const.ymlThis file lists all constants and their values used in ARCHIMED-φ. The file is optional. The example file provided below lists the default values used in ARCHIMED (their values are also provided in this page for information).
You can safely ignore this page for the vast majority of use cases. You don’t need to know or understand everything in this page, it is only provided for convenience in case the user has specific needs.
co2_to_heat_boundary_layer_conductance is used to convert the boundary layer conductance to heat into the boundary layer conductance to \(CO_2\) with the following equation. The default value is 1.32 as given in the MAESPA model, or in the bigleaf R package following Hicks et al. (1987):\[Gb_{CO_2}=\frac{Gb_{heat}}{co2\_to\_heat\_boundary\_layer\_conductance}\]
heat_to_water_boundary_layer_conductance is used to convert boundary layer conductance to heat into boundary layer conductance to water (default to 1.075):\[Gb_{H_2O}= Gb_{heat} \cdot heat\_to\_water\_boundary\_layer\_conductance\]
co2_to_water_conductance is used to convert a stomatal conductance to \(CO_2\) into a stomatal conductance for \(H_2O\) (default to 1.57):\[Gb_{H_2O}= Gb_{CO_2} \cdot co2\_to\_water\_conductance\]
forced_heat_BL_conductance_proportionality_factor is used compute the boundary layer conductance for heat under forced convection (default to 1000/3):\[Gbh_{forced} = \frac{\sqrt{\frac{wind}{specificLength}}}{C}\]
See Leuning et al. (1995) for more details (equation E1 from Appendix E).
atmospheric_CO2_concentration defines the default \(CO_2\) concentration in the atmosphere in ppm. It is used only if the \(CO_2\) variable is missing from the meteorology file (default to 400 ppm).
atmospheric_O2_concentration defines the \(O_2\) concentration in the atmosphere in ppm. Default to 210.0 ppm. It is used to compute the rubisco-limited carboxylation rate \(W_c\) (\(\mu mol_{CO_2} \cdot m^{-2} \cdot s^{-1}\)):
\[W_c = \frac{(Vc_{max} \cdot C_i)}{C_i + K_c \cdot (1.0 + \frac{atmospheric\_O2\_concentration}{K_o})}\] See Farquhar, von Caemmerer, and Berry (1980) for more details (equation 9).
water_vapour_to_dry_air_molecular_weight_ratio is used to convert molecular weight of water vapour into dry air. Default to 0.622. It is used to compute the psychrometric constant (\(\gamma\), in \(kPa \cdot °C^{-1}\)) from atmospheric pressure (kPa):\[\gamma = \frac{Cp_{air} \cdot P}{water\_vapour\_to\_dry\_air\_molecular\_weight\_ratio \cdot lambda}\]
air_specific_heat_constant_pressure is the specific heat of air at constant pressure in \(J \cdot K^{-1} \cdot kg^{-1}\). Default to 1013. It is used to compute the psychrometric constant (see equation above).
gravitational_acceleration is the gravitational acceleration in \(m \cdot s^{-2}\) and is used to compute the pressure from the elevation. Default to 9.81. See Stull (2012) and the BigLeaf R package for more details.
celsius_to_kelvin is used to convert Celsius degrees into Kelvin degrees. Default to 273.15.
universal_gas_constant defines the universal gas constant in \(J \cdot mol^{-1} \cdot K^{-1}\). Default to 8.314. It is used to compute the temperature dependence for the assimilation parameters and to convert conductance in \(mol \cdot m^{-2} \cdot s^{-1}\) into \(m \cdot s^{-1}\).
dry_air_gaz_constant is the gaz constant of dry air (Rd) in \(J \cdot kg^{-1} \cdot K^{-1}\). Default to 287.0586. It is used to compute the air density following Foken and Napo (2008):
\[R_{specific} = \frac{P}{Rd \cdot T_{air}}\]
See here for more details (Specific gas constant section).
ref_atmospheric_pressure_sea_level is the reference atmospheric pressure at sea level. It defaults to 101.325 kPa.
Stefan_Boltzmann_sigma is the Stefan-Boltzmann constant (noted \(\sigma\)). Its default value is at 5.67477e-08 \(W \cdot m^{-2} \cdot K^{-4}\). It is used to compute the emission of thermal infrared radiation (Re_TIR) by a black body:
\[Re_{TIR} = \sigma \cdot T^4\]
- sun_irradiance_to_photons is used to convert sunlight irradiance \(W \cdot m^{-2}\) into PPFD (\(\mu mol \cdot m^{-2} \cdot s^{-1}\)). It defaults to 4.57 \(\frac{\mu mol \cdot m^{-2} \cdot s^{-1}}{W \cdot m^{-2}}\)