Chapter 11. Imbalance and Vertical Motion. (1) Wind-Parallel Accelerations. In order for wind to flow in a cyclonically curved manner, (an acceleration ) it has to be sub-geostrophic .
Imbalance and Vertical Motion
Gradient Force and the Coriolis Force are acting at right angles to the wind direction (they can only cause a change in direction)?
Above the friction layer, air will speed up if it has a component towards lower heights or lower pressures. Air will slow down if it is drifting toward higher heights or higher pressures.
The actual winds are stronger (super-geostrophic) than the geostrophic winds.
The Coriolis force is stronger than the PGF.
Thus, the Ageostrophic wind points the same way the wind is blowing.
The actual winds are weaker (sub-geostrophic) than the geostrophic winds.
The Coriolis force is weaker than the PGF.
Thus, the Ageostrophic wind points the opposite direction from which the wind is blowing.
The actual wind must be oriented toward lower pressures or lower contours, thus, the ageostrophic wind is pointed toward lower pressures; at right angles to the geostrophic wind.