Detailed Description

Calculates the Evapotranspiration using Hargreave's equation.

\[ET_{rc} = 0.0135 K_T\ s_0 \sqrt{\Delta T} (T + 17.8)\]

where:

\( ET_{rc} \) the reference crop evapotranspiration in mm/day
\( K_T = 0.00185 {\Delta T}^2 - 0.0433 \Delta T + 0.4023\) Continentality factor as given in the reference
\( \Delta T = |T_{max} - T_{min}|[K]\) Daily temperature range
\( T [^\circ C]\) daily mean temperature
\( s_0 = 15.392 d_r \left(\omega_s\sin(\Phi) \sin{\gamma} + \cos{\Phi}\cos{\gamma} * \sin(\omega_s)\right)\) the extraterrestrial solar radiation in mm/day
\( d_r = 1 + 0.0033 \cos(DOY\frac{2 \pi}{365})\) relative distance between earth and sun
\( \omega_s = \arccos(-\tan{\Phi} \tan{\gamma}) \) sunset hour angle (radians)
\( \gamma = 0.4039 \sin(DOY\frac{2 \pi}{365} - 1.405) \) solar declination (radians)
\( \Phi\) geographic latitude (radians)

See also: SAMANI, Zohrab. Estimating solar radiation and evapotranspiration using minimum climatological data. Journal of Irrigation and Drainage Engineering, 2000, 126. Jg., Nr. 4, S. 265-267.

Crop specific potential evapotranspiration is scaled by LAI: \( ET_{pot} = ET_{rc} \frac{LAI}{2.88}\).

Public Member Functions
real	conc (cmf::math::Time t, const cmf::water::solute &_Solute)
	Returns the concentration of the flux.

flux_node::ptr	get_target (const flux_node &inquirer)
	Returns the other end of a connection than the asking end.

flux_node::ptr	get_target (int index) const
	With index 0, the left node is returned, with index 1 the right node of the connection.

real	get_tracer_filter ()
	A value ranging from 0 to 1 to filter tracers out of the water flux.

real	get_tracer_filter (solute S)
	A value ranging from 0 to 1 to filter tracers out of the water flux.

bool	kill_me ()
	Deregisters this connection from its nodes. Returns true if only one reference is left.

flux_node::ptr	left_node () const
	Returns the left node of this connection.

real	q (const flux_node &inquirer, cmf::math::Time t)
	Returns the current flux through a connection. Negative signs mean out of the inquirer, positive are inflows to the inquirer.

void	refresh (cmf::math::Time t)
	Performes a new calculation of the flux.

flux_node::ptr	right_node () const
	returns the right node of this connection

void	set_tracer_filter (real value)
	A value ranging from 0 to 1 to filter tracers out of the water flux.

Static Public Member Functions
static void	use_for_cell (cmf::upslope::Cell &cell)
	Connects all soil layers with the transpiration node of the cell.

Public Attributes
const std::string	type
	A string describing the type of the connection.

Member Function Documentation

real conc	(	cmf::math::Time	t,
		const cmf::water::solute &	_Solute )

inherited

Returns the concentration of the flux.

If not overridden, it returns the concentration of the source of the flux (direction depending)

real get_tracer_filter ( )

inherited

A value ranging from 0 to 1 to filter tracers out of the water flux.

1.0 is no filter and 0.0 means no solute is crossing this connection

void set_tracer_filter ( real value )

inherited

A value ranging from 0 to 1 to filter tracers out of the water flux.

1.0 is no filter and 0.0 means no solute is crossing this connection