I believe drag is the result of friction, everything on Earth and any other bodies have friction. Friction from water molecules and air molecules is very minute but should be considered, it is mainly land and the obstructions that lie on top of it. Downbursts don't take down the wind from the upper atmosphere, they create it. A good example of a meso-vortice, take a cup spin it around with a spoon then move the spoon the other way quickly. You can see little meso-vortices, meso is simply a term that describes the size of the weather. But your right frictional drag makes vortices in the eye.