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| Titel |
Investigating mixed phase clouds using a synergy of ground based remote
sensing measurements |
| VerfasserIn |
Rosa Gierens, Stefan Kneifel, Ulrich Löhnert |
| Konferenz |
EGU General Assembly 2017
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 19 (2017) |
| Datensatznummer |
250152456
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| Publikation (Nr.) |
 EGU/EGU2017-17295.pdf |
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| Zusammenfassung |
| Low level mixed phase clouds occur frequently in the Arctic, and can persist from hours to
several days. However, the processes that lead to the commonality and persistence of these
clouds are not well understood. The aim of our work is to get a more detailed understanding
of the dynamics of and the processes in Arctic mixed phase clouds using a combination of
instruments operating at the AWIPEV station in Svalbard. In addition, an aircraft
campaign collecting in situ measurements inside mixed phase clouds above the
station is planned for May-June 2017. The in situ data will be used for developing
and validating retrievals for microphysical properties from Doppler cloud radar
measurements. Once observational data for cloud properties is obtained, it can be used for
evaluating model performance, for studies combining modeling and observational
approaches, and eventually lead to developing model parameterizations of mixed phase
microphysics.
To describe the low-level mixed phase clouds, and the atmospheric conditions
in which they occur, we present a case study of a persistent mixed phase cloud
observed above the AWIPEV station. In the frame of the Arctic Amplification:
Climate Relevant Atmospheric and Surface Processes and Feedback Mechanisms
((AC)3) -project, a millimeter wavelength cloud radar was installed at the site in June
2016. The high vertical (4 m in the lowest layer) and temporal (2.5 sec) resolution
allows for a detailed description of the structure of the cloud. In addition to radar
reflectivity and mean vertical velocity, we also utilize the higher moments of the Doppler
spectra, such as skewness and kurtosis. To supplement the radar measurements, a
ceilometer is used to detect liquid layers inside the cloud. Liquid water path and
integrated water vapor are estimated using a microwave radiometer, which together
with soundings can also provide temperature and humidity profiles in the lower
troposphere. Moreover, a three-dimensional wind field is be obtained from a Doppler wind
lidar.
Furthermore, the Cloudnet scheme (www.cloud-net.org), that combines radar, lidar and
microwave radiometer observations with a forecast model to provide a best estimate of cloud
properties, is used for identifying mixed phase clouds. The continuous measurements
carried out at AWIPEV make it possible to characterize the macro- and micro-
physical properties of mixed-phase clouds on a long-term, statistical basis. The
Arctic observations are compared to a 5-year observational data set from Jülich
Observatory for Cloud Evolution (JOYCE) in Western Germany. The occurrence of
different types of clouds (with focus on mixed-phase and super-cooled clouds),
the distribution of ice and liquid within the clouds, the turbulent environment as
well as the temperatures where the different phases are occurring are investigated. |
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