What creates wind?

It's a simple question...... that has a non-trivial answer

• Wind is the result of different forces acting on a parcel of air, summarized nicely by Newton's second law:
  • F=ma
    • F = force (a push or pull)
    • m = mass of the object (parcel)
    • a = the resultant acceleration (speed up or slow down)

• If there is only one force, the net acceleration of the wind will be:

• However, if there are many forces involved, the net acceleration will be:

• Q: What are these forces in the atmosphere?