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@ARTICLE{BartolomGarca:1022543,
author = {Bartolomé García, Irene and Sourdeval, Odran and Spang,
Reinhold and Krämer, Martina},
title = {{T}echnical note: {B}imodal parameterizations of in situ
ice cloud particle size distributions},
journal = {Atmospheric chemistry and physics},
volume = {24},
number = {3},
issn = {1680-7316},
address = {Katlenburg-Lindau},
publisher = {EGU},
reportid = {FZJ-2024-01520},
pages = {1699 - 1716},
year = {2024},
abstract = {The cloud particle size distribution (PSD) is a key
parameter for the retrieval of microphysical and optical
properties from remote-sensing instruments, which in turn
are necessary for determining the radiative effect of
clouds. Current representations of PSDs for ice clouds rely
on parameterizations that were largely based on aircraft in
situ measurements where the distribution of small ice
crystals were uncertain. This makes current
parameterizations deficient to simulate remote-sensing
observations sensitive to small ice, such as from lidar and
thermal infrared instruments. In this study we fit the in
situ PSDs of ice crystals from the JULIA (JÜLich In situ
Aircraft data set) database, which consists of 11 campaigns
covering the tropics, midlatitudes and the Arctic,
consistently processed and considered more robust in their
measurements of small ice. For the fitting, we implement an
established approach to PSD parameterizations, which
consists of finding an adequate set of parameters for a
modified gamma function after normalization of both PSD
axes. These parameters are constrained to match in situ
measurements when predicting microphysical properties from
the PSDs, via a cost function minimization method. We
selected the ice water content and the ice crystal number
concentration, which are currently key parameters for modern
satellite retrievals and model microphysics schemes. We
found that a bimodal parameterization yields better results
than a monomodal one. The bimodal parameterization has a
lower spread for almost all ice crystal sizes over the
entire range of analyzed temperatures and fits better the
observations, especially for particles between 20 and about
110 µm at temperatures between −60 and −20 ∘C.
For this temperature range, the root mean square error for
the retrieved Nice is reduced from 0.36 to 0.20. This
demonstrates a clear advantage to considering the bimodality
of PSDs, e.g., for satellite retrievals.},
cin = {IEK-7},
ddc = {550},
cid = {I:(DE-Juel1)IEK-7-20101013},
pnm = {2112 - Climate Feedbacks (POF4-211)},
pid = {G:(DE-HGF)POF4-2112},
typ = {PUB:(DE-HGF)16},
UT = {WOS:001189421800001},
doi = {10.5194/acp-24-1699-2024},
url = {https://juser.fz-juelich.de/record/1022543},
}