Summary of Surface Water Phase Change:

Headline: Surface Water

When the surface water temperature, Th2osfc, falls below the freezing temperature, Tf, the energy available for freezing is calculated as:

Hh2osfc = (∂h/∂T)(Tf - Th2osfc^n) - (ch2osfc Δzh2osfc /Δt)(Tf - Th2osfc^n)

Where ch2osfc is the volumetric heat capacity of water, and Δzh2osfc is the depth of the surface water layer.

If Hm = Hh2osfc Δt/Lf > 0, then Hm is removed from the surface water and added to the snow column as ice:

Hh2osfc^(n+1) = Hh2osfc^n - Hm
wice,0^(n+1) = wice,0^n + Hm

The snow depth is also adjusted to account for the additional ice mass:

Δzsno = Hm/ρice

If Hm is greater than Wsfc, the excess heat (Lf(Hm - Wsfc)/Δt) is used to cool the snow layer.