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A climatology of polar stratospheric cloud composition between 2002 and 2012 based on MIPAS/Envisat observations
Ist Teil von
Atmospheric chemistry and physics, 2018-04, Vol.18 (7), p.5089-5113
Ort / Verlag
Katlenburg-Lindau: Copernicus GmbH
Erscheinungsjahr
2018
Link zum Volltext
Quelle
EZB-FREE-00999 freely available EZB journals
Beschreibungen/Notizen
The Michelson Interferometer for Passive Atmospheric
Sounding (MIPAS) instrument aboard the European Space Agency (ESA) Envisat satellite operated from
July 2002 to April 2012. The infrared limb emission measurements provide
a unique dataset of day and night observations of polar stratospheric clouds
(PSCs) up to both poles. A recent classification method for PSC types in infrared (IR)
limb spectra using spectral measurements in different atmospheric window
regions has been applied to the complete mission period of MIPAS. The method
uses a simple probabilistic classifier based on Bayes' theorem with a strong
independence assumption on a combination of a well-established two-colour
ratio method and multiple 2-D probability density functions of brightness
temperature differences. The Bayesian classifier distinguishes between solid
particles of ice, nitric acid trihydrate (NAT), and liquid droplets of
supercooled ternary solution (STS), as well as mixed types. A climatology of MIPAS PSC occurrence and specific PSC classes has been
compiled. Comparisons with results from the classification scheme of the
spaceborne lidar Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP)
on the Cloud-Aerosol-Lidar and Infrared Pathfinder Satellite Observations
(CALIPSO) satellite show excellent correspondence in the spatial and
temporal evolution for the area of PSC coverage (APSC) even for each
PSC class. Probability density functions of the PSC temperature, retrieved
for each class with respect to equilibrium temperature of ice and based on
coincident temperatures from meteorological reanalyses, are in accordance
with the microphysical knowledge of the formation processes with respect to
temperature for all three PSC types. This paper represents unprecedented pole-covering day- and nighttime
climatology of the PSC distributions and their composition of different
particle types. The dataset allows analyses on the temporal and spatial
development of the PSC formation process over multiple winters. At first
view, a more general comparison of APSC and AICE retrieved from
the observations and from the existence temperature for NAT and ice
particles based on the European Centre for Medium-Range Weather Forecasts (ECMWF) reanalysis temperature data shows the high potential
of the climatology for the validation and improvement of PSC schemes in
chemical transport and chemistry–climate models.