Neutral

initial_soil_aerodynamic_resistance(u_24, z_obs=2)

Computes the aerodynamic resistance for soil without stability corrections \(r_{a,soil}^{0}\).

\[r_{a,soil}^{0}=\frac{\ln\left(\frac{z_{obs}}{z_{0,soil}}\right) \cdot \ln\left(\frac{z_{obs}}{0.1z_{0,soil}}\right)} {k^{2} \cdot u_{obs}}\]

where the following constants are used

• \(z_{0,soil}\) soil roughness = 0.001 [m]

• \(k\) = karman constant = 0.41 [-]

The factor 0.1 is the ratio between the surface roughness for momentum and heat.

Parameters

• u_24 (float) – daily wind speed at observation height, \(u_{obs}\) [m/s]

• z_obs (float) – observation height, \(z_{obs}\) [m]

Returns

ra_soil_init – aerodynamic resistance without stability corrections, \(r_{a,soil}^{0}\) [s/m]

Return type

float

initial_daily_evaporation(rn_24_soil, g0_24, ssvp_24, ad_24, vpd_24, psy_24, r_soil, ra_soil_init)

Computes the soil evaporation based on the Penman Monteith equation adapted for soil.

\[E^{0}=\frac{\Delta\left(Q_{soil}^{*}-G\right)+\rho c_{p} \frac{\Delta_{e}}{r_{a,soil}}}{\Delta+ \gamma\left(1+\frac{r_{soil}}{r_{a,soil}}\right)}\]

where the following constants are used

• \(c_{p}\) specific heat for dry air = 1004 [J kg-1 K-1]

• \(k\) = karman constant = 0.41 [-]

Parameters

• rn_24_soil (float) – daily net radiation for soil, \(Q_{soil}^{*}\) [W m-2]

• g0_24 (float) – daily soil heat flux, \(G\) [W m-2]

• ssvp_24 (float) – daily slope of saturated vapour pressure curve \(\Delta\) [mbar K-1]

• ad_24 (float) – daily air density, \(\rho\) [kg m-3]

• vpd_24 (float) – daily vapour pressure deficit, \(\Delta_{e}\) [mbar]

• psy_24 (float) – daily psychrometric constant, \(\gamma\) [mbar K-1]

• r_soil (float) – soil resistance, \(r_{soil}\) [m s-1]

• ra_soil_init (float) – initial soil aerodynamic resistance, \(r_{a,soil}\) [m s-1]

Returns

e_24_init – initial estimate radiation equivalent daily evaporation, \(E^{0}\) [W m-2]

Return type

float

initial_daily_evaporation_mm(e_24_init, lh_24)

Computes the soil evaporation based on the Penman Monteith equation adapted for soil.

\[E^{0}=E^{0} \cdot d_{sec} \cdot \lambda_{24}\]

where the following constants are used

• \(d_{sec}\) seconds in the day = 86400 [s]

Parameters

• e_24_init (float) – initial estimate daily evaporation, \(E^{0}\) [W m-2]

• lh_24 (float) – daily latent heat of evaporation, \(\lambda_{24}\) [J/kg]

Returns

e_24_init_mm – initial estimate daily evaporation in mm, \(E^{0}\) [mm d-1]

Return type

float

initial_canopy_aerodynamic_resistance(u_24, z0m, z_obs=2)

Computes the aerodynamic resistance for a canopy soil without stability corrections \(r_{a,}^{0}\).

\[r_{a,canopy}^{0}=\frac{\ln\left(\frac{z_{obs}}{z_{0,m}}\right) \cdot \ln \left(\frac{z_{obs}}{0.1z_{0,m}}\right)}{k^{2} \cdot u_{obs}}\]

where the following constants are used

• \(k\) = karman constant = 0.41 [-]

The factor 0.1 is the ratio between the surface roughness for momentum and heat.

Parameters

• u_24 (float) – daily wind speed at observation height, \(u_{obs}\) [m/s]

• z0m (float) – roughness length, \(z_{0,m}\) [m]

• z_obs (float) – observation height, \(z_{obs}\) [m]

Returns

ra_canopy_init – canopy resistance without stability corrections, \(r_{a,canopy}^{0}\) [s/m]

Return type

float

initial_daily_transpiration(rn_24_canopy, ssvp_24, ad_24, vpd_24, psy_24, r_canopy, ra_canopy_init)

Computes the soil evaporation based on the Penman Monteith equation adapted for soil.

\[T_{0}=\frac{\Delta\left(Q_{canopy}^{*}\right) +\rho c_{p}\frac{\Delta_{e}} {r_{a,canopy}}}{\Delta+ \gamma\left(1+\frac{r_{canopy}}{r_{a,canopy}}\right)}\]

where the following constants are used

• \(c_{p}\) specific heat for dry air = 1004 [J kg-1 K-1]

• \(k\) = karman constant = 0.41 [-]

Parameters

• rn_24_canopy (float) – daily net radiation for the canopy, \(Q_{soil}^{*}\) [W m-2]

• ssvp_24 (float) – daily slope of saturated vapour pressure curve \(\Delta\) [mbar K-1]

• ad_24 (float) – daily air density, \(\rho\) [kg m-3]

• vpd_24 (float) – daily vapour pressure deficit, \(\Delta_{e}\) [mbar]

• psy_24 (float) – daily psychrometric constant, \(\gamma\) [mbar K-1]

• r_canopy (float) – canopy resistance, \(r_{canopy}\) [m s-1]

• ra_canopy_init (float) – initial canopy aerodynamic resistance, \(r_{a,canopy}\) [m s-1]

Returns

t_24_init – initial estimate radiation equivalent daily transpiration, \(T^{0}\) [W m-2]

Return type

float

initial_daily_transpiration_mm(t_24_init, lh_24)

Computes the canopy transpiration based on the Penman Monteith equation adapted for canopy.

\[T^{0}=T^{0} \cdot d_{sec} \cdot \lambda_{24}\]

where the following constants are used

• \(d_{sec}\) seconds in the day = 86400 [s]

Parameters

• t_24_init (float) – initial estimate daily transpiration, \(E^{0}\) [W m-2]

• lh_24 (float) – daily latent heat of evaporation, \(\lambda_{24}\) [J/kg]

Returns

t_24_init_mm – initial estimate daily transpiration in mm, \(T^{0}\) [mm d-1]

Return type

float