The AMS defines meteorology as:
The study of the physics, chemistry, and dynamics of the earth's atmosphere, including the related effects at the air–earth boundary over both land and the oceans. Fundamental topics include the composition, structure, and motion of the atmosphere. The goals ascribed to meteorology are the complete understanding and accurate prediction of atmospheric phenomena.
From that definition, it would follow that every post tagged atmosphere should also be tagged meteorology, making the atmosphere tag redundant.