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net.simplace.usermodules.ET_Study.CropEvapoTranspirationDualCoeff

Calculates the basal crop coefficient and the soil evaporation coefficient, as well as potential crop transpiration and potential soil evaporation using formulas from (FAO 56).

For calculations following daily inputs are needed

ET0 reference crop evapotranspiration
LAI leaf area index
DVS development stage of the plant
K_r evaporation reduction factor due to depletion of the upper soil layer
K_s transpiration reduction factor due to water stress

When K_r is not available, then a value of 1 is used. In this case one might use the outputs KeUpper, PotentialSoilEvaporationUpper and ETCUpper instead of Ke, PotentialSoilEvaporation and ETC. (??? - if no K_r given, what should be used: Ke with K_r=1 or KeUpper?)

If development stage is less than 0.001, then Kcb is set to the initial value KcbIni. Otherwise Kcb is set to KcbMidLAI, which is calculated according to (FAO 56). (??? - is there any reference for this proceeding)

For full documentation of the formulas please check the orginal reference (FAO 56)

References: Allen et al., 1996. Crop evapotranspiration - Guidelines for computing crop water requirements - FAO Irrigation and drainage paper 56, 1998 http://www.fao.org/docrep/x0490e/x0490e00.htm

Component Variables

Content Type	Name	Description	Data Type	Unit	Min Value	Max Value	Default Value
constant	cCharacteristicMeanRelHumidity	region's characteristic mean daily min relative humidity for mid/late growth season	DOUBLE	%	0.0	100.0	45.0
constant	cCharacteristicWindSpeed	region's characteristic wind speed at 2m during the mid growing season m s-1	DOUBLE	m/s	0.0	-	2.0
constant	cCropHeight	average crop height during mid/late season	DOUBLE	m	0.0	5.0	0.0
constant	cKcMin	min Kc for dry bare soil with no ground cover	DOUBLE	1	0.0	2.0	0.15
constant	cKcbIni	nominal Kcb value during initial growth stage	DOUBLE	1	0.0	2.0	0.0
constant	cKcbMid	nominal peak Kcb value obtained during mid season growth stage	DOUBLE	1	0.0	2.0	0.0
constant	cWettedSoilFraction	fraction of soil surface wetted by rain or irrigation	DOUBLE	1	0.0	1.0	1.0
constant	iK_r	Evaporation reduction coefficient (optional, if null no ActualSoilEvapCrop is calculated)	DOUBLE	1	0.0	1.0	-
constant	if_c	Covered soil fraction (optional - normally calculated from crop height)	DOUBLE	1	0.0	1.0	-
input	iDVS	daily value of development stage	DOUBLE	1	0.0	2.5	0.0
input	iDoHarvest	harvesting	BOOLEAN	1	-	-	false
input	iDoSow	sowing	BOOLEAN	1	-	-	false
input	iET0	reference crop evapotranspiration	DOUBLE	mm	0.0	20.0	0.0
input	iLAI	daily estimated leaf area index	DOUBLE	1	0.0	20.0	0.0
ActualSoilEvapCrop	Actual rate of evaporation from the soil	DOUBLE	mm/d	null
ETC	Crop ET under standard conditions if K_r is supplied (no water, nutrient, weed, pest or disease limitations to growth)	DOUBLE	mm/d	null
ETCUpper	Upper limit (no evaporation reduction K_r) of crop ET under standard (or - when K_s is set - water stress) conditions (no nutrient, weed, pest or disease limitations to growth)	DOUBLE	mm/d	null
Kcb	Basal crop coefficient	DOUBLE	1	null
Ke	Soil evaporation coefficient	DOUBLE	1	null
KeUpper	Upper limit of soil evaporation coefficient (no evaporation reduction K_r)	DOUBLE	1	null
PotentialSoilEvapCrop	Potential rate of evaporation from the soil	DOUBLE	mm/d	null
PotentialTranCrop	Potential rate of transpiration from the crop	DOUBLE	mm/d	null

public class CropEvapoTranspirationDualCoeff extends
net.simplace.simulation.model.FWSimComponent {
// Public Constructors
public CropEvapoTranspirationDualCoeff();

// Public Instance Methods

public HashMap createVariables(); // Defines
net.simplace.simulation.model.FWSimComponent

Create the FWSimVariables as interface for this SimComponent

// Protected Instance Methods

protected void init(); // Defines
net.simplace.simulation.model.FWSimComponent

Initialises the fields by getting input and output FWSimVariables from VarMap

protected void initValues();

protected void resetOnHarvest();

protected void process(); // Defines
net.simplace.simulation.model.FWSimComponent

Process the algorithm and write the results back to VarMap

protected void PotTran();

Calculates K_cb and potential transpiration of crop

protected void SoilEvap();

Calculates K_e and potential soil evaporation

protected FWSimComponent clone(FWSimVarMap aVarMap);
// Defines net.simplace.simulation.model.FWSimComponent

creates a clone from this SimComponent for use in other threads

}

Hierarchy: java.lang.Object - net.simplace.simulation.model.FWSimComponent (net.simplace.simulation.util.FWSimFieldContainer) - CropEvapoTranspirationDualCoeff