Common_InitRad_Scalings Subroutine

public subroutine Common_InitRad_Scalings(xphi1, xphi2, xk, xvlai2, c1, rhoch, mp, nrb, Cpi180, cLAI_thresh, veg_mask, reducedLAIdue2snow, VegXfang, VegTaul, VegRefl)

Calculates the extinction coefficients for black leaves. It returns:

• the extinction coefficients for three values of the zenith angle to be used to calculate the real extinction coefficient for the diffuse radiation (Gauss quadrature)

• the $\phi$ coefficients from Sellers 1985 to calculate the real extinction coefficient for direct beam radaiation in the subroutine ExtinctionCoeff_beam

Equations

This subroutine is using the equation B6 from Wang and Leuning 1998 and equation 13 from Sellers 1985:

$$k_b = \frac{\phi_1}{\cos\theta} + \phi_2$$ $$\phi_1 = 0.5 - 0.633 \chi_L - 0.33 \chi_L^2$$ $$\phi_2 = 0.877 (1.0 - 2.0 \phi_1)$$

Arguments

Type	Intent	Optional	Attributes		Name
real,	intent(out)			::	xphi1(mp)	Leaf angle parameter defined by Sellers 1985 $\phi_1$
real,	intent(out)			::	xphi2(mp)	Leaf angle parameter defined by Sellers 1985 $\phi_2$
real,	intent(out)			::	xk(mp,nrb)	Extinction coefficients for black leaves at 3 different zenith angles
real,	intent(out)			::	xvlai2(mp,nrb)	LAI spread over the 3 different zenith angles
real,	intent(out)			::	c1(mp,nrb)
real,	intent(out)			::	rhoch(mp,nrb)
integer,	intent(in)			::	mp	Number of tiles
integer,	intent(in)			::	nrb	Number of radiation bands
real,	intent(in)			::	Cpi180	$\pi$
real,	intent(in)			::	cLAI_thresh	Threshold for the LAI under which a tile is considered unvegetated
logical,	intent(in)			::	veg_mask(mp)	Mask indicating the presence of vegetation on a tile
real,	intent(in)			::	reducedLAIdue2snow(mp)	LAI after the effect of snow
real,	intent(in)			::	VegXfang(mp)	Parameter $\chi$ in Sellers 1985
real,	intent(in)			::	VegTaul(mp,nrb)
real,	intent(in)			::	VegRefl(mp,nrb)