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@ARTICLE{Spang:811918,
author = {Spang, Reinhold and Hoffmann, Lars and Höpfner, Michael
and Griessbach, Sabine and Müller, Rolf and Pitts, Michael
C. and Orr, Andrew M. W. and Riese, Martin},
title = {{A} multi-wavelength classification method for polar
stratospheric cloud types using infrared limb spectra},
journal = {Atmospheric measurement techniques},
volume = {9},
number = {8},
issn = {1867-8548},
address = {Katlenburg-Lindau},
publisher = {Copernicus},
reportid = {FZJ-2016-04232},
pages = {3619 - 3639},
year = {2016},
abstract = {The Michelson Interferometer for Passive Atmospheric
Sounding (MIPAS) instrument on board the ESA Envisat
satellite operated from July 2002 until April 2012. The
infrared limb emission measurements represent a unique
dataset of daytime and night-time observations of polar
stratospheric clouds (PSCs) up to both poles. Cloud
detection sensitivity is comparable to space-borne lidars,
and it is possible to classify different cloud types from
the spectral measurements in different atmospheric windows
regions.Here we present a new infrared PSC classification
scheme based on the combination of a well-established
two-colour ratio method and multiple 2-D brightness
temperature difference probability density functions. The
method is a simple probabilistic classifier based on Bayes'
theorem with a strong independence assumption. The method
has been tested in conjunction with a database of radiative
transfer model calculations of realistic PSC particle size
distributions, geometries, and composition. The Bayesian
classifier distinguishes between solid particles of ice and
nitric acid trihydrate (NAT), as well as liquid droplets of
super-cooled ternary solution (STS).The classification
results are compared to coincident measurements from the
space-borne lidar Cloud-Aerosol Lidar with Orthogonal
Polarization (CALIOP) instrument over the temporal overlap
of both satellite missions (June 2006–March 2012). Both
datasets show a good agreement for the specific PSC classes,
although the viewing geometries and the vertical and
horizontal resolution are quite different. Discrepancies are
observed between the CALIOP and the MIPAS ice class. The
Bayesian classifier for MIPAS identifies substantially more
ice clouds in the Southern Hemisphere polar vortex than
CALIOP. This disagreement is attributed in part to the
difference in the sensitivity on mixed-type clouds. Ice
seems to dominate the spectral behaviour in the limb
infrared spectra and may cause an overestimation in ice
occurrence compared to the real fraction of ice within the
PSC area in the polar vortex.The entire MIPAS measurement
period was processed with the new classification approach.
Examples like the detection of the Antarctic NAT belt during
early winter, and its possible link to mountain wave events
over the Antarctic Peninsula, which are observed by the
Atmospheric Infrared Sounder (AIRS) instrument, highlight
the importance of a climatology of 9 Southern Hemisphere and
10 Northern Hemisphere winters in total. The new dataset is
valuable both for detailed process studies, and for
comparisons with and improvements of the PSC
parameterizations used in chemistry transport and climate
models.},
cin = {JSC / IEK-7},
ddc = {550},
cid = {I:(DE-Juel1)JSC-20090406 / I:(DE-Juel1)IEK-7-20101013},
pnm = {244 - Composition and dynamics of the upper troposphere and
middle atmosphere (POF3-244) / 511 - Computational Science
and Mathematical Methods (POF3-511)},
pid = {G:(DE-HGF)POF3-244 / G:(DE-HGF)POF3-511},
typ = {PUB:(DE-HGF)16},
UT = {WOS:000383146000001},
doi = {10.5194/amt-9-3619-2016},
url = {https://juser.fz-juelich.de/record/811918},
}