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| Titel |
Validation of the large-scale Lagrangian cirrus model CLaMS-Ice by in-situ measurements |
| VerfasserIn |
Anja Costa, Christian Rolf, Jens-Uwe Grooß, Armin Afchine, Nicole Spelten, Volker Dreiling, Martin Zöger, Martina Krämer |
| Konferenz |
EGU General Assembly 2015
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 17 (2015) |
| Datensatznummer |
250108933
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| Publikation (Nr.) |
 EGU/EGU2015-8777.pdf |
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| Zusammenfassung |
| Cirrus clouds are an element of uncertainty in the climate system and have received
increasing attention since the last IPCC reports. The interaction of varying freezing
meachanisms, sedimentation rates, temperature and updraft velocity fluctuations and other
factors that lead to the formation of those clouds is still not fully understood. During the
ML-Cirrus campaign 2014 (Germany), the new cirrus cloud model CLaMS-Ice (see Rolf et
al., EGU 2015) has been used for flight planning to direct the research aircraft HALO into
interesting cirrus cloud regions. Now, after the campaign, we use our in-situ aircraft
measurements to validate and improve this model – with the long-term goal to enable it to
simulate cirrus cloud cover globally, with reasonable computing times and sufficient
accuracy.
CLaMS-Ice consists of a two-moment bulk model established by Spichtinger
and Gierens (2009a, 2009b), which simulates cirrus clouds along trajectories that
the Lagrangian model CLaMS (McKenna et al., 2002 and Konopka et al. 2007)
derived from ECMWF data. The model output covers temperature, pressure, relative
humidity, ice water content (IWC), and ice crystal numbers (Nice). These parameters
were measured on board of HALO by the following instruments: temperature and
pressure by BAHAMAS, total and gas phase water by the hygrometers FISH and
SHARC (see Meyer et al 2014, submitted to ACP), and Nice as well as ice crystal size
distributions by the cloud spectrometer NIXE-CAPS (see also Krämer et al., EGU
2015).
Comparisons of the model results with the measurements yield that cirrus clouds can be
successfully simulated by CLaMS-Ice. However, there are sections in which the model’s
relative humidity and Nice deviate considerably from the measured values. This can be traced
back to e.g. the initialization of total water from ECMWF data. The simulations are therefore
reinitiated with the total water content measured by FISH. Other possible sources of
uncertainties are investigated, as imposed temperature fluctuations, numbers and
efficencies of heterogeneous ice nuclei or assumptions concerning the sedimentation
rates.
This contribution sums up the results of these investigations and outlines future work on
CLaMS-Ice, that will lead to a tool helping to understand the cirrus clouds under the different
environmental conditions during ML-Cirrus. |
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