Pressure Gradient
Pressure gradient is the rate of change of atmospheric pressure over a horizontal distance. It is represented on weather charts by the spacing of isobars (lines of equal pressure) — closely spaced isobars indicate a steep pressure gradient; widely spaced isobars indicate a gentle gradient.
Pressure Gradient and Wind
Wind is driven by the pressure gradient force — air flows from high pressure toward low pressure to equalize the pressure difference. The steeper the pressure gradient (closer the isobars), the stronger the resulting wind. The Coriolis effect deflects the wind to the right in the Northern Hemisphere, causing it to flow parallel to the isobars (geostrophic wind) rather than directly across them.
Aviation Implications
- Strong pressure gradient → strong winds → significant headwinds, tailwinds, or crosswinds
- Tight isobar spacing on the GFA synoptic chart = expect significant wind at all levels
- Rapidly tightening gradient = frontal zone — expect wind shear and turbulence
- En route wind planning should reference upper wind charts which reflect actual predicted gradient effects
On the TC Written Exam
Pressure gradient is tested in the meteorology section. Know: isobars close together = steep gradient = strong wind; wind flows from high to low pressure (modified by Coriolis); steep gradient near fronts = turbulence.
Related Terms
See also: Cold Front, Warm Front, Low-Level Jet.