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| Titel |
Implementing surface parameter aggregation rules in the CCM3 global climate model: regional responses at the land surface |
| VerfasserIn |
M. A. Arain, E. J. Burke, Z.-L. Yang, W. J. Shuttleworth |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1027-5606
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| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 3, no. 4 ; Nr. 3, no. 4, S.463-476 |
| Datensatznummer |
250001184
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| Publikation (Nr.) |
 copernicus.org/hess-3-463-1999.pdf |
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| Zusammenfassung |
| The
land-surface parameters required as input to a GCM grid box (typically a few
degrees) are often set to be those of the dominant vegetation type within the
grid box. This paper discusses the use and effect of aggregation rules for
specifying effective values of these land cover parameters by taking into
account the relative proportion of each land-cover type within each individual
grid box. Global land-cover classification data at 1 km resolution were used to
define Biosphere Atmosphere Transfer Scheme (BATS) specific aggregate (using
aggregation rules) land-cover parameters. Comparison of the values of the
aggregate parameters and those defined using the single dominant vegetation type
(default parameters) shows significant differences in some regions, particularly
in the semi-desert and in forested regions, e.g. the Sahara Desert and the
tropical forest of South America. These two different sets of parameters were
used as input data for two 10-year simulations of the NCAR CCM3 model coupled to
the BATS land-surface scheme. Statistical analyses comparing the results of the
two model runs showed that the resulting effects on the land-surface diagnostics
are significant only in specific regions. For example, the sensible heat flux in
the Sahara Desert calculated for the aggregate parameter run increased due to
the marked increase in the minimum stomatal resistance and the decrease in
fractional vegetation cover in the aggregate parameters over the default
parameters. The modelled global precipitation and surface air temperature fields
were compared to observations: there is a general improvement in the performance
of the aggregate parameter run over the default parameter run in areas where the
differences between the aggregate and default parameter run are significant.
However, most of the difference between the modelled and observed fields is
attributable to other model deficiencies. It can be concluded that the use of
aggregation rules to derive land-surface parameters results in significant
changes in modelled climate and in some improvements in the land-surface
diagnostics in selected regions. There is also some evidence that there is a
response in the global circulation pattern, which is a focus of further work. |
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