Definition
The rate of change of atmospheric pressure with horizontal distance, shown on a surface weather map by the spacing of isobars. A steep (or strong) pressure gradient exists where isobars are close together, indicating a large pressure change over a short distance; a weak gradient exists where isobars are spaced far apart.
Plain English
How quickly air pressure changes from one place to another across the map. When the lines on a weather chart are packed close together, pressure is changing fast over a short distance. When they're spread out, pressure barely changes as you move across the area.
Context Anchor
Seen when reading surface weather maps and comparing the spacing between pressure lines to understand expected wind strength.
Derivation
From Latin gradus, meaning 'step.' A gradient is a measure of how steeply something changes as you step from one point to the next — here, how steeply pressure changes across the ground.
Why Pilots Care
Stronger pressure gradients produce stronger winds, which affect takeoff, landing, turbulence, and fuel planning.
Analogy
Think of isobars like contour lines on a hiking map. Lines close together mean a steep slope; lines far apart mean gentle terrain. With pressure, a 'steep slope' means strong wind.
Grounding Statement
When pressure drops quickly from one area to another, air tends to move more strongly from the higher-pressure area toward the lower-pressure area.
Intuition Check
Pressure gradient does not mean the pressure at one point. It means how quickly pressure changes across distance.
Example Sentence 1
The tightly packed isobars over the Midwest indicated a steep pressure gradient, so the pilot expected strong surface winds along the route.
Example Sentence 2
Before departure the pilot reviewed the pressure gradient to anticipate headwinds along the route.