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| Titel |
Investigations of boundary layer structure, cloud characteristics and vertical mixing of aerosols at Barbados with large eddy simulations |
| VerfasserIn |
Michael Jähn, Domingo Muñoz-Esparza, Fernando Chouza, Oliver Reitebuch, Oswald Knoth, Moritz Haarig, Albert Ansmann, Ina Tegen |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250133524
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| Publikation (Nr.) |
 EGU/EGU2016-14144.pdf |
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| Zusammenfassung |
| Large eddy simulations (LESs) with ASAM (All Scale Atmospheric Model) are performed
for the area of the Caribbean island Barbados to investigate island effects on boundary layer
modification, cloud generation and vertical mixing of aerosols. In order to generate inflow
turbulence consistent with the upstream marine boundary layer forcing, we use the cell
perturbation method based on finite amplitude potential temperature perturbations. This
method is now also validated for moist boundary layer simulations with open lateral
boundary conditions.
Observational data obtained from the SALTRACE (Saharan Aerosol Long-range
Transport and Aerosol-Cloud-Interaction Experiment) field campaign is used for both
model initialization and comparisons. Several sensitivity tests are carried out to
demonstrate the problems related to “gray zone modeling” or when the turbulent
marine boundary layer flow is replaced by laminar winds. Additional simulation
cases deal with modified surface characteristics and their impacts on the simulation
results.
Saharan dust layers that reach Barbados via long-range transport over the North
Atlantic are included as passive tracers in the model. Effects of layer thinning,
subsidence and turbulent downward transport near the layer bottom at z ≈ 1800 m
become apparent. The exact position of these layers and strength of downward
mixing is found to be mainly controlled atmospheric stability (especially inversion
strength) and wind shear. Comparisons of LES model output with lidar data show
similarities in the downwind vertical wind structure and accurately reproduces the
development of the daytime convective boundary layer measured by the Raman lidar. |
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