monarchs.physics.percolation.calc_saturation

monarchs.physics.percolation.calc_saturation(cell, v_lev_in, end=False)

Determine whether the firn is saturated, calculating upwards from a vertical level specified by v_lev_in. If the firn is saturated, then water can no longer percolate downward, and we need to set the cell attribute saturation to True at the relevant vertical level. Any water that is left over is then moved upwards to the next vertical layer, and the process repeats until either all water is accounted for (i.e. can remain in the current layer), or we reach the surface (i.e. we have exposed water and a lake will begin to form). This function can also be called to ensure that water is simply moved to the correct place due to changes from other effects (e.g. refreezing), without determining whether it is saturated. The variable end determines whether this is the case.

Parameters:

• cell (numpy structured array) – Element of the model grid we are operating on.

• v_lev_in (int) – Vertical level from which to determine whether the cell is saturated.

• end (bool, optional) – Flag that determines whether the function is called at the end of the percolation step, or not. If it is (i.e. the flag is True), then instead of saying the firn is saturated, we say that there is meltwater present. This allows the water to percolate again at the next timestep, and allows us to reuse most of the same logic for this case where there may be water that can percolate again later. Default False.

Return type:

None (amends cell inplace)

Raises:

ValueError – If lake depth goes negative, model is in an unphysical state so we throw an error.