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Investigations of boundary layer structure, cloud characteristics and vertical mixing of aerosols at Barbados with large eddy simulations

Jähn, Michael and Muñoz-Esparza, Domingo and Chouza Keil, Fernando and Reitebuch, Oliver and Knoth, Oswald and Haarig, Moritz and Ansmann, Albert (2016) Investigations of boundary layer structure, cloud characteristics and vertical mixing of aerosols at Barbados with large eddy simulations. Atmospheric Chemistry and Physics, pp. 651-674. Copernicus Publications. DOI: 10.5194/acp-16-651-2016 ISSN 1680-7316

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Official URL: http://www.atmos-chem-phys.net/16/651/2016/acp-16-651-2016.html


Large eddy simulations (LESs) 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. Due to the presence of a topographically structured island surface in the domain center, the model setup has to be designed with open lateral boundaries. 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. In this work, this method is for the first time tested and validated for moist boundary layer simulations with open lateral boundary conditions. Observational data obtained from the SALTRACE field campaign is used for both model initialization and a comparison with Doppler wind and Raman lidar data. Several numerical sensitivity tests are carried out to demonstrate the problems related to “gray zone modeling” when using coarser spatial grid spacings beyond the inertial subrange of three-dimensional turbulence or when the turbulent marine boundary layer flow is replaced by laminar winds. Especially cloud properties in the downwind area west of Barbados are markedly affected in these kinds of simulations. Results of an additional simulation with a strong trade-wind inversion reveal its effect on cloud layer depth and location. 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 wind lidar data show similarities in the downwind vertical wind structure. Additionally, the model results accurately reproduce the development of the daytime convective boundary layer measured by the Raman lidar.

Item URL in elib:https://elib.dlr.de/102370/
Document Type:Article
Title:Investigations of boundary layer structure, cloud characteristics and vertical mixing of aerosols at Barbados with large eddy simulations
AuthorsInstitution or Email of AuthorsAuthors ORCID iD
Jähn, MichaelIfT, LeipzigUNSPECIFIED
Muñoz-Esparza, DomingoLos Alamos National Laboratory, EESUNSPECIFIED
Chouza Keil, FernandoDLR, IPAUNSPECIFIED
Knoth, OswaldIfT, LeipzigUNSPECIFIED
Haarig, MoritzIfT, LeipzigUNSPECIFIED
Ansmann, AlbertIfT, LeipzigUNSPECIFIED
Date:21 January 2016
Journal or Publication Title:Atmospheric Chemistry and Physics
Refereed publication:Yes
Open Access:Yes
Gold Open Access:Yes
In ISI Web of Science:Yes
DOI :10.5194/acp-16-651-2016
Page Range:pp. 651-674
Publisher:Copernicus Publications
Keywords:LES, DWL, ABL, Boundary layer, Vertical mixing, SALTRACE
HGF - Research field:Aeronautics, Space and Transport
HGF - Program:Space
HGF - Program Themes:Earth Observation
DLR - Research area:Raumfahrt
DLR - Program:R EO - Erdbeobachtung
DLR - Research theme (Project):R - Projekt ADM
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Lidar
Deposited By: Chouza Keil, Fernando German
Deposited On:25 Jan 2016 09:18
Last Modified:02 May 2019 14:05

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