Model help:TopoFlow-Evaporation-Priestley Taylor: Difference between revisions
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Latest revision as of 17:17, 19 February 2018
TopoFlow-Evaporation-Priestley Taylor
This module is the evaporation process component (Priestley-Taylor method) for a D8-based, spatial hydrologic model.
Model introduction
This process component is part of a spatially-distributed hydrologic model called TopoFlow, but it can now be used as a stand-alone model.
Model parameters
Uses ports
• Meteorology
• Channels (surface water flow in a network of channels with trapezoidal cross-section)
• Snow (Snowmelt)
• Infil (Infiltration)
• Satzone (Subsurface flow in saturated zone)
Provides ports
• Evap (Evaporation)
• Configure (tabbed dialog GUI to change settings)
• Run (only if used as the Driver)
Main equations
- Evaporation rate
[math]\displaystyle{ ET=\left (1000 \ast Q_{et}\right) / \left (\rho_{water} \ast L_{v}\right) }[/math] (1)
- Energy flux used to evaporate water
[math]\displaystyle{ Q_{et}= \alpha \ast [ 0.406 + \left ( 0.011 \ast T_{air}\right)] \ast \left ( Q_{SW} + Q_{LW} - Q_{c}\right) }[/math] (2)
- Conduction energy flux
[math]\displaystyle{ Q_{c}= K_{soil} \ast \left (T_{soil_x} - T_{surf} \right) \ast \left ( 100 / x \right) }[/math] (3)
Symbol | Description | Unit |
---|---|---|
QSW | net shortwave radiation | [W / m2] |
QLW | net longwave radiation | [W / m2] |
Tair | air temperature | deg C |
Tsurf | surface (snow) temperature | deg C |
Tsoil_x | soil temperature at depth x | deg C |
x | reference depth in soil | m |
Ksoil | thermal conductivity of soil | W / (m deg_C ) |
α | coefficient | - |
Lv | latent heat of vaporization, water (2500000) | J /kg |
ρwater | density of water | kg / m3 |
ET | evaporation rate | mm / sec |
Qet | energy flux used to evaporate water | W / m2 |
Qc | conduction energy flux (between surf. and subsurf.) | W / m2 |
Ri | Rechardson's number | - |
Notes
Notes on Input Parameters
For each variable, you may choose from the droplist of data types. For the "Scalar" data type, enter a numeric value with the units indicated in the dialog. For the other data types, enter a filename. Values in files must also use the indicated units.
Single grids and grid sequences are assumed to be stored as RTG and RTS files, respectively. Time series are assumed to be stored as text files, with one value per line. For a time series or grid sequence, the time between values must coincide with the timestep provided.
If net total radiation has been measured, it can be entered as QSW and then QLW can be set to zero. Any meteorological variables entered here (such as Tair) are automatically shared with other other processes, such as Snowmelt and Precipitation.
Notes on the Equations
All variables and their units can be seen by expanding the Nomenclature section above.
Wherever (d > 0), evaporation results in a reduction in the surface flow depth. Wherever (d = 0), water is removed from subsurface storage. If the 1D Richards' equation is used for infiltration, then the evaporation rate is applied as a surface boundary condition and alters the soil moisture profile accordingly.
Examples
An example run with input parameters, BLD files, as well as a figure / movie of the output
Follow the next steps to include images / movies of simulations:
- Upload file: https://csdms.colorado.edu/wiki/Special:Upload
- Create link to the file on your page: [[Image:<file name>]].
See also: Help:Images or Help:Movies
Developer(s)
References
Zhang, Z., D.L. Kane and L.D. Hinzman (2000) Development and application of a spatially-distributed Arctic hydrological and thermal process model (ARHYTHM), Hydrological Processes, 14, 1017-1044.
Links
Related Help Pages
Model Metadata