pond_note.txt

!
!             SIS2 "getting-started" melt pond scheme
! 
! This melt pond scheme adds a single layer melt pond to each ice thickness
! category.  The layer does not have heat capacity.  It is assumed to be at
! freshwater freezing temperature and well mixed.  All pond surface fluxes
! are communicated directly to its bottom where surface energy balance is
! calculated.  The pond layer is advected and redistributed between ice
! thickness categories similarly to the snow and ice layers.  As is the case
! with snow, pond cannot exist without an ice layer below.  Basic descriptions
! of pond sources and sinks, and pond fraction for radiation treatments follow:
! 
! Source water:  Surface melting of snow and ice are the source of pond water.
! The runoff scheme keys on the total ice covered area.  This is the only
! interaction between category variables in the scheme.  The scheme uses r, the
! fraction of melt (r)etained given by the CICE5 scheme (p. 42):
! r = r_min + (r_max-r_min)*ice_area.  The controlling namelist
! parameters for r_min and r_max are pond_r_min and pond_r_max.
! 
! Freezing sink:  The surface energy budget continues to be performed at the
! top of the snow or ice when pond is present but the interface is fixed at
! freezing temperature and the residual between the fluxes on either side of the
! interface is made up with melt or freezing.  Freezing in this calculation is a
! sink of pond water.
! 
! Freeboard sink:  if the pond and snow are sufficiently massive to push the top
! of the sea ice below sea level, pond is dumped into the ocean until the ice
! top is brought back to sea level, or the pond is completely depleted.  This
! adjustment follows the CICE5 Hunke "level ice" pond scheme.
! 
! Porous-ice sink:  No through-ice drainage occurs until the ice average
! temperature exceeds a specified value.  The namelist parameter for this is
! pond_porous_temp.  Once this limit is exceeded the pond drains to a minimum
! value intended to represent coverage by ponds at sea level.  This scheme is
! a placeholder for the mushy-layer thermodynamics to be implemented later.
! 
! Pond fraction for radiation:  In the snow-free case we assume that pond
! fraction ranges between a specified minimum, where surface cavities below
! sea level are filled with pond water, and a specified maximum value.
! The pond depth and pond fraction are considered to be proportional as was
! found at the SHEBA site and incorporated into the Bailey melt pond
! parameterization.  This means that the pond fraction is proportional to
! the square root of the pond volume.  The pond volume has a maximum
! determined by the non-negative freeboard requirement.  This pond volume
! is associated with the maximum pond fraction, so less pond water is needed
! to cover thinner ice.
! 
! New namelist parameters: do_pond, pond_r_max, pond_r_min, pond_porous_temp,
! pond_frac_max, pond_frac_min
! 
! New diagnostics: hp, fp, pond_source, pond_sink_freeboard, pond_sink_porous,
! pond_sink_tot <only hp implemented so far, add pond transport diagnostics?>
!
! M. Winton (6/16)
!