Analysis of a two-layer cloud system with RAMS model and comparison to airborne observations |
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Authors: | Elias Mavromatidis Theodoros I Lekas George Kallos |
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Institution: | (1) School of Physics, Division of Applied Physics, National and Kapodistrian University of Athens, University Campus, Bldg PHYS-5, 15784 Athens, Attika, Greece;(2) Department of Aerodynamics and Flight Mechanics, Hellenic Air Force Academy, Dekelia Air Force Base, TGA 1010 Dekelia, Attika, Greece |
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Abstract: | A three-dimensional numerical model (Regional Atmospheric Modeling System—-RAMS) was used to study the formation and evolution
of water forms in a two-layer cloud structure observed during a field campaign over Brest (France). The model performance
in regular operations, using conventional meteorological data as initial and lateral boundary conditions, was also examined.
Remote sensing observations of the cloud system and in-situ aircraft data, selected during the campaign, were used to validate
the model outputs. The model simulations showed that the lower cloud formation was characterized by high number concentration
of pristine ice and snow, while the concentration of aggregates, graupel and hail were considerably lower. Hydrometeors in
liquid phase appeared demonstrating high number concentration and water content on the top of this layer. The upper cloud
layer consisted only of frozen water substances in lower amounts. The qualitative and quantitative comparison of the model-calculated
meteorological and microphysical fields to the available observational data revealed that the model reflected fairly well
the cloud structure (e.g., the spatio-temporal variability of the cloud parameters, the geometry of the cloud system). However,
there were deviations as far as the model underestimating the ice water content (IWC) and number concentration (Nt) fields is concerned, especially at the atmospheric layer between 2.5 and 4 km of altitude. These deviations of the model
simulated quantities from the measured ones may be attributed either to the performance of the model’s microphysics scheme,
to instrument inaccuracies and to the local disturbance caused by the aircraft. |
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Keywords: | Cloud microphysics Numerical modeling Hydrometeors Particle trajectories |
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