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| Titel |
An improved representation of physical permafrost dynamics in the JULES land-surface model |
| VerfasserIn |
S. Chadburn, E. Burke, R. Essery, J. Boike, M. Langer, M. Heikenfeld, P. Cox, P. Friedlingstein |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1991-959X
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| Digitales Dokument |
URL |
| Erschienen |
In: Geoscientific Model Development ; 8, no. 5 ; Nr. 8, no. 5 (2015-05-21), S.1493-1508 |
| Datensatznummer |
250116346
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| Publikation (Nr.) |
 copernicus.org/gmd-8-1493-2015.pdf |
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| Zusammenfassung |
It is important to correctly simulate permafrost in global climate models, since the
stored carbon represents the source of a potentially important climate feedback.
This carbon feedback depends on the physical state of the permafrost.
We have therefore included improved physical permafrost processes in JULES (Joint UK
Land Environment Simulator), which is the land-surface
scheme used in the Hadley Centre climate models.
The thermal and hydraulic properties of the soil were modified to account for the presence
of organic matter, and the insulating effects of a surface layer of moss were added, allowing
for fractional moss cover. These processes are particularly relevant in permafrost zones.
We also simulate a higher-resolution soil column and deeper soil, and include
an additional thermal column at the base of the soil to represent bedrock.
In addition, the snow scheme was improved to allow it to run with arbitrarily thin layers.
Point-site simulations at Samoylov Island, Siberia, show that the model is
now able to simulate soil temperatures and thaw depth much closer to the
observations. The root mean square error for the near-surface soil
temperatures reduces by approximately 30%, and the active layer thickness
is reduced from being over 1 m too deep to within 0.1 m of the observed
active layer thickness. All of the model improvements contribute to improving
the simulations, with organic matter having the single greatest impact. A new
method is used to estimate active layer depth more accurately using the
fraction of unfrozen water.
Soil hydrology and snow are investigated further by holding the soil
moisture fixed and adjusting the parameters to make the
soil moisture and
snow density match better with observations. The root mean square error in
near-surface soil temperatures is reduced by a further 20% as a result. |
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