Terrain Following Coordinates

In previous posts I have mentioned a density current simulation. I have modified the code substantially, and have begun introducing terrain following coordinates. In the video you should see the cool bubble (this time red) fall because of its over density. Once reaching the surface it spreads out and a density current begins to travel along the surface. Notice how the density current slows before cresting the hill. This is the same reason a ball rolling up a surface would slow down. As the current comes down the other side of the mountain hill you can see it accelerates and produces additional sheer with the atmosphere above.

Why terrain following coordinates? Weather models don't like coordinates that don't follow terrain. They can produces waves/modes in the model that are hard to damp. Terrain also influences the atmosphere significantly. My research mainly focuses on the ability of terrain to produce waves. While storm chasing terrain can influence the generation of a thunder storm by lifting air, or can induce 'mesoscale' circulations (like the infamous palmer divide).