noun
gradient
GRAY-dee-unt/ˈɡreɪdiənt/
The rate of change in a quantity across distance.
The ramp's gradient describes how its height changes along its length.

Etymology
The noun probably developed from grade meaning a slope. That slope sense provides a concrete image for change in level, color, or intensity across a distance.
In context
we can do exactly the same in this case looking at the horizontal pressure gradient which is basically the rate at which atmospheric pressure changes with distance
More examples
- The road's steep gradient makes cycling uphill difficult.
- A pressure gradient drives air from high-pressure areas toward low-pressure areas.
- Researchers measure salinity gradients where the river meets the ocean.
Forms
gradient · gradients