Canopy Class Reference

Detailed Description

Computes interception of precipitation and radiation, and reduction of windspeed in a canopy layer above thesnow or soil surface. This has been published in Gouttevin, I., M. Lehning, T. Jonas, D. Gustafsson, and Meelis Mölder, "A two-layer canopy model with thermal inertia for an improved snowpack energy balance below needleleaf forest (model SNOWPACK, version 3.2. 1, revision 741).", Geoscientific Model Development 8.8, pp 2379-2398, 2015.

Canopy modeling

1. 2layer canopy model:
   • key: TWO_LAYER_CANOPY = true [Snowpack]
   • logical in the code: Twolayercanopy
   • content: canopy is divided into a trunk layer (interception radiations with factor sigftrunk) and a leaf-layer (intercepting radiations with factor sigf). SW radiations reaching the ground are modified accordingly. An energy balance is computed for each layer, producing leaf-layer and trunk layer temperatures (TC and Ttrunk) that affect LW radiations to the ground. Optionally, trunks can get direct solar insolation (important for sparse canopies), look for CanClosDirTrunks in the code
   • further details: Gouttevin et al. (2014): A two-layer canopy with thermal inertia for an improved modelling of the sub-canopy snowpack energy-balance (in prep).
2. canopy heat mass:
   • key: CANOPY_HEAT_MASS = true [Snowpack]
   • logical in the code: CanopyHeatMass
   • content: the canopy gets an heat mass (whole, or separate between trunks and leaves if Twolayercanopy) that adds a biomass heat flux term in the canopy energy balance.
   • an additionnal parameter is now required in the input/station.snoold file : CanopyBasalArea (m2/m2), to be placed after CanopyLeafAreaIndex. Example value for closed canopies like Alptal : 0.004.
   • further details: Gouttevin et al. (2014): A two-layer canopy with thermal inertia for an improved modelling of the sub-canopy snowpack energy-balance (in prep).
3. forest-floor albedo:
   • key: FORESTFLOOR_ALB = true [Snowpack]
   • logical in the code: forestfloor_alb
   • content: Litter falling on the forest floor can reduce albedo. This effect is currently parameterized through an exponential decay of the albedo to a value of 0.3 with a time-constant of 7 days, based on parameterizations commonly used in Land-Surface models. There is room for improvement !

Important comments:

• Snowpack can take precipitation phase (relying on the psum_ph variable) for applications such as the SnowMIP experiments (Rutter et al., 2009).
• an additionnal parameter is now required in the input/station.snoold file : CanopyBasalArea (m2/m2), to be placed after CanopyLeafAreaIndex.
• Some cleaning was done to suppressed outputs that can be easily derived from other outputs. There is now space for outputs specific to the 2layer model, which are written if variant = 2L_CANOPY in [SnowpackAdvanced] (Canopy::writeTimeSeriesAdd2LCanopy).

#include <Canopy.h>

Public Member Functions
	Canopy (const SnowpackConfig &i_cfg)
bool	runCanopyModel (CurrentMeteo &Mdata, SnowStation &Xdata, const double &roughness_length, const double &height_of_wind_val, const bool &adjust_VW_height=true)
	MAIN CANOPY FUNCTION CALLED BY Meteo.c This routine computes interception of precipitation and radiation, and reduction of turbulent exchange in a canopy layer above the ground. Computations are made in the following order: More...

Static Public Member Functions
static void	DumpCanopyHeader (std::ofstream &fout)
	Write header for 28 canopy parameters to Outfile, columns 65-92. More...
static void	DumpCanopyUnits (std::ofstream &fout)
	Write units for 28 canopy parameters to Outfile, columns 65-92. More...
static void	DumpCanopyData (std::ofstream &fout, const CanopyData *Cdata, const SurfaceFluxes *Sdata, const double cos_sl)
	Dump 28 canopy parameters to Outfile, columns 65-92. More...
static void	writeTimeSeriesAdd2LCanopy (std::ofstream &fout, const CanopyData *Cdata)

Constructor & Destructor Documentation

Canopy()

Canopy::Canopy

(

const SnowpackConfig &

i_cfg

)

Member Function Documentation

DumpCanopyData()

void Canopy::DumpCanopyData ( std::ofstream &  fout, const CanopyData *  Cdata, const SurfaceFluxes *  Sdata, const double  cos_sl  )

static

Dump 28 canopy parameters to Outfile, columns 65-92.

Parameters

fout	Dump file stream
*Cdata
*Sdata
cos_sl	Cosine of slope angle

DumpCanopyHeader()

void Canopy::DumpCanopyHeader ( std::ofstream &  fout )

static

Write header for 28 canopy parameters to Outfile, columns 65-92.

Parameters

fout	Dump file stream

DumpCanopyUnits()

void Canopy::DumpCanopyUnits ( std::ofstream &  fout )

static

Write units for 28 canopy parameters to Outfile, columns 65-92.

Parameters

fout	Dump file stream

runCanopyModel()

bool Canopy::runCanopyModel	(	CurrentMeteo &	Mdata,
		SnowStation &	Xdata,
		const double &	roughness_length,
		const double &	height_of_wind_val,
		const bool &	adjust_VW_height = true
	)

MAIN CANOPY FUNCTION CALLED BY Meteo.c This routine computes interception of precipitation and radiation, and reduction of turbulent exchange in a canopy layer above the ground. Computations are made in the following order:

1. Preliminar mass balance (interception and throughfall)
2. Canopy surface energy balance (net radiation, sensible and latent heat fluxes)
3. Final mass balance (evaporation of intercepted water, and transpiration

   Parameters

   Mdata	CurrentMeteo
   Xdata	Profile
   roughness_length
   height_of_wind_val
   adjust_VW_height	if set to false, assumes a constant measurement height for wind values (default: true, ie. take into account the snow height decreasing the sensor height above the surface)

   Returns

   true if the canopy module could be used, false if not (canopy under the snow, etc)

writeTimeSeriesAdd2LCanopy()

void Canopy::writeTimeSeriesAdd2LCanopy ( std::ofstream &  fout, const CanopyData *  Cdata  )

static

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The documentation for this class was generated from the following files:

• Canopy.h
• Canopy.cc