The hydrometeors a microphysics scheme moved across each z-face by sedimentation during its most recent Advance on a level.
down(i,j,k,n) is the amount of the conserved state component cons_comp[n] (rho*q, so kg m^-3 for a mixing ratio and m^-3 for a number concentration) that crossed z-face (i,j,k) downward during that Advance, per unit horizontal area: kg m^-2 or m^-2. Face k is the bottom face of cell k, so the face at the domain bottom holds what reached the ground. down is defined on the level's grids, z-nodal, and is zeroed at the start of every Advance.
A scheme records the fluxes its cell updates actually used, so that (up to the clipping of negative values) the change of rho*q*dz in a cell is down on its top face minus down on its bottom face. Schemes whose sedimentation has no face fluxes of its own (the semi-Lagrangian WSM6/WDM6 solvers) reconstruct them with sedimentation_add_column_sums below. The inflow a fine patch receives through its top face, handed to a scheme for one Advance (NullMoist::Set_Sed_Inflow). It is z-nodal on the level's grids, with the components of the level's SedimentationFlux plus a flag, comp inflow_flag_comp(): where the flag is 1, face (i,j,k) is the top of a fine column that stops short of the domain top, and component n holds the amount of cons_comp[n] entering through it during the Advance, per unit horizontal area (as SedimentationFlux::down). Elsewhere everything is zero.
