Call number:
AWI A7-24-95703
Description / Table of Contents:
The icosahedral non-hydrostatic large eddy model (ICON-LEM) was applied around the drift track of the Multidisciplinary Observatory Study of the Arctic (MOSAiC) in 2019 and 2020. The model was set up with horizontal grid-scales between 100m and 800m on areas with radii of 17.5km and 140 km. At its lateral boundaries, the model was driven by analysis data from the German Weather Service (DWD), downscaled by ICON in limited area mode (ICON-LAM) with horizontal grid-scale of 3 km.
The aim of this thesis was the investigation of the atmospheric boundary layer near the surface in the central Arctic during polar winter with a high-resolution mesoscale model. The default settings in ICON-LEM prevent the model from representing the exchange processes in the Arctic boundary layer in accordance to the MOSAiC observations. The implemented sea-ice scheme in ICON does not include a snow layer on sea-ice, which causes a too slow response of the sea-ice surface temperature to atmospheric changes. To allow the sea-ice surface to respond faster to changes in the atmosphere, the implemented sea-ice parameterization in ICON was extended with an adapted heat capacity term.
The adapted sea-ice parameterization resulted in better agreement with the MOSAiC observations. However, the sea-ice surface temperature in the model is generally lower than observed due to biases in the downwelling long-wave radiation and the lack of complex surface structures, like leads. The large eddy resolving turbulence closure yielded a better representation of the lower boundary layer under strongly stable stratification than the non-eddy-resolving turbulence closure. Furthermore, the integration of leads into the sea-ice surface reduced the overestimation of the sensible heat flux for different weather conditions.
The results of this work help to better understand boundary layer processes in the central Arctic during the polar night. High-resolving mesoscale simulations are able to represent temporally and spatially small interactions and help to further develop parameterizations also for the application in regional and global models.
Type of Medium:
Dissertations
Pages:
xii, 110 Seiten
,
Illustrationen, Diagramme
URL:
https://doi.org/10.25932/publishup-62437
URN:
urn:nbn:de:kobv:517-opus4-624374
DOI:
10.25932/publishup-62437
Language:
English
Note:
Dissertation, Universität Potsdam, 2023
,
Contents
1. Introduction
2. Boundary Layers Types of the Atmosphere
2.1. The Convective Boundary Layer (CBL)
2.2. The Neutral Boundary Layer (NBL)
2.3. The Stable Boundary Layer (SBL)
3. The Closure problem
4. Model description
4.1. Applied model versions
4.2. Governing equations
4.3. Horizontal grid
4.4. Vertical grid
4.5. Lateral boundaries
4.6. Parametrizations
4.6.1. Radiation scheme
4.6.2. Microphysics
4.6.3. Mellor-Yamada scheme
4.6.4. Smagorinsky scheme
4.6.5. Sea ice scheme
4.7. Difference to classical LES Models
5. Experimental Setup
6. MOSAiC Measurements
6.1. ARM Meteorological tower
6.2. Radiosondes
7. Model evaluation for the central Arctic
7.1. Impact of the horizontal resolution
7.1.1. Under cold, light wind conditions
7.1.2. Under stormy conditions
7.2. Impact of the sea-ice scheme
7.3. Impact of the lower boundary conditions
7.4. Impact of the parametrization schemes under cold, light wind conditions
7.4.1. Near-surface variables
7.4.2. Vertical profiles
7.4.3. Surface fluxes
7.4.4. Boundary Layer Height
7.5. Impact of the parametrization schemes under stormy conditions
7.5.1. Near-surface variables
7.5.2. Vertical profiles
7.5.3. Surface fluxes
7.5.4. Boundary Layer height
8. Discussion and Summary
Acknowledgements
Appendix
Location:
AWI Reading room
Branch Library:
AWI Library
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