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@ARTICLE{Spang:22370,
      author       = {Spang, R. and Arndt, K. and Dudhia, A. and Höpfner, M. and
                      Hoffmann, L. and Hurley, J. and Grainger, R.G. and
                      Griessbach, S. and Poulsen, C. and Remedios, J.J. and Riese,
                      M. and Sembhi, H. and Siddans, R. and Waterfall, A. and
                      Zehner, C.},
      title        = {{F}ast cloud parameter retrievals of {MIPAS}/{E}nvisat},
      journal      = {Atmospheric chemistry and physics},
      volume       = {12},
      issn         = {1680-7316},
      address      = {Katlenburg-Lindau},
      publisher    = {EGU},
      reportid     = {PreJuSER-22370},
      pages        = {7135 - 7164},
      year         = {2012},
      note         = {The authors gratefully acknowledge S. P. Palm (Science
                      Systems and Applications Inc., Lanham, Maryland, USA) and
                      J.D. Spinhirne (NASA, Goddard Space Flight Centre) for
                      providing GLAS data as well as P. H. Wang (Science and
                      Technology Corporation) for preparing and providing the SAGE
                      II V6 data. The Oxford authors acknowledge support from the
                      UK National Centre for Earth Observation. R. Spang would
                      like to thank S. Rohs (Forschungszentrum Julich) for support
                      in the validation activities of SAGE II, and R. Muller
                      (Forschungszentrum Julich) for discussions on the scientific
                      objectives of the manuscript. Part of this work was
                      supported by ESA through the MIPclouds project: "Cloud
                      Information Retrieval from MIPAS Measurements",
                      AO/1-5255/06/I-OL.},
      abstract     = {The infrared limb spectra of the Michelson Interferometer
                      for Passive Atmospheric Sounding (MIPAS) on board the
                      Envisat satellite include detailed information on
                      tropospheric clouds and polar stratospheric clouds (PSC).
                      However, no consolidated cloud product is available for the
                      scientific community. Here we describe a fast prototype
                      processor for cloud parameter retrieval from MIPAS
                      (MIP-clouds). Retrieval of parameters such as cloud top
                      height, temperature, and extinction are implemented, as well
                      as retrieval of microphysical parameters, e. g. effective
                      radius and the integrated quantities over the limb path
                      (surface area density and volume density). MIPclouds
                      classifies clouds as either liquid or ice cloud in the upper
                      troposphere and polar stratospheric clouds types in the
                      stratosphere based on statistical combinations of colour
                      ratios and brightness temperature differences.Comparison of
                      limb measurements of clouds with model results or cloud
                      parameters from nadir looking instruments is often difficult
                      due to different observation geometries. We therefore
                      introduce a new concept, the limb-integrated surface area
                      density path (ADP). By means of validation and radiative
                      transfer calculations of realistic 2-D cloud fields as input
                      for a blind test retrieval (BTR), we demonstrate that ADP is
                      an extremely valuable parameter for future comparison with
                      model data of ice water content, when applying limb
                      integration (ray tracing) through the model fields. In
                      addition, ADP is used for a more objective definition of
                      detection thresholds of the applied detection methods. Based
                      on BTR, a detection threshold of ADP = 10(7) mu m(2) cm(-2)
                      and an ice water content of 10(-5) gm(-3) is estimated,
                      depending on the horizontal and vertical extent of the
                      cloud.Intensive validation of the cloud detection methods
                      shows that the limb-sounding MIPAS instrument has a
                      sensitivity in detecting stratospheric and tropospheric
                      clouds similar to that of space-and ground-based lidars,
                      with a tendency for higher cloud top heights and
                      consequently higher sensitivity for some of the MIPAS
                      detection methods. For the high cloud amount (HCA, pressure
                      levels below 440 hPa) on global scales the sensitivity of
                      MIPAS is significantly greater than that of passive nadir
                      viewers. This means that the high cloud fraction will be
                      underestimated in the ISCCP dataset compared to the amount
                      of high clouds deduced by MIPAS. Good correspondence in
                      seasonal variability and geographical distribution of cloud
                      occurrence and zonal means of cloud top height is found in a
                      detailed comparison with a climatology for subvisible cirrus
                      clouds from the Stratospheric Aerosol and Gas Experiment II
                      (SAGE II) limb sounder. Overall, validation with various
                      sensors shows the need to consider differences in
                      sensitivity, and especially the viewing geometries and
                      field-of-view size, to make the datasets comparable (e. g.
                      applying integration along the limb path through nadir cloud
                      fields). The simulation of the limb path integration will be
                      an important issue for comparisons with cloud-resolving
                      global circulation or chemical transport models.},
      keywords     = {J (WoSType)},
      cin          = {IEK-7 / JSC},
      ddc          = {550},
      cid          = {I:(DE-Juel1)IEK-7-20101013 / I:(DE-Juel1)JSC-20090406},
      pnm          = {Atmosphäre und Klima (FUEK491) / 411 - Computational
                      Science and Mathematical Methods (POF2-411)},
      pid          = {G:(DE-Juel1)FUEK491 / G:(DE-HGF)POF2-411},
      shelfmark    = {Meteorology $\&$ Atmospheric Sciences},
      typ          = {PUB:(DE-HGF)16},
      UT           = {WOS:000308287000025},
      doi          = {10.5194/acp-12-7135-2012},
      url          = {https://juser.fz-juelich.de/record/22370},
}