Supercooled_water

Maximum liquid water content in a soil layer below the freezing point, following the supercooled-soil-water freezing-point depression treatment of Niu and Yang (2006). Below T_f, liquid coexists with ice via the matric-potential / latent-heat balance of Oleson et al. (2010) Eq. 4.58; above T_f, the layer holds the fully-saturated maximum Δz·θ_sat·ρ_liq. Migrated from UrbanCanopy.jl@9200edd4 src/roof_wall_road_snow_temperatures.jl:949 (`FreezingPointDepression` @component). Parameterized as observed-only: T_i, θ_sat, Δz, ψ_sat, B_i, ρ_liq are inputs (parameters); w_liq_max is the algebraic output.