METEOROLOGIST JEFF HABY
The geostrophic wind is the wind flow that occurs in the middle latitudes aloft in the troposphere. The winds have a more difficult time
obtaining geostrophic balance in the equatorial latitudes since the Coriolis force is weak. The geostrophic balance also does not occur
at and near the surface since the force of friction is significant there and the geostrophic balance does not occur in a curved flow
since a centrifugal force is introduced in that situation. What the geostrophic wind includes is a balance between the PGF (Pressure Gradient Force)
and the Coriolis force. This flow results in the wind staying parallel to height contours. The PGF is the force resulting
in the pressure difference between higher and lower pressure. The PGF points directly from high to low pressure (or heights). The Coriolis force
results from the spin of the Earth and is directed to the right of the path of motion in the Northern Hemisphere.
The diagram below shows an example of geostrophic balance in the Northern Hemisphere. The wind flows with higher pressure (heights) to the right
of the path of motion and lower pressure (heights) to the left of the path of motion. The PGF points from higher toward lower pressure (heights)
and the Coriolis points to the right of the path of motion (which is equal in magnitude but in the opposite direction of the PGF in order
to balance it). The height contour spacing determines the magnitude of the wind. Closer spacing results in stronger wind.