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  • 1.
    Baron, P.
    et al.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Urban, J.
    Chalmers University of Technology.
    Sagawa, H.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Möller, J.
    Chalmers University of Technology.
    Mendrok, Jana
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Dupuy, E.
    Sato, T.O,
    Ochiai, Satoshi
    National Institute of Information and Communication Technology, Tokyo.
    Suzuk, K.
    Manabe, T.
    Osaka Prefecture University, Naka, Sakai.
    Nishibori, T.
    Japan Aerospace Exploration Agency (JAXA), Tsukuba.
    Kikuchi, K.
    Sato, R.
    Takayanagi, M.
    Murayama, Y.
    Shiotani, M.
    Research Institute for Sustainable Humanosphere, Kyoto University.
    Kasai, Y.
    The Level 2 research product algorithms for the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES)2011In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 4, p. 2105-2124Article in journal (Refereed)
    Abstract [en]

    This paper describes the algorithms of the level-2 research (L2r) processing chain developed for the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES). The chain has been developed in parallel to the operational chain for conducting researches on calibration and retrieval algorithms. L2r chain products are available to the scientific community. The objective of version 2 is the retrieval of the vertical distribution of trace gases in the altitude range of 18–90 km. A theoretical error analysis is conducted to estimate the retrieval feasibility of key parameters of the processing: line-of-sight elevation tangent altitudes (or angles), temperature and ozone profiles. While pointing information is often retrieved from molecular oxygen lines, there is no oxygen line in the SMILES spectra, so the strong ozone line at 625.371 GHz has been chosen. The pointing parameters and the ozone profiles are retrieved from the line wings which are measured with high signal to noise ratio, whereas the temperature profile is retrieved from the optically thick line center. The main systematic component of the retrieval error was found to be the neglect of the non-linearity of the radiometric gain in the calibration procedure. This causes a temperature retrieval error of 5–10 K. Because of these large temperature errors, it is not possible to construct a reliable hydrostatic pressure profile. However, as a consequence of the retrieval of pointing parameters, pressure induced errors are significantly reduced if the retrieved trace gas profiles are represented on pressure levels instead of geometric altitude levels. Further, various setups of trace gas retrievals have been tested. The error analysis for the retrieved HOCl profile demonstrates that best results for inverting weak lines can be obtained by using narrow spectral windows.

  • 2.
    Buehler, Stefan
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Defer, E.
    CNRS, Laboratoire d'Etudes du Rayonnement et de la Matière en Astrophysique, Observatoire de Paris.
    Evans, F.
    Department of Atmospheric and Oceanic Sciences, University of Colorado, Boulder.
    Eliasson, Salomon
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Mendrok, Jana
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Erikssson, P.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Lee, C.
    Met Office Hadley Centre, Exeter.
    Jimenez, C.
    CNRS, Laboratoire d'Etudes du Rayonnement et de la Matière en Astrophysique, Observatoire de Paris.
    Prigent, C.
    CNRS, Laboratoire d'Etudes du Rayonnement et de la Matière en Astrophysique, Observatoire de Paris.
    Crewell, S.
    Institute for Geophysics and Meteorology, University of Cologne.
    kasai, Y.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Bennartz, R.
    Atmospheric and Oceanic Sciences, University of Wisconsin.
    Gasiewski, A.J.
    NOAA-CU Center for Environmental Technology (CET), Department of Electrical and Computer Engineering, University of Colorado at Boulder.
    Observing ice clouds in the submillimeter spectral range: the CloudIce mission proposal for ESA's Earth Explorer 82012In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 5, no 7, p. 1529-1549Article in journal (Refereed)
    Abstract [en]

    Passive submillimeter-wave sensors are a way to obtain urgently needed global data on ice clouds, particularly on the so far poorly characterized 'essential climate variable' ice water path (IWP) and on ice particle size. CloudIce was a mission proposal to the European Space Agency ESA in response to the call for Earth Explorer 8 (EE8), which ran in 2009/2010. It proposed a passive submillimeter-wave sensor with channels ranging from 183 GHz to 664 GHz. The article describes the CloudIce mission proposal, with particular emphasis on describing the algorithms for the data-analysis of submillimeter-wave cloud ice data (retrieval algorithms) and demonstrating their maturity. It is shown that we have a robust understanding of the radiative properties of cloud ice in the millimeter/submillimeter spectral range, and that we have a proven toolbox of retrieval algorithms to work with these data. Although the mission was not selected for EE8, the concept will be useful as a reference for other future mission proposals.

  • 3.
    Chauhan, Swarup
    et al.
    Forschungszentrum Karlsruhe.
    Höpfner, M.
    Stiller, G.P.
    Clarmann, T. von
    Funke, B.
    Glatthor, N.
    Grabowski, U.
    Linden, A.
    Kellmann, S.
    Milz, Mathias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Steck, T.
    Fischer, H.
    Froidevaux, L.
    Lambert, A.
    Santee, M. L.
    Schwartz, M.
    Read, W.G.
    Livesey, N.
    MIPAS reduced spectral resolution UTLS-1 mode measurements of temperature, O3, HNO3, N2O, H2O and relative humidity over ice: retrievals and comparison to MLS2009In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, no 2, p. 337-353Article in journal (Refereed)
    Abstract [en]

    During several periods since 2005 the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS) on Envisat has performed observations dedicated to the region of the upper troposphere/lower stratosphere (UTLS). For the duration of November/December 2005 global distributions of temperature and several trace gases from MIPAS UTLS-1 mode measurements have been retrieved using the IMK/IAA (Institut für Meteorologie und Klimaforschung/Instituto de Astrofísica de Andalucía) scientific processor. In the UTLS region a vertical resolution of 3 km for temperaure, 3 to 4 km for H2O, 2.5 to 3 km for O3, 3.5 km for HNO3 and 3.5 to 2.5 km for N2O has been achieved. The retrieved temperature, H2O, O3, HNO3, N2O, and relative humidity over ice are intercompared with the Microwave Limb Sounder (MLS/Aura) v2.2 data in the pressure range 316 to 0.68 hPa, 316 to 0.68 hPa, 215 to 0.68 hPa, 215 to 3.16 hPa, 100 to 1 hPa and 316 to 10 hPa, respectively. In general, MIPAS and MLS temperatures are biased within ±4 K over the whole pressure and latitude range. Systematic, latitude-independent differences of −2 to −4 K (MIPAS-MLS) at 121 hPa are explained by previously observed biases in the MLS v2.2 temperature retrievals. Temperature differences of −4 K up to 12 K above 10.0 hPa are present both in MIPAS and MLS with respect to ECMWF (European Centre for Medium-Range Weather Forecasts) and are likely due to deficiencies of the ECMWF analysis data. MIPAS and MLS stratospheric volume mixing ratios (vmr) of H2O are biased within ±1 ppmv, with indication of oscillations between 146 and 26 hPa in the MLS dataset. Tropical upper tropospheric values of relative humidity over ice measured by the two instruments differ by ±20% in the pressure range ~146 to 68 hPa. These differences are mainly caused by the MLS temperature biases. Ozone mixing ratios agree within 0.5 ppmv (10 to 20%) between 68 and 14 hPa. At pressures smaller than 10 hPa, MIPAS O3 vmr are higher than MLS by an average of 0.5 ppmv (10%). General agreement between MIPAS and MLS HNO3 is within the range of −1.0 (−10%) to 1.0 ppbv (20%). MIPAS HNO3 is 1.0 ppbv (10%) higher compared to MLS between 46 hPa and 10 hPa over the Northern Hemisphere. Over the tropics at 31.6 hPa MLS shows a low bias of more than 1 ppbv (>50%). In general, MIPAS and MLS N2O vmr agree within 20 to 40 ppbv (20 to 40%). Differences in the range between 100 to 21 hPa are attributed to a known 20% positive bias in MIPAS N2O data.

  • 4.
    Eriksson, Patrick E J
    et al.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Jamali, Maryam
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Mendrok, Jana
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Buehler, Stefan
    Meteorological Institute, Center for Earth System Research and Sustainability, University of Hamburg.
    On the microwave optical properties of randomly oriented ice hydrometeors2015In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 8, no 5, p. 1913-1933Article in journal (Refereed)
    Abstract [en]

    Microwave remote sensing is important for observing the mass of ice hydrometeors. One of the main error sources of microwave ice mass retrievals is that approximations around the shape of the particles are unavoidable. One common approach to represent particles of irregular shape is the soft particle approximation (SPA). We show that it is possible to define a SPA that mimics mean optical particles of available reference data over narrow frequency ranges, considering a single observation technique at the time, but that SPA does not work in a broader context. Most critically, the required air fraction varies with frequency and application, as well as with particle size. In addition, the air fraction matching established density parameterisations results in far too soft particles, at least for frequencies above 90 GHz. That is, alternatives to SPA must be found. One alternative was recently presented by Geer and Baordo (2014). They used a subset of the same reference data and simply selected as "shape model" the particle type giving the best overall agreement with observations. We present a way to perform the same selection of a representative particle shape but without involving assumptions on particle size distribution and actual ice mass contents. Only an assumption on the occurrence frequency of different particle shapes is still required. Our analysis leads to the same selection of representative shape as found by Geer and Baordo (2014). In addition, we show that the selected particle shape has the desired properties at higher frequencies as well as for radar applications. Finally, we demonstrate that in this context the assumption on particle shape is likely less critical when using mass equivalent diameter to characterise particle size compared to using maximum dimension, but a better understanding of the variability of size distributions is required to fully characterise the advantage. Further advancements on these subjects are presently difficult to achieve due to a lack of reference data. One main problem is that most available databases of precalculated optical properties assume completely random particle orientation, while for certain conditions a horizontal alignment is expected. In addition, the only database covering frequencies above 340 GHz has a poor representation of absorption as it is based on outdated refractive index data as well as only covering particles having a maximum dimension below 2 mm and a single temperature

  • 5.
    Eriksson, Patrick
    et al.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Rydberg, B.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    On cloud ice induced absorption and polarisation effects in microwave limb sounding2011In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 4, no 6, p. 1305-1318Article in journal (Refereed)
    Abstract [en]

    Microwave limb sounding in the presence of ice clouds was studied by detailed simulations, where clouds and other atmospheric variables varied in three dimensions and the full polarisation state was considered. Scattering particles were assumed to be horizontally aligned oblate spheroids with a size distribution parameterized in terms of temperature and ice water content. A general finding was that particle absorption is significant for limb sounding, which is in contrast to the down-looking case, where it is usually insignificant. Another general finding was that single scattering can be assumed for cloud optical paths below about 0.1, which is thus an important threshold with respect to the complexity and accuracy of retrieval algorithms. The representation of particle sizes during the retrieval is also discussed. Concerning polarisation, specific findings were as follows: Firstly, no significant degree of circular polarisation was found for the considered particle type. Secondly, for the +/- 45 degrees polarisation components, differences of up to 4 K in brightness temperature were found, but differences were much smaller when single scattering conditions applied. Thirdly, the vertically polarised component has the smallest cloud extinction. An important goal of the study was to derive recommendations for future limb sounding instruments, particularly concerning their polarisation setup. If ice water content is among the retrieval targets (and not just trace gas mixing ratios), then the simulations show that it should be best to observe any of the +/- 45 degrees and circularly polarised components. These pairs of orthogonal components also make it easier to combine information measured from different positions and with different polarisations

  • 6. Holl, Gerrit
    et al.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Rydberg, B.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Jiménez, C.
    Laboratoire d'Etude du Rayonnement et de la Matière en Astrophysique, Centre National de la Recherche Scientifique, Observatoire de Paris.
    Collocating satellite-based radar and radiometer measurements: methodology and usage examples2010In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 3, no 3, p. 693-708Article in journal (Refereed)
    Abstract [en]

    Collocations between two satellite sensors are occasions where both sensors observe the same place at roughly the same time. We study collocations between the Microwave Humidity Sounder (MHS) on-board NOAA-18 and the Cloud Profiling Radar (CPR) on-board CloudSat. First, a simple method is presented to obtain those collocations and this method is compared with a more complicated approach found in literature. We present the statistical properties of the collocations, with particular attention to the effects of the differences in footprint size. For 2007, we find approximately two and a half million MHS measurements with CPR pixels close to their centrepoints. Most of those collocations contain at least ten CloudSat pixels and image relatively homogeneous scenes. In the second part, we present three possible applications for the collocations. Firstly, we use the collocations to validate an operational Ice Water Path (IWP) product from MHS measurements, produced by the National Environment Satellite, Data and Information System (NESDIS) in the Microwave Surface and Precipitation Products System (MSPPS). IWP values from the CloudSat CPR are found to be significantly larger than those from the MSPPS. Secondly, we compare the relation between IWP and MHS channel 5 (190.311 GHz) brightness temperature for two datasets: the collocated dataset, and an artificial dataset. We find a larger variability in the collocated dataset. Finally, we use the collocations to train an Artificial Neural Network and describe how we can use it to develop a new MHS-based IWP product. We also study the effect of adding measurements from the High Resolution Infrared Radiation Sounder (HIRS), channels 8 (11.11 mu m) and 11 (8.33 mu m). This shows a small improvement in the retrieval quality. The collocations described in the article are available for public use

  • 7.
    Kasai, Y.
    et al.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Sagawa, H.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Kreyling, D.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Dupuy, E.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Baron, P.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Mendrok, Jana
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Suzuki, K.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Sato, T.O.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Nishibori, T.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Mizobuchi, S.
    Japan Aerospace Exploration Agency (JAXA), Tsukuba.
    Kikuchi, K.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Manabe, T.
    Osaka Prefecture University, Naka, Sakai.
    Ozeki, H.
    Toho University, Funabashi, Chiba.
    Sugita, T.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Fujiwara, M.
    Toho University, Funabashi, Chiba.
    Irimajiri, Y.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Walker, K.A.
    University of Toronto.
    Bernath, P.F.
    Old Dominion University, Norfolk, Virginia.
    Boone, C.
    University of Waterloo.
    Stiller, G.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Clarmann, T. von
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Orphal, J.
    Forschungszentrum Karlsruhe, Institut für Meteorologie und Klimaforschung Karlsruhe.
    Urban, J.
    Chalmers University of Technology.
    Murtagh, D.
    Chalmers University of Technology.
    Llewellyn, E.J.
    Institute of Space and Atmospheric Studies, University of Saskatchewan.
    Yasui, M.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Validation of stratospheric and mesospheric ozone observed by SMILES from International Space Station2013In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 6, no 9, p. 2311-2338Article in journal (Refereed)
    Abstract [en]

    We observed ozone (O3) in the vertical region between 250 and 0.0005 hPa (~ 12–96 km) using the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) on the Japanese Experiment Module (JEM) of the International Space Station (ISS) between 12 October 2009 and 21 April 2010. The new 4 K superconducting heterodyne receiver technology of SMILES allowed us to obtain a one order of magnitude better signal-to-noise ratio for the O3 line observation compared to past spaceborne microwave instruments. The non-sun-synchronous orbit of the ISS allowed us to observe O3 at various local times. We assessed the quality of the vertical profiles of O3 in the 100–0.001 hPa (~ 16–90 km) region for the SMILES NICT Level 2 product version 2.1.5. The evaluation is based on four components: error analysis; internal comparisons of observations targeting three different instrumental setups for the same O3 625.371 GHz transition; internal comparisons of two different retrieval algorithms; and external comparisons for various local times with ozonesonde, satellite and balloon observations (ENVISAT/MIPAS, SCISAT/ACE-FTS, Odin/OSIRIS, Odin/SMR, Aura/MLS, TELIS). SMILES O3 data have an estimated absolute accuracy of better than 0.3 ppmv (3%) with a vertical resolution of 3–4 km over the 60 to 8 hPa range. The random error for a single measurement is better than the estimated systematic error, being less than 1, 2, and 7%, in the 40–1, 80–0.1, and 100–0.004 hPa pressure regions, respectively. SMILES O3 abundance was 10–20% lower than all other satellite measurements at 8–0.1 hPa due to an error arising from uncertainties of the tangent point information and the gain calibration for the intensity of the spectrum. SMILES O3 from observation frequency Band-B had better accuracy than that from Band-A. A two month period is required to accumulate measurements covering 24 h in local time of O3 profile. However such a dataset can also contain variation due to dynamical, seasonal, and latitudinal effects

  • 8.
    Larsson, Richard
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Milz, Mathias
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Rayer, Peter
    UK Met Office, Exeter.
    Saunders, Roger
    UK Met Office, Exeter.
    Bell, William
    UK Met Office, Exeter.
    Booton, Anna
    UK Met Office, Exeter.
    Buehler, Stephan A.
    Meteorological Institute, University of Hamburg, Hamburg.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Earth and Space Sciences.
    John, Viju E.
    EUMETSAT, Darmstadt.
    Modeling the Zeeman effect in high altitude SSMIS channels for numerical weather prediction profiles: Comparing a fast model and a line-by-line model2016In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 9, no 2, p. 841-857Article in journal (Refereed)
    Abstract [en]

    We present a comparison of a reference and a fast radiative transfer model using numerical weather prediction profiles for the Zeeman-affected high altitude Special Sensor Microwave Imager/Sounder channels 19–22. We find that the models agree well for channels 21 and 22 compared to the channels' system noise temperatures (1.9 and 1.3 K, respectively) and the expected profile errors at the affected altitudes (estimated to be around 5 K). For channel 22 there is a 0.5 K average difference between the models, with a standard deviation of 0.24 K for the full set of atmospheric profiles. Same channel, there is 1.2 K in average between the fast model and the sensor measurement, with 1.4 K standard deviation. For channel 21 there is a 0.9 K average difference between the models, with a standard deviation of 0.56 K. Same channel, there is 1.3 K in average between the fast model and the sensor measurement, with 2.4 K standard deviation. We consider the relatively small model differences as a validation of the fast Zeeman effect scheme for these channels. Both channels 19 and 20 have smaller average differences between the models (at below 0.2 K) and smaller standard deviations (at below 0.4 K) when both models use a two-dimensional magnetic field profile. However, when the reference model is switched to using a full three-dimensional magnetic field profile, the standard deviation to the fast model is increased to almost 2 K due to viewing geometry dependencies causing up to ± 7 K differences near the equator. The average differences between the two models remain small despite changing magnetic field configurations. We are unable to compare channels 19 and 20 to sensor measurements due to limited altitude range of the numerical weather prediction profiles. We recommended that numerical weather prediction software using the fast model takes the available fast Zeeman scheme into account for data assimilation of the affected sensor channels to better constrain the upper atmospheric temperatures.

  • 9.
    Milz, Mathias
    et al.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Clarmann, T. von
    Forschungszentrum Karlsruhe.
    Bernath, P.
    University of York, Department of Chemistry.
    Boone, C.
    University of Waterloo, Deptment of Chemistry, Waterloo.
    Buehler, Stefan
    Chauhan, S.
    Forschungszentrum Karlsruhe.
    Deuber, B.
    University of Bern, Institute of Applied Physics, Atmospheric Research Group.
    Feist, D.G.
    Max-Planck-Institut für Biogeochemie, Jena.
    Funke, B.
    Instituto de Astrofísica de Andalucía CSIC, Granada.
    Glatthor, N.
    Forschungszentrum Karlsruhe.
    Grabowski, U.
    Forschungszentrum Karlsruhe.
    Griesfeller, A.
    CNRS, UVSQ, LATMOS, Verrieres Le Buisson.
    Haefele, A.
    University of Bern, Institute of Applied Physics, Atmospheric Research Group.
    Höpfner, M.
    Forschungszentrum Karlsruhe.
    Kämpfer, N.
    University of Bern, Institute of Applied Physics, Atmospheric Research Group.
    Kellmann, S.
    Forschungszentrum Karlsruhe.
    Linden, A.
    Forschungszentrum Karlsruhe.
    Müller, S.
    University of Bern, Institute of Applied Physics, Atmospheric Research Group.
    Nakajima, H.
    National Institute for Environmental Studies, Tsukuba.
    Oelhaf, H.
    Forschungszentrum Karlsruhe.
    Remsberg, E.
    NASA, Langley Research Centre, Scientific Directorate.
    Rohs, S.
    Forschungszentrum Julich.
    Russell, J.M.
    Hampton University, Department of Physics.
    Schiller, C.
    Forschungszentrum Julich.
    Sugita, T.
    National Institute for Environmental Studies, Tsukuba.
    Zhang, G.
    Forschungszentrum Karlsruhe.
    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 Envisat2009In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, no 2, p. 379-399Article in journal (Refereed)
    Abstract [en]

    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 indicationof 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. Theresults of chi2-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 chi2 values found are in the expected range or even below. This suggests that there is no evidence of systematically underestimated MIPAS random errors.

  • 10.
    Navas-Guzmán, Francisco
    et al.
    Institute of Applied Physics, University of Bern.
    Kämpfer, Nklaus
    Institute of Applied Physics, University of Bern.
    Murk, Axel
    Institute of Applied Physics, University of Bern.
    Larsson, Richard
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Buehler, Stefan
    Meteorological Institute, Center for Earth System Research and Sustainability, University of Hamburg.
    Eriksson, Patrik
    Chalmers University of Technology, Chalmers University of Technology, Department of Earth and Space Sciences.
    Zeeman effect in atmospheric O2 measured by ground-based microwave radiometry2015In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 8, no 4, p. 1863-1874Article in journal (Refereed)
    Abstract [en]

    In this work we study the Zeeman effect on stratospheric O2 using ground-based microwave radiometer measurements. The interaction of the Earth magnetic field with the oxygen dipole leads to a splitting of O2 energy states, which polarizes the emission spectra. A special campaign was carried out in order to measure this effect in the oxygen emission line centered at 53.07 GHz. Both a fixed and a rotating mirror were incorporated into the TEMPERA (TEMPERature RAdiometer) in order to be able to measure under different observational angles. This new configuration allowed us to change the angle between the observational path and the Earth magnetic field direction. Moreover, a high-resolution spectrometer (1 kHz) was used in order to measure for the first time the polarization state of the radiation due to the Zeeman effect in the main isotopologue of oxygen from ground-based microwave measurements. The measured spectra showed a clear polarized signature when the observational angles were changed, evidencing the Zeeman effect in the oxygen molecule. In addition, simulations carried out with the Atmospheric Radiative Transfer Simulator (ARTS) allowed us to verify the microwave measurements showing a very good agreement between model and measurements. The results suggest some interesting new aspects for research of the upper atmosphere

  • 11.
    Rydberg, Bengt
    et al.
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Murtagh, Donal
    Chalmers University of Technology, Department of Radio and Space Science, Gothenburg.
    Non-Gaussian Bayesian retrieval of tropical upper tropospheric cloud ice and water vapour from Odin-SMR measurements2009In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 2, no 2, p. 621-637Article in journal (Refereed)
    Abstract [en]

    Improved Odin-SMR retrievals of upper tropospheric water are presented. The new retrieval algorithm retrieves humidity and cloud ice mass simultaneously and takes into account of cloud inhomogeneities. Both these aspects are introduced for microwave limb sounding inversions for the first time. A Bayesian methodology is applied allowing for a formally correct treatment of non-unique retrieval problems involving non-Gaussian statistics. Cloud structure information from CloudSat is incorporated into the retrieval algorithm. This removes a major limitation of earlier inversion methods where uniform cloud layers were assumed and caused a systematic retrieval error. The core part ofthe retrieval technique is the generation of a database that must closely represent real conditions. Good agreement with Odin-SMR observations indicates that this requirement is met. The retrieval precision is determined to be about 5–17% RHi and 65% for humidity and cloud ice mass, respectively.For both quantities, the vertical resolution is about 5 km and the best retrieval performance is found between 11 and 15 km. New data show a significantly improved agreement with CloudSat cloud ice mass retrievals, at the same time consistency with the Aura MLS humidity results is maintained. The basics of the approach presented can be applied for all passive cloud observations and should be of broad interest. The results can also be taken as a demonstration of the potential of down-looking sub-mm radiometry for global measurements of cloud ice properties.

  • 12.
    Rüfenacht, R.
    et al.
    Institute of Applied Physics, University of Bern.
    Murk, A.
    Institute of Applied Physics, University of Bern.
    Kämpfer, N.
    Institute of Applied Physics, University of Bern.
    Eriksson, P.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Buehler, S. A.
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology. Division of Space Technology, SRT, Luleä University of Technology.
    Middle-atmospheric zonal and meridional wind profiles from polar, tropical and midlatitudes with the ground-based microwave Doppler wind radiometer WIRA2014In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 7, p. 4491-4505Article in journal (Refereed)
    Abstract [en]

    WIRA is a ground-based microwave Doppler spectroradiometer specifically designed for the measurement of profiles of horizontal wind in the upper stratosphere and lower mesosphere region where no other continuously running measurement technique exists. A proof of principle has been delivered in a previous publication. A technical upgrade including a new high-frequency amplifier and sideband filter has improved the signal to noise ratio by a factor of 2.4. Since this upgrade the full horizontal wind field comprising zonal and meridional wind profiles is continuously measured. A completely new retrieval based on optimal estimation has been set up. Its characteristics are detailed in the present paper. Since the start of the routine operation of the first prototype in September 2010, WIRA has been measuring at four different locations at polar, mid- and tropical latitudes (67°22′ N/26°38′ E, 46°57′ N/7°26′ E, 43°56′ N/5°43′ E and 21°04′ S/55°23′ E) for time periods between 5.5 and 11 months. The data presented in this paper are daily average wind profiles with typical uncertainties and resolutions of 10 to 20 m s−1 and 10 to 16 km, respectively. A comparison between the data series from WIRA and European Centre for Medium-Range Weather Forecasts (ECMWF) model data revealed agreement within 10% in the stratospheric zonal wind. The meridional wind profiles agree within their error bars over the entire sensitive altitude range of WIRA. However, significant differences in the mesospheric zonal wind speed of up to 50% have been found.

  • 13.
    Rüfenacht, R.
    et al.
    Institute of Applied Physics, University of Bern.
    Murk, A.
    Institute of Applied Physics, University of Bern.
    Kämpfer, N.
    Institute of Applied Physics, University of Bern.
    Eriksson, P.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Buehler, Stefan
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Middle-atmospheric zonal and meridional wind profiles from polar, tropical and midlatitudes with the ground-based microwave Doppler wind radiometer WIRA2014In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 7, p. 7717-7752Article in journal (Refereed)
    Abstract [en]

    WIRA is a ground-based microwave Doppler spectro radiometer specifically designed for the measurement of profiles of horizontal wind in the upper stratosphere and lower mesosphere region where no other continuously running measurement technique exists. A proof of principle has been delivered in a previous publication. Since a technical upgrade which improved the signal to noise ratio by a factor of 2.4 the full horizontal wind field comprising zonal and meridional wind profiles is continuously measured. A completely new retrieval based on optimal estimation has been set up. Its characteristics are detailed in the present paper.Since the start of the routine operation of the first prototype in September 2010, WIRA has been measuring at four different locations at polar, mid and tropical latitudes for time periods between 5.5 and 11 months. A comparison between the data series from WIRA and ECMWF model data revealed agreement within 10% in the stratospheric zonal wind. The meridional wind profiles agree within their error bars over the entire sensitive altitude range of WIRA. However, significant differences in the mesospheric zonal wind speed of up to 40% have been found.

  • 14.
    Sato, T.O.
    et al.
    Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama.
    Sagawa, H.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Kreyling, D.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Manabe, T.
    Osaka Prefecture University, Naka, Sakai.
    Ochiai, S.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Kikuchi, K.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Baron, P.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Mendrok, Jana
    Luleå University of Technology, Department of Computer Science, Electrical and Space Engineering, Space Technology.
    Urban, J.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Murtagh, D.
    Chalmers University of Technology, Department of Earth and Space Sciences.
    Yasui, M.
    National Institute of Information and Communications Technology, 4-2-1 Nukui-kitamachi, Koganei.
    Kasai, Y.
    Tokyo Institute of Technology, 4259 Nagatsuta-cho, Midori-ku, Yokohama.
    Strato-mesospheric ClO observations by SMILES: error analysis and diurnal variation2012In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 5, no 11, p. 2809-2825Article in journal (Refereed)
    Abstract [en]

    Chlorine monoxide (ClO) is the key species for anthropogenic ozone losses in the middle atmosphere. We observed ClO diurnal variations using the Superconducting Submillimeter-Wave Limb-Emission Sounder (SMILES) on the International Space Station, which has a non-sun-synchronous orbit. This includes the first global observations of the ClO diurnal variation from the stratosphere up to the mesosphere. The observation of mesospheric ClO was possible due to 10–20 times better signal-to-noise (S/N) ratio of the spectra than those of past or ongoing microwave/submillimeter-wave limb-emission sounders. We performed a quantitative error analysis for the strato- and mesospheric ClO from the Level-2 research (L2r) product version 2.1.5 taking into account all possible contributions of errors, i.e. errors due to spectrum noise, smoothing, and uncertainties in radiative transfer model and instrument functions. The SMILES L2r v2.1.5 ClO data are useful over the range from 0.01 and 100 hPa with a total error estimate of 10–30 pptv (about 10%) with averaging 100 profiles. The SMILES ClO vertical resolution is 3–5 km and 5–8 km for the stratosphere and mesosphere, respectively. The SMILES observations reproduced the diurnal variation of stratospheric ClO, with peak values at midday, observed previously by the Microwave Limb Sounder on the Upper Atmosphere Research Satellite (UARS/MLS). Mesospheric ClO demonstrated an opposite diurnal behavior, with nighttime values being larger than daytime values. A ClO enhancement of about 100 pptv was observed at 0.02 to 0.01 hPa (about 70–80 km) for 50° N–65° N from January–February 2010. The performance of SMILES ClO observations opens up new opportunities to investigate ClO up to the mesopause.

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