GFS sfc_sice Module

This is three-layer thermodynomics sea-ice model based on Winton (2000) [197]. More...

Functions/Subroutines
subroutine	sfc_sice::sfc_sice_run (im, kice, sbc, hvap, tgice, cp, eps, epsm1, rvrdm1, grav, t0c, rd, ps, t1, q1, delt, sfcemis, dlwflx, sfcnsw, sfcdsw, srflag, cm, ch, prsl1, prslki, prsik1, prslk1, wind, flag_iter, use_lake_model, lprnt, ipr, thsfc_loc, hice, fice, tice, weasd, tsfc_wat, tprcp, tiice, ep, snwdph, qss_i, qss_w, snowmt, gflux, cmm, chh, evapi, evapw, hflxi, hflxw, islmsk, errmsg, errflg
subroutine	ice3lay
	This subroutine is the entity of three-layer sea ice vertical thermodynamics based on Winton(2000) [197] .

Detailed Description

General Algorithm

The model has four prognostic variables: the snow layer thickness \(h_s\), the ice layer thickness \(h_i\), the upper and lower ice layer temperatures located at the midpoints of the layers \(h_i/4\) and \(3h_i/4\) below the ice surface, respectively \(T_1\) and \(T_2\). The temperature of the bottom of the ice is fixed at \(T_f\), the freezing temperature of seawater. The temperature of the top of the ice or snow, \(T_s\), is determined from the surface energy balance. The model consists of a zero-heat-capacity snow layer overlying two equally thick sea ice layers (Figure 1). The upper ice layer has a variable heat capacity to represent brine pockets.

Fig.1 Schematic representation of the three-layer model

The ice model main program ice3lay() performs two functions:

• Calculation of ice temperature
  The surface temperature is determined from the diagnostic balance between the upward conduction of heat through snow and/or ice and upward flux of heat from the surface.
• Calculation of ice and snow changes
  In addition to calculating ice temperature changes, the ice model must also readjust the sizes of the snow and ice layers 1) to accommodate mass fluxes at the upper and lower surfaces, 2) to convert snow below the water line to ice, and 3) to equalize the thickness of the two ice layers.

Detailed Algorithm

Argument Table

local_name	standard_name	long_name	units	type	dimensions	kind	intent
im	horizontal_loop_extent	horizontal loop extent	count	integer	()		in
kice	vertical_dimension_of_sea_ice	vertical loop extent for ice levels, start at 1	count	integer	()		in
sbc	stefan_boltzmann_constant	Stefan-Boltzmann constant	W m-2 K-4	real	()	kind_phys	in
hvap	latent_heat_of_vaporization_of_water_at_0c	latent heat of evaporation/sublimation	J kg-1	real	()	kind_phys	in
tgice	freezing_point_temperature_of_seawater	freezing point temperature of seawater	K	real	()	kind_phys	in
cp	specific_heat_of_dry_air_at_constant_pressure	specific heat of dry air at constant pressure	J kg-1 K-1	real	()	kind_phys	in
eps	ratio_of_dry_air_to_water_vapor_gas_constants	rd/rv	none	real	()	kind_phys	in
epsm1	ratio_of_dry_air_to_water_vapor_gas_constants_minus_one	(rd/rv) - 1	none	real	()	kind_phys	in
rvrdm1	ratio_of_vapor_to_dry_air_gas_constants_minus_one	(rv/rd) - 1 (rv = ideal gas constant for water vapor)	none	real	()	kind_phys	in
grav	gravitational_acceleration	gravitational acceleration	m s-2	real	()	kind_phys	in
t0c	temperature_at_zero_celsius	temperature at 0 degree Celsius	K	real	()	kind_phys	in
rd	gas_constant_of_dry_air	ideal gas constant for dry air	J kg-1 K-1	real	()	kind_phys	in
ps	surface_air_pressure	surface pressure	Pa	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	in
t1	air_temperature_at_surface_adjacent_layer	surface layer mean temperature	K	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	in
q1	specific_humidity_at_surface_adjacent_layer	surface layer mean specific humidity	kg kg-1	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	in
delt	timestep_for_dynamics	time step	s	real	()	kind_phys	in
sfcemis	surface_longwave_emissivity_over_ice	surface lw emissivity in fraction over ice	frac	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	in
dlwflx	surface_downwelling_longwave_flux_absorbed_by_ground_over_ice	total sky surface downward longwave flux absorbed by the ground over ice	W m-2	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	in
sfcnsw	surface_net_downwelling_shortwave_flux	total sky sfc netsw flx into ground	W m-2	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	in
sfcdsw	surface_downwelling_shortwave_flux	total sky sfc downward sw flux	W m-2	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	in
srflag	precipitation_type	snow/rain flag for precipitation	flag	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	in
cm	surface_drag_coefficient_for_momentum_in_air_over_ice	surface exchange coeff for momentum over ice	none	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	in
ch	surface_drag_coefficient_for_heat_and_moisture_in_air_over_ice	surface exchange coeff heat & moisture over ice	none	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	in
prsl1	air_pressure_at_surface_adjacent_layer	surface layer mean pressure	Pa	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	in
prslki	ratio_of_exner_function_between_midlayer_and_interface_at_lowest_model_layer	Exner function ratio bt midlayer and interface at 1st layer	ratio	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	in
prsik1	surface_dimensionless_exner_function	dimensionless Exner function at the ground surface	none	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	in
prslk1	dimensionless_exner_function_at_surface_adjacent_layer	dimensionless Exner function at the lowest model layer	none	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	in
wind	wind_speed_at_lowest_model_layer	wind speed at lowest model level	m s-1	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	in
flag_iter	flag_for_iteration	flag for iteration	flag	logical	(ccpp_constant_one:horizontal_loop_extent)		in
use_lake_model	flag_for_using_lake_model	flag indicating lake points using a lake model	flag	integer	(ccpp_constant_one:horizontal_loop_extent)		in
lprnt	flag_print	switch for printing sample column to stdout	flag	logical	()		in
ipr	horizontal_index_of_printed_column	horizontal index of printed column	index	integer	()		in
thsfc_loc	flag_for_reference_pressure_theta	flag for reference pressure in theta calculation	flag	logical	()		in
hice	sea_ice_thickness	sea-ice thickness	m	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	inout
fice	sea_ice_area_fraction_of_sea_area_fraction	sea-ice concentration [0,1]	frac	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	inout
tice	surface_skin_temperature_over_ice	surface skin temperature over ice	K	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	inout
weasd	water_equivalent_accumulated_snow_depth_over_ice	water equiv of acc snow depth over ice	mm	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	inout
tsfc_wat	surface_skin_temperature_over_water	surface skin temperature over water	K	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	in
tprcp	nonnegative_lwe_thickness_of_precipitation_amount_on_dynamics_timestep_over_ice	total precipitation amount in each time step over ice	m	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	inout
tiice	temperature_in_ice_layer	sea ice internal temperature	K	real	(ccpp_constant_one:horizontal_loop_extent, ccpp_constant_one:vertical_dimension_of_sea_ice)	kind_phys	inout
ep	surface_upward_potential_latent_heat_flux_over_ice	surface upward potential latent heat flux over ice	W m-2	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	inout
snwdph	surface_snow_thickness_water_equivalent_over_ice	water equivalent snow depth over ice	mm	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	inout
qss_i	surface_specific_humidity_over_ice	surface air saturation specific humidity over ice	kg kg-1	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	in
qss_w	surface_specific_humidity_over_water	surface air saturation specific humidity over water	kg kg-1	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	in
snowmt	surface_snow_melt	snow melt during timestep	m	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	inout
gflux	upward_heat_flux_in_soil_over_ice	soil heat flux over ice	W m-2	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	inout
cmm	surface_drag_wind_speed_for_momentum_in_air_over_ice	momentum exchange coefficient over ice	m s-1	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	inout
chh	surface_drag_mass_flux_for_heat_and_moisture_in_air_over_ice	thermal exchange coefficient over ice	kg m-2 s-1	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	inout
evapi	kinematic_surface_upward_latent_heat_flux_over_ice	kinematic surface upward latent heat flux over ice	kg kg-1 m s-1	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	in
evapw	kinematic_surface_upward_latent_heat_flux_over_water	kinematic surface upward latent heat flux over water	kg kg-1 m s-1	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	in
hflxi	kinematic_surface_upward_sensible_heat_flux_over_ice	kinematic surface upward sensible heat flux over ice	K m s-1	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	in
hflxw	kinematic_surface_upward_sensible_heat_flux_over_water	kinematic surface upward sensible heat flux over water	K m s-1	real	(ccpp_constant_one:horizontal_loop_extent)	kind_phys	in
islmsk	sea_land_ice_mask_cice	sea/land/ice mask cice (=0/1/2)	flag	integer	(ccpp_constant_one:horizontal_loop_extent)		in
errmsg	ccpp_error_message	error message for error handling in CCPP	none	character	()	len=*	out
errflg	ccpp_error_code	error code for error handling in CCPP	1	integer	()		out