniform sampling patterns typical of limb emission sounders, producing almost identical sampling biases. However, there is a substantial difference between the number of locations discarded. MIPAS, as a mid-infrared instrument, is very sensitive to clouds, and measurements affected by them are thus rejected from the analysis. For example, in the tropics, the MIPAS yield is strongly affected by clouds, while MLS is mostly unaffected. The results show that upper-tropospheric sampling biases in zonally averaged data, for both instruments, can be up to 10 to 30 %, depending on the species, and up to 3 K for temperature. For MIPAS, the sampling reduction due to quality screening worsens the biases, leading to values as large as 30 to 100 % for the trace gases and expanding the 3 K bias region for temperature. This type of sampling bias is largely induced by the geophysical origins of the screening (e.g. clouds). Further, analysis of long-term time series reveals that these additional quality screening biases may affect the ability to accurately detect upper-tropospheric long-term changes using such data. In contrast, MLS data quality screening removes sufficiently few points that no additional bias is introduced, although its penetration is limited to the upper troposphere, while MIPAS may cover well into the mid-troposphere in cloud-free scenarios. We emphasize that the results of this study refer only to the representativeness of the respective data, not to their intrinsic quality.
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von Clarmann, T., N. Glatthor, and J. Plieninger. "Maximum likelihood representation of MIPAS profiles." Atmospheric Measurement Techniques 8, no. 7 (July 9, 2015): 2749–57. http://dx.doi.org/10.5194/amt-8-2749-2015.
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Abstract. In order to avoid problems connected with the content of a priori information in volume mixing ratio vertical profiles measured with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), a user-friendly representation of the data has been developed which will be made available in addition to the regular data product. In this representation, the data will be provided on a fixed pressure grid coarse enough to allow a virtually unconstrained retrieval. To avoid data interpolation, the grid is chosen to be a subset of the pressure grids used by the Chemistry–Climate Model Initiative and the Data Initiative within the Stratosphere-troposphere Processes And their Role in Climate (SPARC) project as well as the Intergovernmental Panel of Climate Change climatologies and model calculations. For representation, the profiles have been transformed to boxcar base functions, which means that volume mixing ratios are constant within a layer. This representation is thought to be more adequate for comparison with model data. While this method is applicable also to vertical profiles of other species, the method is discussed using ozone as an example.
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von Clarmann, T., N. Glatthor, and J. Plieninger. "Maximum likelihood representation of MIPAS profiles." Atmospheric Measurement Techniques Discussions 8, no. 3 (March 6, 2015): 2501–20. http://dx.doi.org/10.5194/amtd-8-2501-2015.
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Abstract. In order to avoid problems connected with the content of a priori information in volume mixing ratio vertical profiles measured with the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), a user-friendly representation of the data has been developed which will be made available in addition to the regular data product. In this representation, the data will be provided on a fixed pressure grid coarse enough to allow a virtually unconstrained retrieval. As to avoid data interpolation, the grid is chosen to be a subset of the pressure grids used by the Chemistry Climate Model Initiative and the Data Initiative within the Stratosphere-troposphere Processes And their Role in Climate (SPARC) project as well as the Intergovernmental Panel of Climate Change climatologies and model calculations. For representation, the profiles have been transformed to boxcar base functions, which means that volume mixing ratios are constant within a layer. This representation is thought to be more adequate for comparison with model data. While this method is applicable also to vertical profiles of other species, the method is discussed using ozone as an example.
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Ceccherini, S., U. Cortesi, P. T. Verronen, and E. Kyrölä. "Technical Note: Continuity of MIPAS-ENVISAT operational ozone data quality from full- to reduced-spectral-resolution operation mode." Atmospheric Chemistry and Physics 8, no. 8 (April 21, 2008): 2201–12. http://dx.doi.org/10.5194/acp-8-2201-2008.
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Abstract. MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) is operating on the ENVIronmental SATellite (ENVISAT) since March 2002. After two years of nearly continuous limb scanning measurements, at the end of March 2004, the instrument was stopped due to problems with the mirror drive of the interferometer. Operations with reduced maximum path difference, corresponding to both a reduced-spectral-resolution and a shorter measurement time, were resumed on January 2005. In order to exploit the reduction in measurement time, the measurement scenario was changed adopting a finer vertical limb scanning. The change of spectral resolution and of measurement scenario entailed an update of the data processing strategy. The aim of this paper is the assessment of the differences in the quality of the MIPAS ozone data acquired before and after the stop of the operations. Two sets of MIPAS ozone profiles acquired in 2003–2004 (full-resolution measurements) and in 2005–2006 (reduced-resolution measurements) are compared with collocated ozone profiles obtained by GOMOS (Global Ozone Monitoring by Occultation of Stars), itself also onboard ENVISAT. The continuity of the GOMOS data quality allows to assess a possible discontinuity of the MIPAS performances. The relative bias and precision of MIPAS ozone profiles with respect to the GOMOS ones have been compared for the measurements acquired before and after the stop of the MIPAS operations. The results of the comparison show that, in general, the quality of the MIPAS ozone profiles retrieved from reduced-resolution measurements is comparable or better than that obtained from the full-resolution dataset. The only significant change in MIPAS performances is observed at pressures around 2 hPa, where the relative bias of the instruments increases by a factor of 2 from the 2003–2004 to 2005–2006 measurements.
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Fischer, H., M. Birk, C. Blom, B. Carli, M. Carlotti, T. von Clarmann, L. Delbouille, et al. "MIPAS: an instrument for atmospheric and climate research." Atmospheric Chemistry and Physics 8, no. 8 (April 16, 2008): 2151–88. http://dx.doi.org/10.5194/acp-8-2151-2008.
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Abstract. MIPAS, the Michelson Interferometer for Passive Atmospheric Sounding, is a mid-infrared emission spectrometer which is part of the core payload of ENVISAT. It is a limb sounder, i.e. it scans across the horizon detecting atmospheric spectral radiances which are inverted to vertical temperature, trace species and cloud distributions. These data can be used for scientific investigations in various research fields including dynamics and chemistry in the altitude region between upper troposphere and lower thermosphere. The instrument is a well calibrated and characterized Fourier transform spectrometer which is able to detect many trace constituents simultaneously. The different concepts of retrieval methods are described including multi-target and two-dimensional retrievals. Operationally generated data sets consist of temperature, H2O, O3, CH4, N2O, HNO3, and NO2 profiles. Measurement errors are investigated in detail and random and systematic errors are specified. The results are validated by independent instrumentation which has been operated at ground stations or aboard balloon gondolas and aircraft. Intercomparisons of MIPAS measurements with other satellite data have been carried out, too. As a result, it has been proven that the MIPAS data are of good quality. MIPAS can be operated in different measurement modes in order to optimize the scientific output. Due to the wealth of information in the MIPAS spectra, many scientific results have already been published. They include intercomparisons of temperature distributions with ECMWF data, the derivation of the whole NOy family, the study of atmospheric processes during the Antarctic vortex split in September~2002, the determination of properties of Polar Stratospheric Clouds, the downward transport of NOx in the middle atmosphere, the stratosphere-troposphere exchange, the influence of solar variability on the middle atmosphere, and the observation of Non-LTE effects in the mesosphere.
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Fischer, H., M. Birk, C. Blom, B. Carli, M. Carlotti, T. von Clarmann, L. Delbouille, et al. "MIPAS: an instrument for atmospheric and climate research." Atmospheric Chemistry and Physics Discussions 7, no. 3 (June 25, 2007): 8795–893. http://dx.doi.org/10.5194/acpd-7-8795-2007.
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Abstract. MIPAS, the Michelson Interferometer for Passive Atmospheric Sounding, is a mid-infrared emission spectrometer which is part of the core payload of ENVISAT. It is a limb sounder, i.e. it scans across the horizon detecting atmospheric spectral radiances which are inverted to vertical temperature, trace species and cloud distributions. These data can be used for scientific investigations in various research fields including dynamics and chemistry in the altitude region between upper troposphere and lower thermosphere. The instrument is a well calibrated and characterized Fourier transform spectrometer which is able to detect many trace constituents simultaneously. The different concepts of retrieval methods are described including multi-target and two-dimensional retrievals. Operationally generated data sets consist of temperature, H2O, O3, CH4, N2O, HNO3, and NO2 profiles. Measurement errors are investigated in detail and random and systematic errors are specified. The results are validated by independent instrumentation which has been operated at ground stations or aboard balloon gondolas and aircraft. Intercomparisons of MIPAS measurements with other satellite data have been carried out, too. As a result, it has been proven that the MIPAS data are of good quality. MIPAS can be operated in different measurement modes in order to optimize the scientific output. Due to the wealth of information in the MIPAS spectra, many scientific results have already been published. They include intercomparisons of temperature distributions with ECMWF data, the derivation of the whole NOy family, the study of atmospheric processes during the Antarctic vortex split in September 2002, the determination of properties of Polar Stratospheric Clouds, the downward transport of NOx in the middle atmosphere, the stratosphere-troposphere exchange, the influence of solar variability on the middle atmosphere, and the observation of Non-LTE effects in the mesosphere.
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Hurley, J., A. Dudhia, and R. G. Grainger. "Cloud detection for MIPAS using singular vector decomposition." Atmospheric Measurement Techniques Discussions 2, no. 2 (April 29, 2009): 1185–219. http://dx.doi.org/10.5194/amtd-2-1185-2009.
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Abstract. Clouds are increasingly recognised for their influence on the radiative balance of the Earth and the implications that they have on possible climate change, as well as in air pollution and acid-rain production. However, clouds remain a major source of uncertainty in climate models. Satellite-borne high-resolution limb sounders, such as the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) onboard ENVISAT, provide information on clouds, especially optically thin clouds, which have been difficult to observe in the past. The aim of this work is to develop, implement and test a reliable cloud detection method for infrared spectra measured by MIPAS. Current MIPAS cloud detection methods used operationally have been developed to detect thick cloud filling more than 30% of the measurement field-of-view (FOV). In order to resolve thin clouds, a new detection method using Singular Vector Decomposition (SVD) is formulated and tested. A rigorous comparison of the current operational and newly-developed detection methods for MIPAS is carried out – and the new SVD detection method has been proven to be much more reliable than the current operational method, and very sensitive even to thin clouds only marginally filling the MIPAS FOV.
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López-Puertas, Manuel, Bernd Funke, Sergio Gil-López, Miguel Á. López-Valverde, Thomas von Clarmann, Herbert Fischer, Hermann Oelhaf, et al. "Atmospheric non-local thermodynamic equilibrium emissions as observed by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS)." Comptes Rendus Physique 6, no. 8 (October 2005): 848–63. http://dx.doi.org/10.1016/j.crhy.2005.07.012.
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Woiwode, W., H. Oelhaf, T. Gulde, C. Piesch, G. Maucher, A. Ebersoldt, C. Keim, et al. "MIPAS-STR measurements in the Arctic UTLS in winter/spring 2010: instrument characterization, retrieval and validation." Atmospheric Measurement Techniques 5, no. 6 (June 1, 2012): 1205–28. http://dx.doi.org/10.5194/amt-5-1205-2012.
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Abstract. The mid-infrared FTIR-limb-sounder Michelson Interferometer for Passive Atmospheric Sounding–STRatospheric aircraft (MIPAS-STR) was deployed onboard the research aircraft M55 Geophysica during the RECONCILE campaign (Reconciliation of Essential Process Parameters for an Enhanced Predictability of Arctic Stratospheric Ozone Loss and its Climate Interactions) in the Arctic winter/spring 2010. From the MIPAS-STR measurements, vertical profiles and 2-dimensional vertical cross-sections of temperature and trace gases are retrieved. Detailed mesoscale structures of polar vortex air, extra vortex air and vortex filaments are identified in the results at typical vertical resolutions of 1 to 2 km and typical horizontal sampling densities of 45 or 25 km, depending on the sampling programme. Results are shown for the RECONCILE flight 11 on 2 March 2010 and are validated with collocated in-situ measurements of temperature, O3, CFC-11, CFC-12 and H2O. Exceptional agreement is found for the in-situ comparisons of temperature and O3, with mean differences (vertical profile/along flight track) of 0.2/−0.2 K for temperature and −0.01/0.05 ppmv for O3 and corresponding sample standard deviations of the mean differences of 0.7/0.6 K and 0.1/0.3 ppmv. The comparison of the retrieved vertical cross-sections of HNO3 from MIPAS-STR and the infrared limb-sounder Cryogenic Infrared Spectrometers and Telescopes for the Atmosphere–New Frontiers (CRISTA–NF) indicates a high degree of agreement. We discuss MIPAS-STR in its current configuration, the spectral and radiometric calibration of the measurements and the retrieval of atmospheric parameters from the spectra. The MIPAS-STR measurements are significantly affected by continuum-like contributions, which are attributed to background aerosol and broad spectral signatures from interfering trace gases, and are important for mid-infrared limb-sounding in the Upper Troposphere/Lower Stratosphere (UTLS) region. Taking into consideration continuum-like effects, we present a scheme suitable for accurate retrievals of temperature and an extended set of trace gases, including the correction of a systematic line-of-sight offset.
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von Clarmann, T., B. Funke, N. Glatthor, S. Kellmann, M. Kiefer, O. Kirner, B. M. Sinnhuber, and G. P. Stiller. "The MIPAS HOCl climatology." Atmospheric Chemistry and Physics 12, no. 4 (February 20, 2012): 1965–77. http://dx.doi.org/10.5194/acp-12-1965-2012.
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Abstract. Monthly zonal mean HOCl measurements by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) are presented for the period from June 2002 to March 2004. Highest molar mixing ratios are found at pressure levels between 6 and 2 hPa, whereby largest mixing ratios occasionally exceed 200 ppt. The mixing ratio maximum is generally higher at lower altitudes in the summer hemisphere than in the winter hemisphere except for chlorine activation conditions in polar vortices, where enhanced HOCl abundances are also found in the lower stratosphere below about 10 hPa. During nighttime the maximum is found at higher altitudes than during daytime. Particularly low values (below 80 ppt) during daytime are found in subpolar regions in the winter hemisphere where HOCl photolysis is still strong but where HOCl precursors are less abundant than at other latitudes. The Antarctic polar winter HOCl distribution in 2002, the year of the split of the southern polar vortex, resembles northern polar winters rather than other southern polar winters. Increased HOCl amounts in response to the so-called Halloween solar proton event in autumn 2003 affect the representativeness of data recorded during this particular episode. Calculations with the EMAC model reproduce the measured HOCl distribution reasonably well. MIPAS measurements confirm that the reaction rate constants for HO2 + ClO &longrightarrow; HOCl + O2 from the most recent JPL recommendation allow much more realistic modelling of HOCl than reaction rate constants from earlier recommendations. Modeled HOCl mixing ratios, however, are still too low except in the polar winter stratosphere where the model overestimates the HOCl abundance.
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Höpfner, M., N. Larsen, R. Spang, B. P. Luo, J. Ma, S. H. Svendsen, S. D. Eckermann, et al. "MIPAS detects Antarctic stratospheric belt of NAT PSCs caused by mountain waves." Atmospheric Chemistry and Physics 6, no. 5 (April 20, 2006): 1221–30. http://dx.doi.org/10.5194/acp-6-1221-2006.
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Abstract. Space borne infrared limb emission measurements by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) reveal the formation of a belt of polar stratospheric clouds (PSCs) of nitric acid trihydrate (NAT) particles over Antarctica in mid-June 2003. By mesoscale microphysical simulations we show that this sudden onset of NAT PSCs was caused by heterogeneous nucleation on ice in the cooling phases of large-amplitude stratospheric mountain waves over the Antarctic Peninsula and the Ellsworth Mountains. MIPAS observations of PSCs before this event show no indication for the presence of NAT clouds with volume densities larger than about 0.3 µm3/cm3 and radii smaller than 3 µm, but are consistent with supercooled droplets of ternary H2SO4/HNO3/H2O solution (STS). Simulations indicate that homogeneous surface nucleation rates have to be reduced by three orders of magnitude to comply with the observations.
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Steck, T., T. von Clarmann, H. Fischer, B. Funke, N. Glatthor, U. Grabowski, M. Höpfner, et al. "Bias determination and precision validation of ozone profiles from MIPAS-Envisat retrieved with the IMK-IAA processor." Atmospheric Chemistry and Physics 7, no. 13 (July 11, 2007): 3639–62. http://dx.doi.org/10.5194/acp-7-3639-2007.
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Abstract. This paper characterizes vertical ozone profiles retrieved with the IMK-IAA (Institute for Meteorology and Climate Research, Karlsruhe – Instituto de Astrofisica de Andalucia) science-oriented processor from high spectral resolution data (until March 2004) measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) aboard the environmental satellite Envisat. Bias determination and precision validation is performed on the basis of correlative measurements by ground-based lidars, Fourier transform infrared spectrometers, and microwave radiometers as well as balloon-borne ozonesondes, the balloon-borne version of MIPAS, and two satellite instruments (Halogen Occultation Experiment and Polar Ozone and Aerosol Measurement III). Percentage mean differences between MIPAS and the comparison instruments for stratospheric ozone are generally within ±10%. The precision in this altitude region is estimated at values between 5 and 10% which gives an accuracy of 15 to 20%. Below 18 km, the spread of the percentage mean differences is larger and the precision degrades to values of more than 20% depending on altitude and latitude. The main reason for the degraded precision at low altitudes is attributed to undetected thin clouds which affect MIPAS retrievals, and to the influence of uncertainties in the water vapor concentration.
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Höpfner, M., B. P. Luo, P. Massoli, F. Cairo, R. Spang, M. Snels, G. Di Donfrancesco, et al. "Spectroscopic evidence for NAT, STS, and ice in MIPAS infrared limb emission measurements of polar stratospheric clouds." Atmospheric Chemistry and Physics 6, no. 5 (April 20, 2006): 1201–19. http://dx.doi.org/10.5194/acp-6-1201-2006.
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Abstract. We have analyzed mid-infrared limb-emission measurements of polar stratospheric clouds (PSCs) by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) during the Antarctic winter 2003 with respect to PSC composition. Coincident Lidar observations from McMurdo were used for comparison with PSC types 1a, 1b and 2. Application of new refractive index data of β-NAT have allowed to accurately simulate the prominent spectral band at 820 cm-1 observed by MIPAS at the location where the Lidar instrument observed type 1a PSCs. Broadband spectral fits covering the range from 780 to 960 cm-1 and from 1220 to 1490 cm-1 showed best agreement with the MIPAS measurements when spectroscopic data of NAT were used to simulate the MIPAS spectra. MIPAS measurements collocated with Lidar observations of Type 1b and Type 2 PSCs could only be reproduced by assuming a composition of supercooled ternary H2SO4/HNO3/H2O solution (STS) and of ice, respectively. Particle radius and number density profiles derived from MIPAS were generally consistent with the Lidar observations. Only in the case of ice clouds, PSC volumes are partly underestimated by MIPAS due to large cloud optical thickness in the limb-direction. A comparison of MIPAS cloud composition and Lidar PSC-type determination based on all available MIPAS-Lidar coincident measurements revealed good agreement between PSC-types 1a, 1b and 2, and NAT, STS and ice, respectively. We could not find spectroscopic evidence for the presence of nitric acid dihydrate (NAD) from MIPAS observations of PSCs over Antarctica in 2003.
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Friedl-Vallon, Felix, Guido Maucher, Meinhard Seefeldner, Olaf Trieschmann, Anne Kleinert, Anton Lengel, Corneli Keim, Hermann Oelhaf, and Herbert Fischer. "Design and characterization of the balloon-borne Michelson Interferometer for Passive Atmospheric Sounding (MIPAS-B2)." Applied Optics 43, no. 16 (June 1, 2004): 3335. http://dx.doi.org/10.1364/ao.43.003335.
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Sembhi, H., J. Remedios, T. Trent, D. P. Moore, R. Spang, S. Massie, and J. P. Vernier. "MIPAS detection of cloud and aerosol particle occurrence in the UTLS with comparison to HIRDLS and CALIOP." Atmospheric Measurement Techniques 5, no. 10 (October 26, 2012): 2537–53. http://dx.doi.org/10.5194/amt-5-2537-2012.
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Abstract. Satellite infrared emission instruments require efficient systems that can separate and flag observations which are affected by clouds and aerosols. This paper investigates the identification of cloud and aerosols from infrared, limb sounding spectra that were recorded by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), a high spectral resolution Fourier transform spectrometer on the European Space Agency's (ESA) ENVISAT (Now inoperative since April 2012 due to loss of contact). Specifically, the performance of an existing cloud and aerosol particle detection method is simulated with a radiative transfer model in order to establish, for the first time, confident detection limits for particle presence in the atmosphere from MIPAS data. The newly established thresholds improve confidence in the ability to detect particle injection events, plume transport in the upper troposphere and lower stratosphere (UTLS) and better characterise cloud distributions utilising MIPAS spectra. The method also provides a fast front-end detection system for the MIPClouds processor; a processor designed for the retrieval of macro- and microphysical cloud properties from the MIPAS data. It is shown that across much of the stratosphere, the threshold for the standard cloud index in band A is 5.0 although threshold values of over 6.0 occur in restricted regimes. Polar regions show a surprising degree of uncertainty at altitudes above 20 km, potentially due to changing stratospheric trace gas concentrations in polar vortex conditions and poor signal-to-noise due to cold atmospheric temperatures. The optimised thresholds of this study can be used for much of the time, but time/composition-dependent thresholds are recommended for MIPAS data for the strongly perturbed polar stratosphere. In the UT, a threshold of 5.0 applies at 12 km and above but decreases rapidly at lower altitudes. The new thresholds are shown to allow much more sensitive detection of particle distributions in the UTLS, with extinction detection limits above 13 km often better than 10−4 km−1, with values approaching 10−5 km−1 in some cases. Comparisons of the new MIPAS results with cloud data from HIRDLS and CALIOP, outside of the poles, establish a good agreement in distributions (cloud and aerosol top heights and occurrence frequencies) with an offset between MIPAS and the other instruments of 0.5 km to 1 km between 12 km and 20 km, consistent with vertical oversampling of extended cloud layers within the MIPAS field of view. We conclude that infrared limb sounders provide a very consistent picture of particles in the UTLS, allowing detection limits which are consistent with the lidar observations. Investigations of MIPAS data for the Mount Kasatochi volcanic eruption on the Aleutian Islands and the Black Saturday fires in Australia are used to exemplify how useful MIPAS limb sounding data were for monitoring aerosol injections into the UTLS. It is shown that the new thresholds allowed such events to be much more effectively derived from MIPAS with detection limits for these case studies of 1 × 10−5 km−1 at a wavelength of 12 μm.
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Hervig, Mark E., Benjamin T. Marshall, Scott M. Bailey, David E. Siskind, James M. Russell III, Charles G. Bardeen, Kaley A. Walker, and Bernd Funke. "Validation of Solar Occultation for Ice Experiment (SOFIE) nitric oxide measurements." Atmospheric Measurement Techniques 12, no. 6 (June 13, 2019): 3111–21. http://dx.doi.org/10.5194/amt-12-3111-2019.
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Abstract. Nitric oxide (NO) measurements from the Solar Occultation for Ice Experiment (SOFIE) are validated through detailed uncertainty analysis and comparisons with independent observations. SOFIE was compared with coincident satellite measurements from the Atmospheric Chemistry Experiment (ACE) – Fourier Transform Spectrometer (FTS) instrument and the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument. The comparisons indicate mean differences of less than ∼50 % for altitudes from roughly 50 to 105 km for SOFIE spacecraft sunrise and 50 to 140 km for SOFIE sunsets. Comparisons of NO time series show a high degree of correlation between SOFIE and both ACE and MIPAS for altitudes below ∼130 km, indicating that measured NO variability in time is robust. SOFIE uncertainties increase below ∼80 km due to interfering H2O absorption and signal correction uncertainties, which are larger for spacecraft sunrise compared to sunset. These errors are sufficiently large in sunrises that reliable NO measurements are infrequent below ∼80 km.
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Remedios, J. J., R. J. Leigh, A. M. Waterfall, D. P. Moore, H. Sembhi, I. Parkes, J. Greenhough, M. P. Chipperfield, and D. Hauglustaine. "MIPAS reference atmospheres and comparisons to V4.61/V4.62 MIPAS level 2 geophysical data sets." Atmospheric Chemistry and Physics Discussions 7, no. 4 (July 10, 2007): 9973–10017. http://dx.doi.org/10.5194/acpd-7-9973-2007.
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Abstract. Reliable reference profiles and estimates of variability are a necessity for a variety of processes relating to ENVISAT including the development of key aspects and inputs for the operational processor for the Michelson Interferometer for Passive Atmospheric Sounding. MIPAS reference atmospheres have therefore been produced in two forms, namely standard atmospheres for modelling and error analysis for typical atmospheric situations and the IG2 seasonal climatologies for initial guess profiles used as part of the operational processing. The reference states cover 36 species on a common altitude, pressure, and temperature grid from 0 to 120 km, and include both means and estimates of variability (maximum, minimum and one sigma values). This paper describes V3.1 of the standard atmospheres and V4.0 of the IG2 atmospheres which are the current versions of the reference atmospheres. Particular attention is paid to the MIPAS operational geophysical products (pressure/temperature, H2O, O3, CH4, N2O, HNO3 and NO2) and to CO2 whose mixing ratio is required for the retrieval of pressure and temperature. A dynamic representation of CO2 is presented which shows the presence of CO2 gradients in the troposphere and the lower stratosphere. Since these atmospheres have been produced independently of MIPAS data, it is also possible to compare the data to the MIPAS operational products and derive valuable information on both the reference atmospheres and on MIPAS data products themselves. This process has been performed for V4.61/V4.62 data from the year 2003 as part of the MIPAS validation activity. It is demonstrated that the agreement between the MIPAS mean data and the reference atmospheres is very good in mid-latitudes and the tropics, verifying these data to first order. There is also reasonable agreement in standard deviations between the IG2 atmospheres and the corresponding sigmas calculated from the MIPAS data. Knowledge of tropospheric concentrations of CH4 and N2O is used to examine the accuracy of the MIPAS data and their susceptibility to cloud effects. It is shown that for the highest accuracy, MIPAS data should be filtered with cloud index values of 2.5 for N2O and 3.5 for CH4. Once such filtering has been performed, the MIPAS data for these species appear to be accurate to within 10% in the upper troposphere. The use of cloud index data in combination with MIPAS data is recommended for studies of the polar winter stratosphere and the upper troposphere/lower stratosphere.
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von Clarmann, T., B. Funke, N. Glatthor, S. Kellmann, M. Kiefer, O. Kirner, B. M. Sinnhuber, and G. P. Stiller. "The MIPAS HOCl climatology." Atmospheric Chemistry and Physics Discussions 11, no. 7 (July 22, 2011): 20793–822. http://dx.doi.org/10.5194/acpd-11-20793-2011.
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Abstract. Monthly zonal mean HOCl measurements by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) are presented for the episode from June 2002 to March 2004. Highest molar mixing ratios are found at pressure levels between 6 and 2 hPa, whereby largest mixing ratios occasionally exceed 200 ppt. The mixing ratio maximum is generally at lower altitudes in the summer hemisphere than in the winter hemisphere except for chlorine activation conditions in polar vortices, where enhanced HOCl abundances are also found in the lower stratosphere. During nighttime the maximum is found at higher altitudes than during daytime. Particularly low values are found in subpolar regions in the winter hemisphere, coinciding with the mixing barrier formed by the polar vortex boundary. The Antarctic polar winter HOCl distribution in 2002, the year of the split of the southern polar vortex, resembles northern polar winters rather than other southern polar winters. Increased HOCl amounts in response to the so-called Halloween solar proton event in autumn 2003 affect the representativeness of data recorded during this particular episode. Calculations with the EMAC model reproduce the structure of the measured HOCl distribution but predict approximately 40 % less HOCl except during polar night in the mid-stratosphere where calculated HOCl mixing ratios exceed observed ones.
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Sembhi, H., J. Remedios, T. Trent, D. P. Moore, R. Spang, S. Massie, and J. P. Vernier. "MIPAS detection of cloud and aerosol particle occurrence in the UTLS with comparison to HIRDLS and CALIOP." Atmospheric Measurement Techniques Discussions 5, no. 1 (February 22, 2012): 1795–841. http://dx.doi.org/10.5194/amtd-5-1795-2012.
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Abstract. Satellite infra-red emission instruments require efficient systems that can separate and flag observations which are affected by clouds and aerosols. This paper investigates the identification of cloud and aerosols from infra-red, limb sounding spectra recorded by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS), a high spectral resolution, Fourier transform spectrometer on ENVISAT. Specifically, the performance of an existing cloud and aerosol particle detection method is simulated, with a radiative transfer model, in order to establish for the first time limits to confident detection of particle effects in MIPAS data. The newly established thresholds improve confidence in the ability of MIPAS to detect particle injection events and plume transport in the UTLS as well as better characterised cloud distributions. The method also provides a fast front-end detection system for the MIPClouds processor, a processor designed for the retrieval of macro- and microphysical cloud properties from the MIPAS data. It is shown that across much of the stratosphere, the threshold for the standard cloud index in band A is 5 although values of greater than 6 occur in restricted regimes. Polar regions show a surprising degree of uncertainty at altitudes above 20 km due to potential high ClO formation and also poor signal-to-noise due to low atmosphere temperatures. The optimised thresholds of this study can be used for much of the time, but time/composition dependent thresholds are recommended for MIPAS data for the strongly perturbed polar stratosphere. In the UT, thresholds of 5 apply at 12 km and above but decrease rapidly at lower altitudes. The new thresholds are shown to allow much more sensitive detection of particle distributions in the upper troposphere and lower stratosphere (UTLS), with extinction detection limits above 13 km often better than 10−4 km−1, with values approaching 10−5 km−1 in some cases. Comparisons of the new MIPAS results with data from HIRDLS and CALIOP, outside of the poles, establishes good agreement in distributions (cloud occurrence frequencies and clouds and aerosol top heights) with an offset between MIPAS and the other instruments of 0.5 km between 12 and 20 km. We conclude that current infra-red limb sounders provide a very consistent picture of particles in the UTLS, allowing detection limits which are consistent with the lidar observations. Investigations of the MIPAS data for the Kasatochi volcanic eruption and the Black Saturday fires in Australia are used to exemplify the usefulness of MIPAS limb sounding data for monitoring aerosol injections into the UTLS, and into the stratosphere, in particular over monthly timescales. It is shown that the new thresholds allow such events to be much more effectively monitored from MIPAS with detection limits for these case studies of 1 × 10−5 km−1 at 12 μm.
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Woiwode, W., O. Sumińska-Ebersoldt, H. Oelhaf, M. Höpfner, G. V. Belyaev, A. Ebersoldt, F. Friedl-Vallon, et al. "Validation of first chemistry mode retrieval results from the new limb-imaging FTS GLORIA with correlative MIPAS-STR observations." Atmospheric Measurement Techniques 8, no. 6 (June 19, 2015): 2509–20. http://dx.doi.org/10.5194/amt-8-2509-2015.
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Abstract. We report first chemistry mode retrieval results from the new airborne limb-imaging infrared FTS (Fourier transform spectrometer) GLORIA (Gimballed Limb Observer for Radiance Imaging of the Atmosphere) and comparisons with observations by the conventional airborne limb-scanning infrared FTS MIPAS-STR (Michelson Interferometer for Passive Atmospheric Sounding – STRatospheric aircraft). For GLORIA, the flights aboard the high-altitude research aircraft M55 Geophysica during the ESSenCe campaign (ESa Sounder Campaign 2011) were the very first in field deployment after several years of development. The simultaneous observations of GLORIA and MIPAS-STR during the flight on 16 December 2011 inside the polar vortex and under conditions of optically partially transparent polar stratospheric clouds (PSCs) provided us the first opportunity to compare the observations by two different infrared FTS generations directly. We validate the GLORIA results with MIPAS-STR based on the lower vertical resolution of MIPAS-STR and compare the vertical resolutions of the instruments derived from their averaging kernels. The retrieval results of temperature, HNO3, O3, H2O, CFC-11 and CFC-12 show reasonable agreement of GLORIA with MIPAS-STR and collocated in situ observations. For the horizontally binned hyperspectral limb images, the GLORIA sampling outnumbered the horizontal cross-track sampling of MIPAS-STR by up to 1 order of magnitude. Depending on the target parameter, typical vertical resolutions of 0.5 to 2.0 km were obtained for GLORIA and are typically a factor of 2 to 4 better compared to MIPAS-STR. While the improvement of the performance, characterization and data processing of GLORIA are the subject of ongoing work, the presented first results already demonstrate the considerable gain in sampling and vertical resolution achieved with GLORIA.
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Griessbach, S., L. Hoffmann, R. Spang, and M. Riese. "Volcanic ash detection with infrared limb sounding: MIPAS observations and radiative transfer simulations." Atmospheric Measurement Techniques Discussions 6, no. 6 (November 15, 2013): 9939–91. http://dx.doi.org/10.5194/amtd-6-9939-2013.
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Abstract. Small volcanic ash particles have long residence times in troposphere and stratosphere so that they have impact on the Earth's radiative budget and consequently affect climate. For global long term observations of volcanic aerosol, infrared limb measurements provide excellent coverage, sensitivity to thin aerosol layers, and altitude information. The optical properties of volcanic ash and ice particles, derived from micro-physical properties, have opposing spectral gradients between 700 to 960 cm−1 for small particle sizes. Radiative transfer simulations that account for single scattering showed that the opposing spectral gradients directly transfer to infrared limb spectra. Indeed, we found the characteristic spectral signature, expected for volcanic ash, in measurements of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) after the eruption of the Chilean volcano Puyehue-Cordón Caulle in June 2011. From these measurements we derived an ash detection threshold function. The empirical ash detection threshold was confirmed by simulations covering a wide range of atmospheric conditions, particle sizes, and particle concentrations for ice, volcanic ash, and sulfate aerosol. From the simulations we derived the detectable effective radius range of 0.2 to 3.5 μm and the detectable extinction coefficient range of 5 × 10−3 to 1 × 10−1 km−1. We also showed that this method is only sensitive to volcanic ash particles, but not to volcanic sulfate aerosol. This volcanic ash detection method for infrared limb measurements is a fast and reliable method and provides complementary information to existing satellite aerosol products.
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von Clarmann, T., C. De Clercq, M. Ridolfi, M. Höpfner, and J. C. Lambert. "The horizontal resolution of MIPAS." Atmospheric Measurement Techniques 2, no. 1 (February 18, 2009): 47–54. http://dx.doi.org/10.5194/amt-2-47-2009.
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Abstract. Limb remote sensing from space provides atmospheric composition measurements at high vertical resolution while the information is smeared in the horizontal domain. The horizontal components of two-dimensional (altitude and along-track coordinate) averaging kernels of a limb retrieval constrained to horizontal homogeneity can be used to estimate the horizontal resolution of limb retrievals. This is useful for comparisons of measured data with modeled data, to construct horizontal observation operators in data assimilation applications or when measurements of different horizontal resolution are intercompared. We present these averaging kernels for retrievals of temperature, H2O, O3, CH4, N2O, HNO3 and NO2 from MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) high-resolution limb emission spectra. The horizontal smearing of a MIPAS retrieval in terms of full width at half maximum of the rows of the horizontal averaging kernel matrix varies typically between about 200 and 350 km for most species, altitudes and atmospheric conditions. The range where 95% of the information originates from varies from about 260 to 440 km for these cases. This information spread is smaller than the MIPAS horizontal sampling, i.e. MIPAS data are horizontally undersampled, and the effective horizontal resolution is driven by the sampling rather than the smearing. The point where the majority of the information originates from is displaced from the tangent point towards the satellite by typically less than 10 km for trace gas profiles and about 50 to 100 km for temperature, with a few exceptions for uppermost altitudes. The geolocation of a MIPAS profile is defined as the tangent point of the middle line of sight in a MIPAS limb scan. The majority of the information displacement with respect to this nominal geolocation of the measurement is caused by the satellite movement and the geometrical displacement of the actual tangent point as a function of the elevation angle.
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Moore, D. P., and J. J. Remedios. "Growth rates of stratospheric HCFC-22." Atmospheric Chemistry and Physics 8, no. 1 (January 14, 2008): 73–82. http://dx.doi.org/10.5194/acp-8-73-2008.
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Abstract. The Michelson Interferometer for Passive Atmospheric Sounding onboard ENVISAT (MIPAS-E) offers the opportunity to detect and spectrally resolve many atmospheric minor constituents affecting atmospheric chemistry. In this paper, we describe an algorithm produced to retrieve HCFC–22 profiles from MIPAS-E measurements made in 2003 and present results from this scheme between 300 and 50 mb. By comparison with ATMOS (AT–3) version 3 data, we find a mean Northern Hemisphere mid-latitude (20–50° N) HCFC–22 growth rate between 1994 and 2003 of 5.4±0.7 pptv/yr in the lower stratosphere (LS) and a mean LS Southern Hemisphere growth rate (60–80° S) of 6.0±0.7 pptv/yr in the same period. We test the feasibility of using a global data set to estimate the chemical lifetime of HCFC–22 in the LS and we derive this for two regions: 20–50° N (246±38 years) and 60–80° S (274±34 years). From these data we note a global LS lifetime of 260±25 years, significantly longer than previous estimates.
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Bender, S., M. Sinnhuber, J. P. Burrows, M. Langowski, B. Funke, and M. López-Puertas. "Retrieval of nitric oxide in the mesosphere and lower thermosphere with SCIAMACHY." Atmospheric Measurement Techniques Discussions 6, no. 2 (April 12, 2013): 3611–42. http://dx.doi.org/10.5194/amtd-6-3611-2013.
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Abstract. We use the ultra-violett (UV) spectra in the range 230–300 nm from the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) to retrieve the nitric oxide (NO) number densities from atmospheric emissions in the gamma-bands in the mesosphere and lower thermosphere. Using 3-D ray tracing, a 2-D retrieval grid, and regularisation with respect to altitude and latitude, we retrieve a whole semi-orbit simultaneously for the altitude range from 60 to 160 km. We present details of the retrieval algorithm, first results, and initial comparisons to data from the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS). Our results agree on average well with MIPAS data and are compatible with previously published measurements from other instruments. For the time of available measurements in 2008–2011, we achieve a vertical resolution of 5–10 km in the altitude range 70–140 km and a horizontal resolution of about 9° from 60° S–60° N. With this we have independent measurements of the NO densities in the mesosphere and lower thermosphere with approximately global coverage.
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von Clarmann, T., N. Glatthor, G. P. Stiller, U. Grabowski, M. Höpfner, S. Kellmann, A. Linden, et al. "MIPAS measurements of upper tropospheric C<sub>2</sub>H<sub>6</sub> and O<sub>3</sub> during the Southern hemispheric biomass burning season in 2003." Atmospheric Chemistry and Physics Discussions 7, no. 4 (August 15, 2007): 12067–95. http://dx.doi.org/10.5194/acpd-7-12067-2007.
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Abstract. Under cloud free conditions, the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) provides measurements of spectrally resolved limb radiances down to the upper troposphere. These are used to infer global distributions of mixing ratios of atmospheric constituents in the upper troposphere and the stratosphere. From 21 October to 14 November 2003, MIPAS observed enhanced amounts of upper tropospheric C2H6 (up to about 400 pptv, depending on spectroscopic data chosen) and ozone (up to about 80 ppbv). By means of trajectory calculations, the enhancements observed in the Southern hemisphere are, at least partly, attributed to a biomass burning plume, which covers wide parts of the Southern hemisphere, from South America, the Atlantic ocean, Africa, the Indian Ocean to Australia. The chemical composition of the part of the plume-like pollution belt associated with South American rainforest burning appears different from the part associated with Southern African savanna burning. In particular, African savanna fires lead to a larger ozone enhancement than South American rainforest fires.
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Plieninger, J., A. Laeng, S. Lossow, T. von Clarmann, G. P. Stiller, S. Kellmann, A. Linden, et al. "Validation of revised methane and nitrous oxide profiles from MIPAS-ENVISAT." Atmospheric Measurement Techniques Discussions 8, no. 11 (November 20, 2015): 12105–53. http://dx.doi.org/10.5194/amtd-8-12105-2015.
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Abstract. Improved versions of CH4 and N2O profiles derived at the Institute of Meteorology and Climate Research and Instituto de Astrofísica de Andalucía (CSIC) from spectra measured by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) have become available. For the MIPAS full resolution period (2002–2004) these are V5H_CH4_21 and V5H_N2O_21 and for the reduced resolution period (2005–2012) these are V5R_CH4_224, V5R_CH4_225, V5R_N2O_224 and V5R_N2O_225. Here, we compare CH4 profiles to those measured by the Fourier Transform Spectrometer on board of the Atmospheric Chemistry Experiment (ACE-FTS), the HALogen Occultation Experiment (HALOE) and the Scanning Imaging Absorption Spectrometer for Atmospheric CHartographY (SCIAMACHY) and to the Global Cooperative Air Sampling Network (GCASN) surface data. We find the MIPAS CH4 profiles below 25 km to be typically higher in the order of 0.1 ppmv for both measurement periods. N2O profiles are compared to those measured by ACE-FTS, the Microwave Limb Sounder on board of the Aura satellite (Aura-MLS) and the Sub-millimetre Radiometer on board of the Odin satellite (Odin-SMR) as well as to the Halocarbons and other Atmospheric Trace Species Group (HATS) surface data. The mixing ratios from the satellite instruments agree well for the full resolution period. For the reduced resolution period, MIPAS produces similar values as Odin-SMR, but higher values than ACE-FTS and HATS. Below 27 km, the MIPAS profiles show higher mixing ratios than Aura-MLS, and lower values between 27 and 41 km. Cross comparisons between the two MIPAS measurement periods show that they generally agree quite well, but, especially for CH4, the reduced resolution period seems to produce slightly higher mixing ratios than the full resolution data.
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Griessbach, S., L. Hoffmann, R. Spang, and M. Riese. "Volcanic ash detection with infrared limb sounding: MIPAS observations and radiative transfer simulations." Atmospheric Measurement Techniques 7, no. 5 (May 28, 2014): 1487–507. http://dx.doi.org/10.5194/amt-7-1487-2014.
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Abstract. Small volcanic ash particles have long residence times in the troposphere and the stratosphere so that they have significant impact on the Earth's radiative budget and consequently affect climate. For global long-term observations of volcanic aerosol, infrared limb measurements provide excellent coverage, sensitivity to thin aerosol layers, and altitude information. The optical properties of volcanic ash and ice particles, derived from micro-physical properties, have opposing spectral gradients between 700 and 960 cm−1 for small particle sizes. Radiative transfer simulations that account for single scattering showed that the opposing spectral gradients directly transfer to infrared limb spectra. Indeed, we found the characteristic spectral signature, expected for volcanic ash, in measurements of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) after the eruption of the Chilean volcano Puyehue-Cordón Caulle in June 2011. From these measurements we derived an ash detection threshold function. The empirical ash detection threshold was confirmed in an extensive simulations study covering a wide range of atmospheric conditions, particle sizes and particle concentrations for ice, volcanic ash and sulfate aerosol. From the simulations we derived the upper detectable effective radius of 3.5 μm and the detectable extinction coefficient range of 5 × 10−3 to 1 × 10−1 km−1. We also showed that this method is only sensitive to volcanic ash particles, but not to volcanic sulfate aerosol. This volcanic ash detection method for infrared limb measurements is a fast and reliable method and provides complementary information to existing satellite aerosol products.
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Steinwagner, J., G. Schwarz, and S. Hilgers. "Use of a Maximum Entropy Method as a Regularization Technique during the Retrieval of Trace Gas Profiles from Limb Sounding Measurements." Journal of Atmospheric and Oceanic Technology 23, no. 12 (December 1, 2006): 1657–67. http://dx.doi.org/10.1175/jtech1951.1.
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Abstract The retrieval of trace gas profiles from radiance measurements of limb sounding instruments represents an inverse problem: vertical profiles of mixing ratios have to be extracted from sequences of horizontally measured radiances recorded by a spectrometer. Typically, these retrievals are plagued by random noise and systematic errors, necessitating the use of regularization techniques during inversion calculations. In the following, the use of selected maximum entropy operators as a regularization tool is discussed and their performance with conventional optimal estimation and Tikhonov-type regularization techniques is compared. The main gain with the proposed maximum entropy operators is that no a priori knowledge is needed; a reasonable initial guess profile is fully sufficient. The approach is verified by using simulated data of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) instrument, an infrared Fourier transform spectrometer flown on the European Envisat mission.
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Davies, S., G. W. Mann, K. S. Carslaw, M. P. Chipperfield, J. J. Remedios, G. Allen, A. M. Waterfall, R. Spang, and G. C. Toon. "Testing our understanding of Arctic denitrification using MIPAS-E satellite measurements in winter 2002/3." Atmospheric Chemistry and Physics Discussions 5, no. 6 (November 1, 2005): 10997–1028. http://dx.doi.org/10.5194/acpd-5-10997-2005.
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Abstract. Observations of gas-phase HNO3 and N2O in the polar stratosphere from the Michelson Interferometer for Passive Atmospheric Sounding aboard the ENVISAT satellite (MIPAS-E) were made during the cold Arctic winter of 2002/3. Vortex temperatures were unusually low in early winter and remained favourable for polar stratospheric cloud formation and denitrification until mid-January. MIPAS-E observations provide the first dataset with sufficient coverage of the polar vortex in mid-winter which enables a reasonable estimate of the timing of onset and spatial distribution of denitrification of the Arctic lower stratosphere to be performed. We use the observations from MIPAS-E to test the evolution of denitrification in the DLAPSE (Denitrification by Lagrangian Particle Sedimentation) microphysical denitrification model coupled to the SLIMCAT chemical transport model. In addition, the predicted denitrification from a simple equilibrium nitric acid trihydrate-based scheme is also compared with MIPAS-E. Modelled denitrification is compared with in-vortex NOy and N2O observations from the balloon-borne MarkIV interferometer in mid-December. Denitrification was clearly observed by MIPAS-E in mid-December 2002 and reached 80% in the core of the vortex by early January 2003. The DLAPSE model is broadly able to capture both the timing of onset and the spatial distribution of the observed denitrification. A simple thermodynamic equilibrium scheme is able to reproduce the observed denitrification in the core of the vortex but overestimates denitrification closer to the vortex edge. This study also suggests that the onset of denitrification in simple thermodynamic schemes may be earlier than in the MIPAS-E observations.
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Moore, D. P., and J. J. Remedios. "Growth rates of stratospheric HCFC-22." Atmospheric Chemistry and Physics Discussions 7, no. 4 (July 23, 2007): 10515–41. http://dx.doi.org/10.5194/acpd-7-10515-2007.
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Abstract. The Michelson Interferometer for Passive Atmospheric Sounding onboard ENVISAT (MIPAS-E) offers the opportunity to detect and spectrally resolve many atmospheric minor constituents affecting atmospheric chemistry. In this paper, we describe an algorithm produced to retrieve HCFC–22 profiles from MIPAS-E measurements made in 2003 and present results from this scheme between 300 and 50 mb. By comparison with ATMOS (AT–3) version 3 data, we find a mean Northern Hemisphere mid-latitude (20–50° N) HCFC–22 growth rate between 1994 and 2003 of 5.4±0.7 pptv/yr in the lower stratosphere (LS) and a mean LS Southern Hemisphere growth rate (60–80°S) of 6.0±0.7 pptv/yr in the same period. We test the feasibility of using a global data set to estimate the chemical lifetime of HCFC–22 in the LS and we derive this for two regions; 20–50° N (259±38 years) and 60–80° S (288±34 years). From these data we note a global LS lifetime of 274±25 years, significantly longer than previous estimates.
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Steck, T., N. Glatthor, T. von Clarmann, H. Fischer, J. M. Flaud, B. Funke, U. Grabowski, et al. "Retrieval of global upper tropospheric and stratospheric formaldehyde (H<sub>2</sub>CO) distributions from high-resolution MIPAS-Envisat spectra." Atmospheric Chemistry and Physics 8, no. 3 (February 1, 2008): 463–70. http://dx.doi.org/10.5194/acp-8-463-2008.
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Abstract. The Fourier transform spectrometer MIPAS (Michelson Interferometer for Passive Atmospheric Sounding) on Envisat measures infrared emission of the Earth's atmosphere in a limb viewing mode. High spectral resolution measurements of MIPAS are sensitive to formaldehyde from the upper troposphere to the stratopause. Single profile retrievals of formaldehyde are dominated by a 60% noise error; however zonal mean values for 30 days of data during 8 September 2003 and 1 December 2003 reduces this error by a factor of 20 or more. The number of degrees of freedom for single profile retrieval ranges from 2 to 4.5 depending on latitude and number of cloud-free tangent altitudes. In the upper tropical troposphere zonal mean values of about 70 parts per trillion by volume (pptv) were found, which have been attributed to biomass burning emissions. In the stratosphere, formaldehyde values are determined by photochemical reactions. In the upper tropical stratosphere, formaldehyde zonal mean maximum values can reach 130 pptv. Diurnal variations in this region can be up to 50 pptv. Comparisons with other satellite instruments show generally good agreement in the region of upper troposphere and lower stratosphere as well as in the upper stratosphere.
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Cortesi, Ugo, Samuele Del Bianco, Simone Ceccherini, Marco Gai, Bianca Maria Dinelli, Elisa Castelli, Hermann Oelhaf, Wolfgang Woiwode, Michael Höpfner, and Daniel Gerber. "Synergy between middle infrared and millimeter-wave limb sounding of atmospheric temperature and minor constituents." Atmospheric Measurement Techniques 9, no. 5 (May 24, 2016): 2267–89. http://dx.doi.org/10.5194/amt-9-2267-2016.
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Abstract. Synergistic exploitation of redundant and complementary information from independent observations of the same target remains a major issue in atmospheric remote sounding and increasing attention is devoted to investigate optimized or innovative methods for the combination of two or more measured data sets. This paper focuses on the synergy between middle infrared and millimeter-wave limb sounding measurements of atmospheric composition and temperature and reports the results of a study conducted as part of the preparatory activities of the PREMIER (Process Exploration through Measurements of Infrared and millimeter-wave Emitted Radiation) mission candidate to the Core Missions of the European Space Agency (ESA) Earth Explorer 7. The activity was based on data acquired by the MIPAS-STR (Michelson Interferometer for Passive Atmospheric Sounding – STRatospheric aircraft) and MARSCHALS (Millimetre-wave Airborne Receivers for Spectroscopic CHaracterisation in Atmospheric Limb Sounding) instruments on-board the high-altitude research aircraft M-55 Geophysica during the flight of the PremierEx (PREMIER Experiment) campaign on 10 March 2010 from Kiruna, Sweden, for observation of the Arctic upper troposphere and lower stratosphere. The cloud coverage observed along the flight provided representative test cases to evaluate the synergy in three different scenarios: low clouds in the first part, no clouds in the central part and high tropospheric clouds at the end. The calculation of synergistic profiles of four atmospheric targets (i.e., O3, HNO3, H2O and temperature) was performed using a posteriori combination of individual retrieved profiles, i.e., Level 2 (L2) data rather than simultaneous inversion of observed radiances, i.e., Level 1 (L1) data. An innovative method of data fusion, based on the Measurement Space Solution (MSS) was applied along with the standard approach of inversion of MARSCHALS spectral radiances using MIPAS-STR retrieval products as a priori information (L1 + L2 method). A quantitative estimate and cross-check of the results of MSS data fusion and (L1 + L2) method was achieved based on a specific set of quantifiers including the total retrieval error, the number of degrees of freedom, the relative information distribution and the synergy factor.
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Cortesi, U., S. Del Bianco, S. Ceccherini, M. Gai, B. M. Dinelli, E. Castelli, H. Oelhaf, W. Woiwode, M. Höpfner, and D. Gerber. "Synergy between middle infrared and millimetre-wave limb sounding of atmospheric temperature and minor constituents." Atmospheric Measurement Techniques Discussions 8, no. 11 (November 10, 2015): 11673–728. http://dx.doi.org/10.5194/amtd-8-11673-2015.
Full textAbstract:
Abstract. Synergistic exploitation of redundant and complementary information from independent observations of the same target remains a major issue in atmospheric remote-sounding and increasing attention is devoted to investigate optimised or innovative methods for the combination of two or more measured data sets. This paper is focusing on the synergy between middle infrared and millimetre-wave limb sounding measurements of atmospheric composition and temperature and reports the results of a study conducted as part of the preparatory activities of the PREMIER (Process Exploration through Measurements of Infrared and millimetre wave Emitted Radiation) mission candidate to the Core Missions of ESA Earth Explorer 7. The activity was based on data acquired by the MIPAS-STR (Michelson Interferometer for Passive Atmospheric Sounding – STRatospheric aircraft) and MARSCHALS (Millimetre-wave Airborne Receivers for Spectroscopic CHaracterisation in Atmospheric Limb Sounding) instruments onboard the high altitude research aircraft M-55 Geophysica during the flight of the PremierEx (PREMIER Experiment) campaign on 10 March 2010 from Kiruna, Sweden for observation of the Arctic upper troposphere and lower stratosphere. The cloud coverage observed along the flight provided representative test cases to evaluate the synergy in three different scenarios: low clouds in the first part, no clouds in the central part and high tropospheric clouds at the end. The calculation of synergistic profiles of four atmospheric targets (i.e., O2, HNO3, H2O and temperature) was performed using a posteriori combination of individual retrieved profiles, i.e., Level 2 (L2) data rather than simultaneous inverse processing of observed radiances, i.e., Level 1 (L1) data. An innovative method of data fusion, based on the Measurement Space Solution (MSS) was applied along with the standard approach of inverse processing of MARSCHALS spectral radiances using MIPAS-STR retrieval products as a priori information (L1 + L2 method). A quantitative estimate and cross-check of the results of MSS and (L1 + L2) data fusion was achieved based on a specific set of quantifiers including the total retrieval error, the number of degrees of freedom, the relative information distribution and the synergy factor.
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Wetzel, G., T. Sugita, H. Nakajima, T. Tanaka, T. Yokota, F. Friedl-Vallon, A. Kleinert, G. Maucher, and H. Oelhaf. "Technical Note: Intercomparison of ILAS-II version 2 and 1.4 trace species with MIPAS-B measurements." Atmospheric Chemistry and Physics 8, no. 5 (February 28, 2008): 1119–26. http://dx.doi.org/10.5194/acp-8-1119-2008.
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Abstract. The Improved Limb Atmospheric Spectrometer (ILAS)-II sensor aboard the Japanese ADEOS-II satellite was launched into its sun-synchronous orbit on 14 December 2002 and performed solar occultation measurements of trace species, aerosols, temperature, and pressure in the polar stratosphere until 25 October 2003. Vertical trace gas profiles obtained with the balloon version of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS-B) provide one of the sparse data sets for validating ILAS-II version 2 and 1.4 data. The MIPAS-B limb emission spectra were collected on 20 March 2003 over Kiruna (Sweden, 68° N) at virtually the same location that has been sounded by ILAS-II about 5.5 h prior to the sampling of MIPAS-B. The intercomparison of the new ILAS-II version 2 (Northern Hemispheric sunrise) data to MIPAS-B vertical trace gas profiles shows a good to excellent agreement within the combined error limits for the species O3, N2O, CH4, H2O (above 21 km), HNO3, ClONO2, and CFC-11 (CCl3F) in the compared altitude range between 16 and 31 km such that these data appear to be very useful for scientific analysis. With regard to the previous version 1.4 ILAS-II data, significant improvements in the consistency with MIPAS-B are obvious especially for the species CH4 and H2O, but also for O3, HNO3, ClONO2, NO2, and N2O5. However, comparing gases like NO2, N2O5, and CFC-12 (CCl2F2) exhibits only poor agreement with MIPAS-B such that these species cannot be assumed to be validated at the present time.
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Höpfner, M., N. Larsen, R. Spang, B. P. Luo, J. Ma, S. H. Svendsen, S. D. Eckermann, et al. "MIPAS detects Antarctic stratospheric belt of NAT PSCs caused by mountain waves." Atmospheric Chemistry and Physics Discussions 5, no. 5 (October 26, 2005): 10723–45. http://dx.doi.org/10.5194/acpd-5-10723-2005.
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Abstract. Space borne infrared limb emission measurements by the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) reveal the formation of a belt of polar stratospheric clouds (PSCs) of nitric acid trihydrate (NAT) particles over Antarctica in mid-June 2003. By mesoscale microphysical simulations we show that this sudden onset of NAT PSCs was caused by heterogeneous nucleation on ice in the cooling phases of large-amplitude stratospheric mountain waves over the Antarctic Peninsula and the Ellsworth Mountains. MIPAS observations of PSCs before this event show no indication for the presence of NAT clouds with volume densities larger than about 0.3 μm3/cm3 and radii smaller than 3 μm, but are consistent with supercooled droplets of ternary H2SO4/HNO3/H2O solution (STS). Simulations indicate that homogeneous surface nucleation rates have to be reduced by three orders of magnitude to comply with the observations.