33.1.2.3 The fast way: MOM default explicit convection

1.

Compute all densities like in (1) of Marotzke.

2.

Compare all density pairs to find instabilities.

From here on, deal column by column with those grid points where an instability was found, performing the following steps:

3.

Mix the uppermost unstable pair.

4.

Check the next level below. If it is less dense than the mixture, mix all three. Continue incorporating more levels in this way, until a statically stable level is reached.

5.

Then check the level above the newly mixed part of the water column, to see whether this has become unstable now. If so, include it in the mixed part and go back to (3). If not, search for more unstable regions below the one we just mixed, by working your way down the water column comparing pairs of levels; if you find another unstable pair, go to (3).

Note that levels which have been mixed are from then on treated as a unit. This scheme has a slightly more complicated logical structure; it needs a few more integer variables and if statements to keep track of which part of the water column we have already dealt with. The advantage is that we only recompute the densities of those levels we need; levels which are not affected by the convection process are only checked once. The scheme includes diagnostics which allow to plot the convection depth at each grid point.