Simulated and observed horizontal inhomogeneities of optical thickness of Arctic stratus
<p>Two-dimensional horizontal fields of cloud optical thickness <i>τ</i> derived from airborne measurements of solar spectral, cloud-reflected radiance are compared with semi-idealized large eddy simulations (LESs) of Arctic stratus performed with the Consortium for Small-scale...
| Main Authors: | , , , , |
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| Format: | Article |
| Language: | English |
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Copernicus Publications
2018-09-01
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| Series: | Atmospheric Chemistry and Physics |
| Online Access: | https://www.atmos-chem-phys.net/18/13115/2018/acp-18-13115-2018.pdf |
| _version_ | 1818017291391991808 |
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| author | M. Schäfer M. Schäfer K. Loewe K. Loewe A. Ehrlich C. Hoose M. Wendisch |
| author_facet | M. Schäfer M. Schäfer K. Loewe K. Loewe A. Ehrlich C. Hoose M. Wendisch |
| author_sort | M. Schäfer |
| collection | DOAJ |
| description | <p>Two-dimensional horizontal fields of cloud optical thickness <i>τ</i> derived
from airborne measurements of solar spectral, cloud-reflected radiance are
compared with semi-idealized large eddy simulations (LESs) of Arctic
stratus performed with the Consortium for Small-scale Modeling
(COSMO) atmospheric model. The measurements were collected during the
Vertical Distribution of Ice in Arctic Clouds (VERDI) campaign carried out in
Inuvik, Canada, in April/May 2012. The input for the LESs is obtained from
collocated airborne dropsonde observations of a persistent Arctic stratus
above the sea-ice-free Beaufort Sea. Simulations are performed for spatial
resolutions of 50 m (1.6 km  ×  1.6 km domain) and 100 m
(6.4 km  ×  6.4 km domain). Macrophysical cloud properties, such as
cloud top altitude and vertical extent, are well captured by the COSMO
simulations. However, COSMO produces rather homogeneous clouds compared to
the measurements, in particular for the simulations with coarser spatial
resolution. For both spatial resolutions, the directional structure of the
cloud inhomogeneity is well represented by the model. Differences between the
individual cases are mainly associated with the wind shear near cloud top and
the vertical structure of the atmospheric boundary layer. A sensitivity study
changing the wind velocity in COSMO by a vertically constant scaling factor
shows that the directional, small-scale cloud inhomogeneity structures can
range from 250 to 800 m, depending on the mean wind speed, if the simulated
domain is large enough to capture also large-scale structures, which then
influence the small-scale structures. For those cases, a threshold wind
velocity is identified, which determines when the cloud inhomogeneity stops
increasing with increasing wind velocity.</p> |
| first_indexed | 2024-04-14T07:25:12Z |
| format | Article |
| id | doaj.art-22e2b62d408c43da93a59ac1175823c8 |
| institution | Directory Open Access Journal |
| issn | 1680-7316 1680-7324 |
| language | English |
| last_indexed | 2024-04-14T07:25:12Z |
| publishDate | 2018-09-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Atmospheric Chemistry and Physics |
| spelling | doaj.art-22e2b62d408c43da93a59ac1175823c82022-12-22T02:06:02ZengCopernicus PublicationsAtmospheric Chemistry and Physics1680-73161680-73242018-09-0118131151313310.5194/acp-18-13115-2018Simulated and observed horizontal inhomogeneities of optical thickness of Arctic stratusM. Schäfer0M. Schäfer1K. Loewe2K. Loewe3A. Ehrlich4C. Hoose5M. Wendisch6Leipzig Institute for Meteorology, University of Leipzig, Leipzig, GermanyThese authors contributed equally to this work.Institute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Karlsruhe, GermanyThese authors contributed equally to this work.Leipzig Institute for Meteorology, University of Leipzig, Leipzig, GermanyInstitute of Meteorology and Climate Research, Karlsruhe Institute of Technology, Karlsruhe, GermanyLeipzig Institute for Meteorology, University of Leipzig, Leipzig, Germany<p>Two-dimensional horizontal fields of cloud optical thickness <i>τ</i> derived from airborne measurements of solar spectral, cloud-reflected radiance are compared with semi-idealized large eddy simulations (LESs) of Arctic stratus performed with the Consortium for Small-scale Modeling (COSMO) atmospheric model. The measurements were collected during the Vertical Distribution of Ice in Arctic Clouds (VERDI) campaign carried out in Inuvik, Canada, in April/May 2012. The input for the LESs is obtained from collocated airborne dropsonde observations of a persistent Arctic stratus above the sea-ice-free Beaufort Sea. Simulations are performed for spatial resolutions of 50 m (1.6 km  ×  1.6 km domain) and 100 m (6.4 km  ×  6.4 km domain). Macrophysical cloud properties, such as cloud top altitude and vertical extent, are well captured by the COSMO simulations. However, COSMO produces rather homogeneous clouds compared to the measurements, in particular for the simulations with coarser spatial resolution. For both spatial resolutions, the directional structure of the cloud inhomogeneity is well represented by the model. Differences between the individual cases are mainly associated with the wind shear near cloud top and the vertical structure of the atmospheric boundary layer. A sensitivity study changing the wind velocity in COSMO by a vertically constant scaling factor shows that the directional, small-scale cloud inhomogeneity structures can range from 250 to 800 m, depending on the mean wind speed, if the simulated domain is large enough to capture also large-scale structures, which then influence the small-scale structures. For those cases, a threshold wind velocity is identified, which determines when the cloud inhomogeneity stops increasing with increasing wind velocity.</p>https://www.atmos-chem-phys.net/18/13115/2018/acp-18-13115-2018.pdf |
| spellingShingle | M. Schäfer M. Schäfer K. Loewe K. Loewe A. Ehrlich C. Hoose M. Wendisch Simulated and observed horizontal inhomogeneities of optical thickness of Arctic stratus Atmospheric Chemistry and Physics |
| title | Simulated and observed horizontal inhomogeneities of optical thickness of Arctic stratus |
| title_full | Simulated and observed horizontal inhomogeneities of optical thickness of Arctic stratus |
| title_fullStr | Simulated and observed horizontal inhomogeneities of optical thickness of Arctic stratus |
| title_full_unstemmed | Simulated and observed horizontal inhomogeneities of optical thickness of Arctic stratus |
| title_short | Simulated and observed horizontal inhomogeneities of optical thickness of Arctic stratus |
| title_sort | simulated and observed horizontal inhomogeneities of optical thickness of arctic stratus |
| url | https://www.atmos-chem-phys.net/18/13115/2018/acp-18-13115-2018.pdf |
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