radiationDriver.f90 File Reference

Organizes calculation of radiation-related and other surface parameters. More...

Functions/Subroutines
subroutine	radiationdriver (FC, FG, FCS, FGS, ALVSCN, ALIRCN, ALVSG, ALIRG, ALVSCS, ALIRCS, ALVSSN, ALIRSN, ALVSGC, ALIRGC, ALVSSC, ALIRSC, TRVSCN, TRIRCN, TRVSCS, TRIRCS, FSVF, FSVFS, RAICAN, RAICNS, SNOCAN, SNOCNS, FRAINC, FSNOWC, FRAICS, FSNOCS, DISP, DISPS, ZOMLNC, ZOMLCS, ZOELNC, ZOELCS, ZOMLNG, ZOMLNS, ZOELNG, ZOELNS, CHCAP, CHCAPS, CMASSC, CMASCS, CWLCAP, CWFCAP, CWLCPS, CWFCPS, RC, RCS, RBCOEF, FROOT, FROOTS, ZPLIMC, ZPLIMG, ZPLMCS, ZPLMGS, ZSNOW, WSNOW, ALVS, ALIR, HTCC, HTCS, HTC, ALTG, ALSNO, TRSNOWC, TRSNOWG, WTRC, WTRS, WTRG, CMAI, FSNOW, FCANMX, ZOLN, ALVSC, ALIRC, PAIMAX, PAIMIN, CWGTMX, ZRTMAX, RSMIN, QA50, VPDA, VPDB, PSIGA, PSIGB, PAIDAT, HGTDAT, ACVDAT, ACIDAT, ASVDAT, ASIDAT, AGVDAT, AGIDAT, ALGWV, ALGWN, ALGDV, ALGDN, THLIQ, THICE, TBAR, RCAN, SNCAN, TCAN, GROWTH, SNO, TSNOW, RHOSNO, ALBSNO, ZBLEND, Z0ORO, SNOLIM, ZPLMG0, ZPLMS0, FCLOUD, TA, VPD, RHOAIR, COSZS, FSDB, FSFB, REFSNO, BCSNO, QSWINV, RADJ, DLON, RHOSNI, DELZ, DELZW, ZBOTW, THPOR, THLMIN, PSISAT, BI, PSIWLT, HCPS, ISAND, FCANCMX, ICTEM, ctem_on, RMATC, ZOLNC, CMASVEGC, AILC, PAIC, NOL2PFTS, SLAIC, AILCG, AILCGS, FCANC, FCANCS, IDAY, ILG, IL1, IL2, NBS, JL, N, IC, ICP1, IG, IDISP, IZREF, IWF, IPAI, IHGT, IALC, IALS, IALG, ISNOALB, ALVSCTM, ALIRCTM, ipeatland)

Detailed Description

Organizes calculation of radiation-related and other surface parameters.

Author

D. Verseghy, M. Lazare, J. Cole, Y. Wu, J. Melton

Function/Subroutine Documentation

radiationdriver()

subroutine radiationdriver	(	real, dimension (ilg), intent(out)	FC,
		real, dimension (ilg), intent(out)	FG,
		real, dimension (ilg), intent(out)	FCS,
		real, dimension (ilg), intent(out)	FGS,
		real, dimension(ilg), intent(out)	ALVSCN,
		real, dimension(ilg), intent(out)	ALIRCN,
		real, dimension (ilg), intent(out)	ALVSG,
		real, dimension (ilg), intent(out)	ALIRG,
		real, dimension(ilg), intent(out)	ALVSCS,
		real, dimension(ilg), intent(out)	ALIRCS,
		real, dimension(ilg), intent(out)	ALVSSN,
		real, dimension(ilg), intent(out)	ALIRSN,
		real, dimension(ilg), intent(out)	ALVSGC,
		real, dimension(ilg), intent(out)	ALIRGC,
		real, dimension(ilg), intent(out)	ALVSSC,
		real, dimension(ilg), intent(out)	ALIRSC,
		real, dimension(ilg), intent(out)	TRVSCN,
		real, dimension(ilg), intent(out)	TRIRCN,
		real, dimension(ilg), intent(out)	TRVSCS,
		real, dimension(ilg), intent(out)	TRIRCS,
		real, dimension (ilg), intent(out)	FSVF,
		real, dimension (ilg), intent(out)	FSVFS,
		real, dimension(ilg), intent(out)	RAICAN,
		real, dimension(ilg), intent(out)	RAICNS,
		real, dimension(ilg), intent(out)	SNOCAN,
		real, dimension(ilg), intent(out)	SNOCNS,
		real, dimension(ilg), intent(out)	FRAINC,
		real, dimension(ilg), intent(out)	FSNOWC,
		real, dimension(ilg), intent(out)	FRAICS,
		real, dimension(ilg), intent(out)	FSNOCS,
		real, dimension (ilg), intent(out)	DISP,
		real, dimension (ilg), intent(out)	DISPS,
		real, dimension(ilg), intent(out)	ZOMLNC,
		real, dimension(ilg), intent(out)	ZOMLCS,
		real, dimension(ilg), intent(out)	ZOELNC,
		real, dimension(ilg), intent(out)	ZOELCS,
		real, dimension(ilg), intent(out)	ZOMLNG,
		real, dimension(ilg), intent(out)	ZOMLNS,
		real, dimension(ilg), intent(out)	ZOELNG,
		real, dimension(ilg), intent(out)	ZOELNS,
		real, dimension (ilg), intent(out)	CHCAP,
		real, dimension(ilg), intent(out)	CHCAPS,
		real, dimension(ilg), intent(out)	CMASSC,
		real, dimension(ilg), intent(out)	CMASCS,
		real, dimension(ilg), intent(out)	CWLCAP,
		real, dimension(ilg), intent(out)	CWFCAP,
		real, dimension(ilg), intent(out)	CWLCPS,
		real, dimension(ilg), intent(out)	CWFCPS,
		real, dimension (ilg), intent(out)	RC,
		real, dimension (ilg), intent(out)	RCS,
		real, dimension(ilg), intent(out)	RBCOEF,
		real, dimension (ilg,ig), intent(out)	FROOT,
		real, dimension(ilg,ig), intent(out)	FROOTS,
		real, dimension(ilg), intent(out)	ZPLIMC,
		real, dimension(ilg), intent(out)	ZPLIMG,
		real, dimension(ilg), intent(out)	ZPLMCS,
		real, dimension(ilg), intent(out)	ZPLMGS,
		real, dimension (ilg), intent(out)	ZSNOW,
		real, dimension (ilg), intent(out)	WSNOW,
		real, dimension (ilg), intent(out)	ALVS,
		real, dimension (ilg), intent(out)	ALIR,
		real, dimension (ilg), intent(out)	HTCC,
		real, dimension (ilg), intent(out)	HTCS,
		real, dimension (ilg,ig), intent(out)	HTC,
		real, dimension(ilg,nbs), intent(out)	ALTG,
		real, dimension(ilg,nbs), intent(out)	ALSNO,
		real, dimension(ilg), intent(out)	TRSNOWC,
		real, dimension(ilg,nbs), intent(out)	TRSNOWG,
		real, dimension (ilg), intent(out)	WTRC,
		real, dimension (ilg), intent(out)	WTRS,
		real, dimension (ilg), intent(out)	WTRG,
		real, dimension (ilg), intent(out)	CMAI,
		real, dimension (ilg), intent(out)	FSNOW,
		real, dimension(ilg,icp1), intent(in)	FCANMX,
		real, dimension (ilg,icp1), intent(in)	ZOLN,
		real, dimension (ilg,icp1), intent(inout)	ALVSC,
		real, dimension (ilg,icp1), intent(inout)	ALIRC,
		real, dimension(ilg,ic), intent(in)	PAIMAX,
		real, dimension(ilg,ic), intent(in)	PAIMIN,
		real, dimension(ilg,ic), intent(in)	CWGTMX,
		real, dimension(ilg,ic), intent(in)	ZRTMAX,
		real, dimension (ilg,ic), intent(in)	RSMIN,
		real, dimension (ilg,ic), intent(in)	QA50,
		real, dimension (ilg,ic), intent(in)	VPDA,
		real, dimension (ilg,ic), intent(in)	VPDB,
		real, dimension (ilg,ic), intent(in)	PSIGA,
		real, dimension (ilg,ic), intent(in)	PSIGB,
		real, dimension(ilg,ic), intent(in)	PAIDAT,
		real, dimension(ilg,ic), intent(in)	HGTDAT,
		real, dimension(ilg,ic), intent(in)	ACVDAT,
		real, dimension(ilg,ic), intent(in)	ACIDAT,
		real, dimension(ilg), intent(in)	ASVDAT,
		real, dimension(ilg), intent(in)	ASIDAT,
		real, dimension(ilg), intent(in)	AGVDAT,
		real, dimension(ilg), intent(in)	AGIDAT,
		real, dimension(ilg), intent(in)	ALGWV,
		real, dimension(ilg), intent(in)	ALGWN,
		real, dimension(ilg), intent(in)	ALGDV,
		real, dimension(ilg), intent(in)	ALGDN,
		real, dimension (ilg,ig), intent(in)	THLIQ,
		real, dimension (ilg,ig), intent(in)	THICE,
		real, dimension (ilg,ig), intent(in)	TBAR,
		real, dimension (ilg), intent(in)	RCAN,
		real, dimension (ilg), intent(in)	SNCAN,
		real, dimension (ilg), intent(in)	TCAN,
		real, dimension(ilg), intent(in)	GROWTH,
		real, dimension (ilg), intent(in)	SNO,
		real, dimension (ilg), intent(in)	TSNOW,
		real, dimension(ilg), intent(in)	RHOSNO,
		real, dimension(ilg), intent(in)	ALBSNO,
		real, dimension(ilg), intent(in)	ZBLEND,
		real, dimension (ilg), intent(in)	Z0ORO,
		real, dimension(ilg), intent(in)	SNOLIM,
		real, dimension(ilg), intent(in)	ZPLMG0,
		real, dimension(ilg), intent(in)	ZPLMS0,
		real, dimension(ilg), intent(in)	FCLOUD,
		real, dimension (ilg), intent(in)	TA,
		real, dimension (ilg), intent(in)	VPD,
		real, dimension(ilg), intent(in)	RHOAIR,
		real, dimension (ilg), intent(in)	COSZS,
		real, dimension(ilg,nbs), intent(in)	FSDB,
		real, dimension(ilg,nbs), intent(in)	FSFB,
		real, dimension(ilg), intent(in)	REFSNO,
		real, dimension(ilg), intent(in)	BCSNO,
		real, dimension(ilg), intent(in)	QSWINV,
		real, dimension (ilg), intent(in)	RADJ,
		real, dimension (ilg), intent(in)	DLON,
		real, dimension(ilg), intent(in)	RHOSNI,
		real, dimension (ig), intent(in)	DELZ,
		real, dimension (ilg,ig), intent(in)	DELZW,
		real, dimension (ilg,ig), intent(in)	ZBOTW,
		real, dimension (ilg,ig), intent(in)	THPOR,
		real, dimension(ilg,ig), intent(in)	THLMIN,
		real, dimension(ilg,ig), intent(in)	PSISAT,
		real, dimension (ilg,ig), intent(in)	BI,
		real, dimension(ilg,ig), intent(in)	PSIWLT,
		real, dimension (ilg,ig), intent(in)	HCPS,
		integer, dimension (ilg,ig), intent(in)	ISAND,
		real, dimension(ilg,ictem), intent(in)	FCANCMX,
		integer, intent(in)	ICTEM,
		logical, intent(in)	ctem_on,
		real, dimension(ilg,ic,ig), intent(in)	RMATC,
		real, dimension(ilg,ic), intent(in)	ZOLNC,
		real, dimension(ilg,ic), intent(in)	CMASVEGC,
		real, dimension(ilg,ic), intent(in)	AILC,
		real, dimension(ilg,ic), intent(in)	PAIC,
		integer, dimension(ic), intent(in)	NOL2PFTS,
		real, dimension(ilg,ic), intent(in)	SLAIC,
		real, dimension(ilg,ictem), intent(in)	AILCG,
		real, dimension(ilg,ictem), intent(in)	AILCGS,
		real, dimension(ilg,ictem), intent(in)	FCANC,
		real, dimension(ilg,ictem), intent(in)	FCANCS,
		integer, intent(in)	IDAY,
		integer, intent(in)	ILG,
		integer, intent(in)	IL1,
		integer, intent(in)	IL2,
		integer, intent(in)	NBS,
		integer, intent(in)	JL,
		integer, intent(in)	N,
		integer, intent(in)	IC,
		integer, intent(in)	ICP1,
		integer, intent(in)	IG,
		integer, intent(in)	IDISP,
		integer, intent(in)	IZREF,
		integer, intent(in)	IWF,
		integer, intent(in)	IPAI,
		integer, intent(in)	IHGT,
		integer, intent(in)	IALC,
		integer, intent(in)	IALS,
		integer, intent(in)	IALG,
		integer, intent(in)	ISNOALB,
		real, dimension(ilg,ic), intent(in)	ALVSCTM,
		real, dimension(ilg,ic), intent(in)	ALIRCTM,
		integer, dimension(ilg), intent(in)	ipeatland
	)

Parameters

[in]	isnoalb	Switch to model snow albedo in two or more wavelength bands
[out]	fc	Subarea fractional coverage of modelled area [ ]
[out]	fg	Subarea fractional coverage of modelled area [ ]
[out]	fcs	Subarea fractional coverage of modelled area [ ]
[out]	fgs	Subarea fractional coverage of modelled area [ ]
[out]	alvscn	Visible albedo of vegetation over bare ground [ ]
[out]	alircn	Near-IR albedo of vegetation over bare ground [ ]
[out]	alvsg	Visible albedo of open bare ground [ ]
[out]	alirg	Near-IR albedo of open bare ground [ ]
[out]	alvscs	Visible albedo of vegetation over snow [ ]
[out]	alircs	Near-IR albedo of vegetation over snow [ ]
[out]	alvssn	Visible albedo of open snow cover [ ]
[out]	alirsn	Near-IR albedo of open snow cover [ ]
[out]	alvsgc	Visible albedo of bare ground under vegetation [ ]
[out]	alirgc	Near-IR albedo of bare ground under vegetation [ ]
[out]	alvssc	Visible albedo of snow under vegetation [ ]
[out]	alirsc	Near-IR albedo of snow under vegetation [ ]
[out]	trvscn	Visible transmissivity of vegetation over bare ground [ ]
[out]	trircn	Near-IR transmissivity of vegetation over bare ground [ ]
[out]	trvscs	Visible transmissivity of vegetation over snow [ ]
[out]	trircs	Near-IR transmissivity of vegetation over snow [ ]
[out]	fsvf	Sky view factor for bare ground under canopy [ ]
[out]	fsvfs	Sky view factor for snow under canopy [ ]
[out]	raican	Intercepted liquid water stored on canopy over bare ground \([kg m^{-2}]\)
[out]	raicns	Intercepted liquid water stored on canopy over snow \([kg m^{-2}]\)
[out]	snocan	Intercepted frozen water stored on canopy over bare soil \([kg m^{-2}]\)
[out]	snocns	Intercepted frozen water stored on canopy over snow \([kg m^{-2}]\)
[out]	frainc	Fractional coverage of canopy by liquid water over snow-free subarea [ ]
[out]	fsnowc	Fractional coverage of canopy by frozen water over snow-free subarea [ ]
[out]	fraics	Fractional coverage of canopy by liquid water over snow-covered subarea [ ]
[out]	fsnocs	Fractional coverage of canopy by frozen water over snow-covered subarea [ ]
[out]	disp	Displacement height of vegetation over bare ground [m]
[out]	disps	Displacement height of vegetation over snow [m]
[out]	zomlnc	Logarithm of roughness length for momentum of vegetation over bare ground [ ]
[out]	zomlcs	Logarithm of roughness length for momentum of vegetation over snow [ ]
[out]	zoelnc	Logarithm of roughness length for heat of vegetation over bare ground [ ]
[out]	zoelcs	Logarithm of roughness length for heat of vegetation over snow [ ]
[out]	zomlng	Logarithm of roughness length for momentum of bare ground [ ]
[out]	zomlns	Logarithm of roughness length for momentum of snow [ ]
[out]	zoelng	Logarithm of roughness length for heat of bare ground [ ]
[out]	zoelns	Logarithm of roughness length for heat of snow [ ]
[out]	chcap	Heat capacity of canopy over bare ground \( [J m^{-2} K^{-1}]\)
[out]	chcaps	Heat capacity of canopy over snow \([J m^{-2} K^{-1}]\)
[out]	cmassc	Mass of canopy over bare ground \([kg m^{-2}]\)
[out]	cmascs	Mass of canopy over snow \([kg m^{-2}]\)
[out]	cwlcap	Storage capacity of canopy over bare ground for liquid water \([kg m^{-2}]\)
[out]	cwfcap	Storage capacity of canopy over bare ground for frozen water \([kg m^{-2}]\)
[out]	cwlcps	Storage capacity of canopy over snow for liquid water \([kg m^{-2}]\)
[out]	cwfcps	Storage capacity of canopy over snow for frozen water \([kg m^{-2}]\)
[out]	rc	Stomatal resistance of vegetation over bare ground \([s m^{-1}]\)
[out]	rcs	Stomatal resistance of vegetation over snow \([s m^{-1}]\)
[out]	zplimc	Maximum water ponding depth for ground under canopy [m]
[out]	zplimg	Maximum water ponding depth for bare ground [m]
[out]	zplmcs	Maximum water ponding depth for ground under snow under canopy [m]
[out]	zplmgs	Maximum water ponding depth for ground under snow [m]
[out]	rbcoef	Parameter for calculation of leaf boundary resistance
[out]	trsnowc	Short-wave transmissivity of snow pack under vegetation [ ]
[out]	zsnow	Depth of snow pack \([m] (z_s)\)
[out]	wsnow	Liquid water content of snow pack \([kg m^{-2}]\)
[out]	alvs	Diagnosed total visible albedo of land surface [ ]
[out]	alir	Diagnosed total near-infrared albedo of land surface [ ]
[out]	htcc	Diagnosed internal energy change of vegetation canopy due to conduction and/or change in mass \([W m^{-2}]\)
[out]	htcs	Diagnosed internal energy change of snow pack due to conduction and/or change in mass \([W m^{-2}]\)
[out]	wtrc	Diagnosed residual water transferred off the vegetation canopy \([kg m^{-2} s^{-1}]\)
[out]	wtrs	Diagnosed residual water transferred into or out of the snow pack \([kg m^{-2} s^{-1}]\)
[out]	wtrg	Diagnosed residual water transferred into or out of the soil \([kg m^{-2} s^{-1}]\)
[out]	cmai	Aggregated mass of vegetation canopy \([kg m^{-2}]\)
[out]	fsnow	Diagnosed fractional snow coverage [ ]
[out]	froot	Fraction of total transpiration contributed by soil layer over snow-free subarea [ ]
[out]	froots	Fraction of total transpiration contributed by snow-covered subarea [ ]
[out]	htc	Diagnosed internal energy change of soil layer due to conduction and/or change in mass \([W m^{-2}]\)
[out]	trsnowg	Short-wave transmissivity of snow pack in bare areas [ ]
[out]	altg	Total albedo in each modelled wavelength band [ ]
[out]	alsno	Albedo of snow in each modelled wavelength band [ ]
[in]	fcanmx	Maximum fractional coverage of modelled area by vegetation category [ ]
[in]	zoln	Natural logarithm of maximum roughness length of vegetation category [ ]
[in,out]	alvsc	Background average visible albedo of vegetation category [ ]
[in,out]	alirc	Background average near-infrared albedo of vegetation category [ ]
[in]	paimax	Maximum plant area index of vegetation category [ ]
[in]	paimin	Minimum plant area index of vegetation category [ ]
[in]	cwgtmx	Maximum canopy mass for vegetation category \([kg m^{-2}]\)
[in]	zrtmax	Maximum rooting depth of vegetation category [m]
[in]	rsmin	Minimum stomatal resistance of vegetation category \([s m^{-1}]\)
[in]	qa50	Reference value of incoming shortwave radiation for vegetation category (used in stomatal resistance calculation) \([W m^{-2}]\)
[in]	vpda	Vapour pressure deficit coefficient for vegetation category (used in stomatal resistance calculation) [ ]
[in]	vpdb	Vapour pressure deficit coefficient for vegetation category (used in stomatal resistance calculation) [ ]
[in]	psiga	Soil moisture suction coefficient for vegetation category (used in stomatal resistance calculation) [ ]
[in]	psigb	Soil moisture suction coefficient for vegetation category (used in stomatal resistance calculation) [ ]
[in]	paidat	Optional user-specified value of plant area indices of vegetation categories to override CLASS-calculated values [ ]
[in]	hgtdat	Optional user-specified values of height of vegetation categories to override CLASS- calculated values [m]
[in]	acvdat	Optional user-specified value of canopy visible albedo to override CLASS-calculated value [ ]
[in]	acidat	Optional user-specified value of canopy near-infrared albedo to override CLASS- calculated value [ ]
[in]	thliq	Volumetric liquid water content of soil layers \([m^3 m^{-3}]\)
[in]	thice	Volumetric frozen water content of soil layers \([m^3 m^{-3}]\)
[in]	tbar	Temperature of soil layers [K]
[in]	asvdat	Optional user-specified value of snow visible albedo to override CLASS-calculated value [ ]
[in]	asidat	Optional user-specified value of snow near- infrared albedo to override CLASS-calculated value [ ]
[in]	agvdat	Optional user-specified value of ground visible albedo to override CLASS-calculated value [ ]
[in]	agidat	Optional user-specified value of ground near- infrared albedo to override CLASS-calculated value [ ]
[in]	algwv	Reference albedo for saturated soil (visible) [ ]
[in]	algwn	Reference albedo for saturated soil (NIR) [ ]
[in]	algdv	Reference albedo for dry soil (visible) [ ]
[in]	algdn	Reference albedo for dry soil (NIR) [ ]
[in]	rhosni	Density of fresh snow \([kg m^{-3}]\)
[in]	z0oro	Orographic roughness length [m]
[in]	rcan	Intercepted liquid water stored on canopy \([kg m^{-2}]\)
[in]	sncan	Intercepted frozen water stored on canopy \([kg m^{-2}]\)
[in]	tcan	Vegetation canopy temperature [K]
[in]	growth	Vegetation growth index [ ]
[in]	sno	Mass of snow pack \([kg m^{-2}] (W_s)\)
[in]	tsnow	Snowpack temperature [K]
[in]	rhosno	Density of snow \([kg m^{-3}] (\rho_s)\)
[in]	albsno	Snow albedo [ ]
[in]	fcloud	Fractional cloud cover [ ]
[in]	ta	Air temperature at reference height [K]
[in]	vpd	Vapour pressure deficit of air [mb]
[in]	rhoair	Density of air \([kg m^{-3}]\)
[in]	coszs	Cosine of solar zenith angle [ ]
[in]	qswinv	Visible radiation incident on horizontal surface \([W m^{-2}]\)
[in]	dlon	Longitude of grid cell (east of Greenwich) [degrees]
[in]	zblend	Atmospheric blending height for surface roughness length averaging [m]
[in]	snolim	Limiting snow depth below which coverage is < 100% \([m] (z_{s,lim})\)
[in]	zplmg0	Maximum water ponding depth for snow-free subareas (user-specified when running MESH code) [m]
[in]	zplms0	Maximum water ponding depth for snow-covered subareas (user-specified when running MESH code) [m]
[in]	radj	Latitude of grid cell (positive north of equator) [rad]
[in]	refsno	Snow grain size (for ISNOALB=1 option) [m]
[in]	bcsno	Black carbon mixing ratio (for ISNOALB=1 option) \([kg m^{-3}]\)
[in]	fsdb	Direct solar radiation in each modelled wavelength band \([W m^{-2}]\)
[in]	fsfb	Diffuse solar radiation in each modelled wavelength band \([W m^{-2}]\)
[in]	delzw	Permeable thickness of soil layer [m]
[in]	delz	Soil layer thickness [m]
[in]	zbotw	Depth to permeable bottom of soil layer [m]
[in]	thpor	Pore volume in soil layer \([m^3 m^{-3}]\)
[in]	thlmin	Residual soil liquid water content remaining after freezing or evaporation \([m^3 m^{-3}]\)
[in]	psisat	Soil moisture suction at saturation [m]
[in]	bi	Clapp and Hornberger empirical "b" parameter [ ]
[in]	psiwlt	Soil moisture suction at wilting point [m]
[in]	hcps	Volumetric heat capacity of soil particles \([J m^{-3}]\)
[in]	isand	Sand content flag
[in]	ipeatland	Peatland flag: 0 = not a peatland, 1 = bog, 2 = fen

In the first loop, the depth of snow \(z_s\) is calculated from the snow mass \(W_s\) and density \(\varrho_s\) as: \( z_s = W_s / \varrho_s. \)

If the calculated value of \(z_s\) is less than the limiting snow depth \(z_{s, lim}\), the snow cover is deemed to be discontinuous. The fractional snow coverage \(X_s\) of the modelled area is evaluated as \( X_s = z_s / z_{s, lim} \) and the snow depth is reset to \(z_{s, lim}\). The water content of the snow pack is corrected according to the new snow fractional area.

The subarea albedo and transmissivity arrays (for canopy, bare ground, canopy over snow and snow over bare ground) are next initialized to zero, and the four radiationDriver subsidiary subroutines are called in turn: calcLandSurfParams to evaluate various model parameters for the four subareas, groundAlbedo to calculate the ground surface albedo, snowAlbedoTransmiss to calculate the snow albedo and transmissivity, and canopyAlbedoTransmiss to calculate the canopy albedo, transmissivity and stomatal resistance. Finally, the overall visible, near-infrared and total albedos for the modelled area are determined as weighted averages over the four subareas.