modules_glacier (04/19/16)

glacier

This module is defined in Classglacier and is an energy-budget firn and ice melt model loosely based on work done by  (Gray and Landine, 1987) for the Canadian Prairies. However, it has variations allowing it to input the melt input energy from other CRHM modules. The SWE is handled externally by the module "SnobalCRHM".

Use with module "pbsmCRHM". Normally uses internal melt model based upon  module "ebsm" but by using variations 1 use "Qnsn_Var (variable)", variation 2 use "Qnsn (observation)" and  with basic and variation 3 use "QnD (observation)".

Observations

• QnD (MJ/m^2 day) - net radiation. Basic module glacier and glacier#3. Always optional.
• Qnsn (W/m^2 day) - net all-wave at snow surface. Variation #2.

Variables

• firn_h (mm) - depths of snow densification layers.
• firn_dens (1000 kg/m^3) - densities of snow densification layers.
• ice_init (mm) - Initial water equivalent of glacier ice calculated from firn_h and firn_den.
• firn_yr (yr) - years to 'critical density' and age of firn.
• ice (mm) - Water equivalent of ice. State variable.
• firn (mm) - Water equivalent of all firn layers. State variable.
• glacier_all (mm) - water equivalent of SWE, firn layers and ice.
• firn_depth (mm) - depth of all firn layers.
• firn_init (mm) - initial water equivalent of all firn layers.
• nfirn () - number of layers used in firn densification.
• snow_ice_firnmeltD (mm/d) - daily snowmelt applied to SWE, firn and ice.
• cumsnow_ice_firnmelt (mm) - cummulative snowmelt applied to SWE, firn and ice.
• GlacierMode () - 1 - glacier, 0 - tongue (no firn or ice).
• SWEmelt (mm/d) - daily snowmelt.
• SWEmelt_delayed (mm/d) - daily snowmelt delayed by Clark.
• cumSWEmelt (mm) - cummulative firn snowmelt.
• firnmelt (mm/d) - daily firn melt.
• firnmelt_delayed (mm/d) - daily firn melt delayed by Clark.
• cumfirnmelt (mm) - cummulative firn melt.
• icemelt (mm/d) - daily ice melt.
• icemelt_delayed (mm/d) - daily ice melt delayed by Clark.
• cumicemelt (mm) - cummulative ice melt.
• net_rain_org (mm/int) - contents of net_rain saved before the addition of  SWE, firn and ice melt to original contents.
• LW_ebsm (mm/d) - liquid water in snowpack. State variable.
• u_ebsm (MJ/m^2*d) - snowpack energy deficit. State variable.
• Gmelt (MJ/m^2*d) - Qmelt = Qn+Qh+Qe+Qp.
• Gn_ebsm (MJ/m^2*d) - net radiation. Changed from Gn_ebsm to avoid name conflict.
• Gh_ebsm (MJ/m^2*d) - sensible heat. Changed from Qn_ebsm to avoid name conflict.
• Ge_ebsm (MJ/m^2*d) - latent heat. Changed from Qn_ebsm to avoid name conflict.
• Gp_ebsm (MJ/m^2*d) - input from rainfall. Changed from Qn_ebsm to avoid name conflict.
• SWE_2firn (mm) - end of summer SWE transferred to firn.
• SWE_2firn_dens (kg/m^3) - end of summer density of SWE transferred to firn
• cumSWE_2firn (mm) - cummulative SWE added to firn..
• LWmax (mm) -maximum liquid water in snowpack.
• net_rainD (mm/d) - daily net rain calculated from net_rain.
• Qnsn_Acc (W/m^2) - accumulator for Qnsn_Var/Qnsn. Variation  glacier#1 and #2
• topo_elev (m) - topography elevations below glacier.
• hru_elev_value (m) - topography elevations below glacier.
• snowmeltD_to_net_rain (m/d) - snowmelt/firn/ice directed to be handled like rain.
• cumsnowmeltD_to_net_rain (m) - cummulative snowmelt/firn/ice directed to be handled like rain.

Parameters

• delay_melt () - inhibits any melt before this date. Only used when tfactor and nfactor are both zero. Default value not suitable for Southern Hemisphere
• basin_area (km^2) - basin area.
• hru area (km^2) - HRU area.
• Elev_Adj_glacier_surf  () - enable add depth of glacier to land elevation (hru_elev).
• ice_init (mm) - Initial water equivalent of glacier ice.
• ice_dens (kg/m^3) - density of glacier ice.
• firn_h_init (mm) - initial depths of firn densification layers.
• firn_dens_init (1000 kg/m^3) - initial densities of firn densification layers.
• firn_Albedo () - Initial glacier firn albedo.
• ice_Albedo () - Initial glacier ice albedo.
• SWEstorage (d) - Storage constant for SWE.
• SWElag (h) - Lag constant for SWE.
• firnstorage (d) - Storage constant for firn.
• firnlag (h) - Lag constant for firn.
• icestorage (d) - Storage constant for ice.
• icelag (h) - Ice  constant for SWE.
• TKMA (ºC) - Annual mean annual temperature of glacier.
• SWEAA (mm/yy) - Annual mean accumulation of glacier SWE
• SWE_to_firn_Julian () - convert any SWE to firn on Julian day. 0 - inhibit transfer.
• Use_QnD () - Use QnD if available. Basic module.
• tfactor (mm/d*/ºC) - degree day melt factor. Basic module.
• nfactor (mm*m^2/MJ*d) - net radiation factor. Basic module.

Variable Inputs

• hru_tmean (obs) (ºC)
• hru_tmax (obs) (ºC)
• hru_tmin (obs) (ºC)
• hru_umean (obs) (m/s)
• hru_rhmean (obs) (%)
• hru_Sun_Act (obs) (hr)
• net_rain (*) (mm/int) to simplify interfacing with an infiltration routine, glacier adds SWE, firn and ice melt to net_rain. Original net_rain contents are save in net_rain_org.
• QdroD (global) (MJ/m^2)
• QdfoD (global) (MJ/m^2)
• SunMax (global) (h)
• SWE (*) (mm)
• snowmeltD (*) (mm/d)
• Qnsn_Var (W/m^2 day) - net all-wave at snow surface. Variation  glacier#1
• Pa (kPa) - atmospheric pressure.

Useage.

Qn is calculated as in the original algorithm.

Over snow during melt;

    Qn = -0.53+0.47*(QdroD+QdfoD)*(0.52+0.52*sunact/sunmax)*(1.0-Albedo)

An external observation QnD may be generated using modules long, NeedleLeaf and macro modules Slope_Qsi.mcr and Convert_Qsn_QnD.mcr.