Cloud chamber experiments on the origin of ice crystal complexity in cirrus clouds
This study reports on the origin of small-scale ice crystal complexity and its influence on the angular light scattering properties of cirrus clouds. Cloud simulation experiments were conducted at the AIDA (Aerosol Interactions and Dynamics in the Atmosphere) cloud chamber of the Karlsruhe Instit...
| Main Authors: | , , , , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2016-04-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/16/5091/2016/acp-16-5091-2016.pdf |
| Summary: | This study reports on the origin of small-scale ice crystal complexity and
its influence on the angular light scattering properties of cirrus clouds.
Cloud simulation experiments were conducted at the AIDA (Aerosol Interactions
and Dynamics in the Atmosphere) cloud chamber of the Karlsruhe Institute of
Technology (KIT). A new experimental procedure was applied to grow and
sublimate ice particles at defined super- and subsaturated ice conditions and
for temperatures in the −40 to −60 °C range. The
experiments were performed for ice clouds generated via homogeneous and
heterogeneous initial nucleation. Small-scale ice crystal complexity was
deduced from measurements of spatially resolved single particle light
scattering patterns by the latest version of the Small Ice Detector (SID-3).
It was found that a high crystal complexity dominates the microphysics of the
simulated clouds and the degree of this complexity is dependent on the
available water vapor during the crystal growth. Indications were found that
the small-scale crystal complexity is influenced by unfrozen
H<sub>2</sub>SO<sub>4</sub> / H<sub>2</sub>O residuals in the case of homogeneous
initial ice nucleation. Angular light scattering functions of the simulated
ice clouds were measured by the two currently available airborne polar
nephelometers: the polar nephelometer (PN) probe of Laboratoire de
Métérologie et Physique (LaMP) and the Particle Habit Imaging and
Polar Scattering (PHIPS-HALO) probe of KIT. The measured scattering functions
are featureless and flat in the side and backward scattering directions. It
was found that these functions have a rather low sensitivity to the
small-scale crystal complexity for ice clouds that were grown under typical
atmospheric conditions. These results have implications for the microphysical
properties of cirrus clouds and for the radiative transfer through these
clouds. |
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| ISSN: | 1680-7316 1680-7324 |