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LandscapeDNDC
1.36.0
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LandscapeDNDC
1.36.0
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The microclimate model CanopyECM calculates:
CanopyECM requires further models for:
Available options: Default options are marked with bold letters.
Calculates radiation in each canopy layer and beneath the canopy and absorbed radiation in sunlit and shaded canopy fractions as well as the fraction of sunlit foliage area.
The basic algorithms are taken from Spitters 1986 and complemented by Thornley 2002.
In contrast to traditional approaches, light extinction is accounted for separately layer by layer, considering changes in crown shape.
Note that the proceedure doesen't account for slope effects. A possible approach to address this might be that of Garnier and Ohmura (1968) also applied in Lexer & Hoenninger 2001.
Calculates vapor pressure deficit (mbar, or hPa) for the ground and every foliage layer.
VPD is calculated based on the canopy layer temperature. It is assumed that the absolute water content throughout the canopy is , constant but the saturated vapor pressure and thus the pressure deficit changes with temperature in every layer.
Calculates wind speed decline throughout the canopy according to [37]. However, the originally used dependency on leaf area has been replaced by one of plant area which also considers the impact of overall woody biomass.
Wind speed is calculated in each canopy layer (using cosh =Hyper Cosinus):
\[ loc\_{win}_{fl} = loc\_{win} \cdot \frac {cosh(ExtFac \frac {hCum - hBottom}{hTop})}{cosh(ExtFac \frac {1-hBottom}{hTop})}^{2.5} \]
with
| loc_{win}_{fl} | Foliage layer specific wind speed | (m s-1) |
| loc_{win} | Above-canopy wind speed | (m s-1) |
| hCum | Cumulative height | (m) |
| hBottom | Bottom height of tree crowns | (m) |
The extinction factor depends linearly on plant area index:
\[ extFac = \frac{ 4.0 \cdot DRAGC \cdot pai}{ROUGH^2 KARMAN^2} \]
\[ pai = lai + mWood \cdot FEXT_W \cdot exp(-0.1 \cdot lai) \]
with
| extFac | Extinction factor | (-) |
| DRAGC = 0.1 | Drag coefficient | (-) |
| ROUGH = 2.0 | Roughness parameter of the ground (1-2) | (-) |
| KARMAN = 0.41 | Karman constant (Hogstrom 1985) | (-) |
Albedo is the fraction of reflected light relative to the total incoming shortwave radiation.
\[ albedo = \frac { \sum_0^fl(sw\_{refl}_{fl}) + sw\_{refl}_{a} }{rad_sw} \]
\[ sw\_{refl}_{fl} = (rdiff_{fl} + rdir_{fl}) \cdot \frac {refl}{1.0-refl} \]
\[ refl = (pai \cdot 0.5) \cdot (1.0 - \frac { sqrt(1.0-ALB) } { 1.0 + sqrt(1.0-ALB) }; \]
with
The reflection from the soil surface is assumed to be a fixed proportion (FLITALB) of the shortwave radiation that is released below the last canopy layer. This is added to the reflected radiation of all canopy layers, which in turn are influenced by plant area (that is a function of foliage and wood biomass) distribution and a species-specific albedo parameter (ALB). If more than one species has leaves in the same layer, plant area and ALB are scaled with leaf area fraction of the respective species.
CanopyECM calculates a temperature buffering effect in the canopy as leaf area-weighed connection between temperature above the soil and temperature above the canopy (field temperature)
Temperature above the soil \( T_s \) depends on atmospheric temperature above canopy \( T_{atm} \), leaf area index and an empirical species - specific temperature damping parameter (CDAMP):
\begin{eqnarray*} bvc &= &\frac{LAI}{LAI + \text{CDAMP}} \\ T_s(t + 1) &= &bvc \cdot T_s(t) + (1 - bvc) T_ { atm } \end{eqnarray*}
Temperature within the canopy \( T_c \) is linearly correlated with canopy height \( z \) specific leaf area index:
\begin{eqnarray*} \phi(z) &=& \frac{\sum_0^z LAI}{\sum LAI} \\ T_c(z) &=& T_s + \phi (T_{atm} - T_s) \end{eqnarray*}
1.8.13