Major forces concerning motion of atmosphere and ocean of the earth

In a field of gravity
Gravity by air and water can be ignored.
Acceleration of gravity "g" may be assumed constant.
Rotating frame of reference=> Apparent forces need to be considered.
Centrifugal force associated with rotation of earth => included in gravity.
Coriolis' force acting on motion deviating from that of solid earth
(Shallow shell geometry: rotation around zenith axis is effective.)
Equation of motion: usually expressed as of per unit mass.
acceleration = total force / mass
Major forces for large-scale motion
Vertical: pressure gradient force & gravity
hydrostatic balance (0 = total force / mass)
Horizontal: pressure gradient force & Coriolis' force
Straight isobars ... geostrophic balance (0 = total force / mass)
Circular isobars ... centripetal accel. = total force / mass
Friction (viscosity) also important in the boundary layers near surface.