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| Titel |
Simulation of infiltration and redistribution of intense rainfall using Land Surface Models |
| VerfasserIn |
Anna Mueller, Anne Verhoef, Hannah Cloke |
| Konferenz |
EGU General Assembly 2016
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| Medientyp |
Artikel
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| Sprache |
en
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 18 (2016) |
| Datensatznummer |
250125054
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| Publikation (Nr.) |
 EGU/EGU2016-4580.pdf |
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| Zusammenfassung |
| Flooding from intense rainfall (FFIR) can cause widespread damage and disruption.
Numerical Weather Prediction (NWP) models provide distributed information about
atmospheric conditions, such as precipitation, that can lead to a flooding event. Short
duration, high intensity rainfall events are generally poorly predicted by NWP models,
because of the high spatiotemporal resolution required and because of the way the convective
rainfall is described in the model. The resolution of NWP models is ever increasing. Better
understanding of complex hydrological processes and the effect of scale is important in order
to improve the prediction of magnitude and duration of such events, in the context of disaster
management.
Working as part of the NERC SINATRA project, we evaluated how the Land Surface
Model (LSM) components of NWP models cope with high intensity rainfall input and
subsequent infiltration problems. Both in terms of the amount of water infiltrated in the soil
store, as well as the timing and the amount of surface and subsurface runoff generated. The
models investigated are SWAP (Soil Water Air Plant, Alterra, the Netherlands,
van Dam 1997), JULES (Joint UK Land Environment Simulator a component of
Unified Model in UK Met Office, Best et al. 2011) and CHTESSEL (Carbon and
Hydrology- Tiled ECMWF Scheme for Surface Exchanges over Land, Balsamo et al.
2009)
We analysed the numerical aspects arising from discontinuities (or sharp gradients) in
forcing and/or the model solution.
These types of infiltration configurations were tested in the laboratory (Vachaud 1971),
for some there are semi-analytical solutions (Philip 1957, Parlange 1972, Vanderborght 2005)
or reference numerical solutions (Haverkamp 1977, van Dam 2000, Vanderborght
2005).
The maximum infiltration by the surface, Imax, is in general dependent on atmospheric
conditions, surface type, soil type, soil moisture content θ, and surface orographic factor σ.
The models used differ in their approach to describe and deal with this top boundary
condition definition.
All three LSMs discretise the spatial derivative in the Richards equation (∂∕∂z) using
central finite differences, which is a 2nd order method, that according to Godunov’s theorem
is non-monotone. It is prone to producing non-physical oscillations in the solution. We
performed a mesh and timestep dependence study for hypothetical soil columns and showed
the presence of the oscillations in Jules and SWAP solutions. We also investigated the
rainfall/runoff partition and redistribution in case of intense rainfall using these three
models. |
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