Difference between revisions of "Module Basin"
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==Main Processes== | ==Main Processes== | ||
===Evapotranspiration=== | ===Evapotranspiration=== | ||
| − | + | Some water may disappear from the soil because of the evaporation and transpiration processes, which become a sink in soil water profile. These two processes, currently named Evapotranspiration may be modeled using the Penmann Monteith equation. | |
| − | + | ||
| + | <math> \overset{\text{Energy flux rate}}{\lambda_v E=\frac{\Delta R_n + \rho_a c_p \left( \delta q \right) g_a }{\Delta + \gamma \left ( 1 + g_a / g_s \right)}}~ \iff ~ \overset{\text{Volume flux rate}}{ET_o=\frac{\Delta R_n + \rho_a c_p \left( \delta q \right) g_a } { \left( \Delta + \gamma \left ( 1 + g_a / g_s \right) \right) \lambda_v }} | ||
| + | </math> | ||
| + | |||
| + | :''λ''<sub>v</sub> = Latent heat of vaporization. Energy required per unit mass of water vaporized. (J/g) | ||
| + | :''L''<sub>v</sub> = Volumetric latent heat of vaporization. Energy required per water volume vaporized. (''L''<sub>v</sub> = 2453 MJ m<sup>-3</sup>) | ||
| + | |||
| + | :''E'' = Mass water evapotranspiration rate (g s<sup>-1</sup> m<sup>-2</sup>) | ||
| + | :''ET''<sub>o</sub> = Water volume evapotranspired (m<sup>3</sup> s<sup>-1</sup> m<sup>-2</sup>) | ||
| + | |||
| + | :Δ = Rate of change of saturation specific humidity with air temperature. (Pa K<sup>-1</sup>) | ||
| + | :''R''<sub>n</sub> = Net irradiance (W m<sup>-2</sup>), the external source of energy flux | ||
| + | :''c''<sub>p</sub> = Specific heat capacity of air (J kg<sup>-1</sup> K<sup>-1</sup>) | ||
| + | :''ρ''<sub>a</sub> = dry air density (kg m<sup>-3</sup>) | ||
| + | :δ''e'' = vapor pressure deficit, or specific humidity (Pa) | ||
| + | :''g''<sub>a</sub> = Hydraulic conductivity of air, atmospheric conductance (m s<sup>-1</sup>) | ||
| + | :''g''<sub>s</sub> = Conductivity of stoma, surface conductance (m s<sup>-1</sup>) | ||
| + | :''γ'' = Psychrometric constant (''γ'' ≈ 66 Pa K<sup>-1</sup>) | ||
| + | |||
| + | All of these calculations about potential evapotranspiration are made in module Basin in MohiLand model. However, not all of the potential water that can be evaporated or transpirated will be in fact removed from the soil. The water that will really leave the soil through these processes is calculated in the Porous Media module. | ||
==Other Features== | ==Other Features== | ||
Revision as of 18:56, 7 February 2011
Contents
Overview
Main Processes
Evapotranspiration
Some water may disappear from the soil because of the evaporation and transpiration processes, which become a sink in soil water profile. These two processes, currently named Evapotranspiration may be modeled using the Penmann Monteith equation.
- λv = Latent heat of vaporization. Energy required per unit mass of water vaporized. (J/g)
- Lv = Volumetric latent heat of vaporization. Energy required per water volume vaporized. (Lv = 2453 MJ m-3)
- E = Mass water evapotranspiration rate (g s-1 m-2)
- ETo = Water volume evapotranspired (m3 s-1 m-2)
- Δ = Rate of change of saturation specific humidity with air temperature. (Pa K-1)
- Rn = Net irradiance (W m-2), the external source of energy flux
- cp = Specific heat capacity of air (J kg-1 K-1)
- ρa = dry air density (kg m-3)
- δe = vapor pressure deficit, or specific humidity (Pa)
- ga = Hydraulic conductivity of air, atmospheric conductance (m s-1)
- gs = Conductivity of stoma, surface conductance (m s-1)
- γ = Psychrometric constant (γ ≈ 66 Pa K-1)
All of these calculations about potential evapotranspiration are made in module Basin in MohiLand model. However, not all of the potential water that can be evaporated or transpirated will be in fact removed from the soil. The water that will really leave the soil through these processes is calculated in the Porous Media module.
