Arctic clouds in ECHAM6 and their sensitivity to cloud microphysics and surface fluxes
Compared to other climate models, the MPI-ESM/ECHAM6 is one of the few models that is able to realistically simulate the typical two-state radiative structure of the Arctic boundary layer and also is able to sustain liquid water at low temperatures as is often observed in high latitudes. To identify...
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ftdoajarticles:oai:doaj.org/article:fb24a5f8c45a4f17a5b83de84c92ac80 2023-05-15T14:54:25+02:00 Arctic clouds in ECHAM6 and their sensitivity to cloud microphysics and surface fluxes J. Kretzschmar M. Salzmann J. Mülmenstädt J. Quaas 2019-08-01T00:00:00Z https://doi.org/10.5194/acp-19-10571-2019 https://doaj.org/article/fb24a5f8c45a4f17a5b83de84c92ac80 EN eng Copernicus Publications https://www.atmos-chem-phys.net/19/10571/2019/acp-19-10571-2019.pdf https://doaj.org/toc/1680-7316 https://doaj.org/toc/1680-7324 doi:10.5194/acp-19-10571-2019 1680-7316 1680-7324 https://doaj.org/article/fb24a5f8c45a4f17a5b83de84c92ac80 Atmospheric Chemistry and Physics, Vol 19, Pp 10571-10589 (2019) Physics QC1-999 Chemistry QD1-999 article 2019 ftdoajarticles https://doi.org/10.5194/acp-19-10571-2019 2022-12-31T02:41:06Z Compared to other climate models, the MPI-ESM/ECHAM6 is one of the few models that is able to realistically simulate the typical two-state radiative structure of the Arctic boundary layer and also is able to sustain liquid water at low temperatures as is often observed in high latitudes. To identify processes in the model that are responsible for the abovementioned features, we compare cloud properties from ECHAM6 to observations from CALIPSO-GOCCP using the COSP satellite simulator and perform sensitivity runs. The comparison shows that the model is able to reproduce the spatial distribution and cloud amount in the Arctic to some extent but a positive bias in cloud fraction is found in high latitudes, which is related to an overestimation of low- and high-level clouds. We mainly focus on low-level clouds and show that the overestimated cloud amount is connected to surfaces that are covered with snow or ice and is mainly caused by an overestimation of liquid-containing clouds. The overestimated amount of Arctic low-level liquid clouds can be related to insufficient efficiency of the Wegener–Bergeron–Findeisen (WBF) process but revising this process alone is not sufficient to improve cloud phase on a global scale as it also introduces a negative bias over oceanic regions in high latitudes. Additionally, this measure transformed the positive bias in low-level liquid clouds into a positive bias of low-level ice clouds, keeping the amount of low-level clouds almost unchanged. To avoid this spurious increase in ice clouds, we allowed for supersaturation with respect to ice using a temperature-weighted scheme for saturation vapor pressure but this measure, together with a more effective WBF process, might already be too efficient at removing clouds as it introduces a negative cloud cover bias. We additionally explored the sensitivity of low-level cloud cover to the strength of surface heat fluxes; by increasing surface mixing, the observed cloud cover and cloud phase bias could also be reduced. As ECHAM6 already mixes ... Article in Journal/Newspaper Arctic Directory of Open Access Journals: DOAJ Articles Arctic Atmospheric Chemistry and Physics 19 16 10571 10589 |
institution |
Open Polar |
collection |
Directory of Open Access Journals: DOAJ Articles |
op_collection_id |
ftdoajarticles |
language |
English |
topic |
Physics QC1-999 Chemistry QD1-999 |
spellingShingle |
Physics QC1-999 Chemistry QD1-999 J. Kretzschmar M. Salzmann J. Mülmenstädt J. Quaas Arctic clouds in ECHAM6 and their sensitivity to cloud microphysics and surface fluxes |
topic_facet |
Physics QC1-999 Chemistry QD1-999 |
description |
Compared to other climate models, the MPI-ESM/ECHAM6 is one of the few models that is able to realistically simulate the typical two-state radiative structure of the Arctic boundary layer and also is able to sustain liquid water at low temperatures as is often observed in high latitudes. To identify processes in the model that are responsible for the abovementioned features, we compare cloud properties from ECHAM6 to observations from CALIPSO-GOCCP using the COSP satellite simulator and perform sensitivity runs. The comparison shows that the model is able to reproduce the spatial distribution and cloud amount in the Arctic to some extent but a positive bias in cloud fraction is found in high latitudes, which is related to an overestimation of low- and high-level clouds. We mainly focus on low-level clouds and show that the overestimated cloud amount is connected to surfaces that are covered with snow or ice and is mainly caused by an overestimation of liquid-containing clouds. The overestimated amount of Arctic low-level liquid clouds can be related to insufficient efficiency of the Wegener–Bergeron–Findeisen (WBF) process but revising this process alone is not sufficient to improve cloud phase on a global scale as it also introduces a negative bias over oceanic regions in high latitudes. Additionally, this measure transformed the positive bias in low-level liquid clouds into a positive bias of low-level ice clouds, keeping the amount of low-level clouds almost unchanged. To avoid this spurious increase in ice clouds, we allowed for supersaturation with respect to ice using a temperature-weighted scheme for saturation vapor pressure but this measure, together with a more effective WBF process, might already be too efficient at removing clouds as it introduces a negative cloud cover bias. We additionally explored the sensitivity of low-level cloud cover to the strength of surface heat fluxes; by increasing surface mixing, the observed cloud cover and cloud phase bias could also be reduced. As ECHAM6 already mixes ... |
format |
Article in Journal/Newspaper |
author |
J. Kretzschmar M. Salzmann J. Mülmenstädt J. Quaas |
author_facet |
J. Kretzschmar M. Salzmann J. Mülmenstädt J. Quaas |
author_sort |
J. Kretzschmar |
title |
Arctic clouds in ECHAM6 and their sensitivity to cloud microphysics and surface fluxes |
title_short |
Arctic clouds in ECHAM6 and their sensitivity to cloud microphysics and surface fluxes |
title_full |
Arctic clouds in ECHAM6 and their sensitivity to cloud microphysics and surface fluxes |
title_fullStr |
Arctic clouds in ECHAM6 and their sensitivity to cloud microphysics and surface fluxes |
title_full_unstemmed |
Arctic clouds in ECHAM6 and their sensitivity to cloud microphysics and surface fluxes |
title_sort |
arctic clouds in echam6 and their sensitivity to cloud microphysics and surface fluxes |
publisher |
Copernicus Publications |
publishDate |
2019 |
url |
https://doi.org/10.5194/acp-19-10571-2019 https://doaj.org/article/fb24a5f8c45a4f17a5b83de84c92ac80 |
geographic |
Arctic |
geographic_facet |
Arctic |
genre |
Arctic |
genre_facet |
Arctic |
op_source |
Atmospheric Chemistry and Physics, Vol 19, Pp 10571-10589 (2019) |
op_relation |
https://www.atmos-chem-phys.net/19/10571/2019/acp-19-10571-2019.pdf https://doaj.org/toc/1680-7316 https://doaj.org/toc/1680-7324 doi:10.5194/acp-19-10571-2019 1680-7316 1680-7324 https://doaj.org/article/fb24a5f8c45a4f17a5b83de84c92ac80 |
op_doi |
https://doi.org/10.5194/acp-19-10571-2019 |
container_title |
Atmospheric Chemistry and Physics |
container_volume |
19 |
container_issue |
16 |
container_start_page |
10571 |
op_container_end_page |
10589 |
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