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| Titel |
Should you use a simple or complex model for moisture recycling and atmospheric water tracing? |
| VerfasserIn |
Ruud van der Ent, Obbe Tuinenburg, Hans-Richard Knoche, Harald Kunstmann, Hubert Savenije |
| Konferenz |
EGU General Assembly 2013
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250073657
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| Zusammenfassung |
| This paper compares three state-of-the-art atmospheric water tracing models. Such models
are typically used to study the water component of the coupling between the land surface and
the atmosphere: moisture recycling and the source-sink relations of evaporation and
precipitation. However, the applicability of the many atmospheric water tracing methods used
in this field is unclear. In this paper, the RCM-tag method uses highly accurate 3D water
tracing (including phase transitions) directly within a regional climate model (online), while
the other two methods (WAM and 3D-T) use a posteriori (offline) water vapour tracing.
The methods are compared based on their basic characteristics, such as required
input data and computation speed. The a posteriori models are faster and more
flexible, but less accurate than the online model used here. In order to evaluate
the accuracy of the a posteriori models in detail, we apply tagging to evaporated
water from Lake Volta in West Africa and trace it to where it precipitates. It is
found that the strong wind shear in West Africa is the main cause of errors in the a
posteriori models. The number of vertical layers and the initial release height of
tagged water in the model are found to have the most significant influences on the
results. With this knowledge small improvements were made to the a posteriori
models. It appeared that expanding WAM to a 2 layer model, or a lower release
height in 3D-T, led to significantly better results. Finally, we introduce a simple
metric to assess wind shear globally and give recommendations about when to use
which model. The ‘best’ method, however, is very much dependent on the spatial
extent of the research question as well as the computation power at one’s disposal. |
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