concept

Ekman spiral (atmospheric)

The pattern in which wind both speeds up and turns with height through roughly the lowest kilometre of the atmosphere, typically rotating through 15–45° in total. The cause is that surface friction weakens as you rise: near the ground friction drags the wind slower and swings it toward the low pressure, while higher up friction loses its voice until the wind recovers the pure geostrophic direction along the isobars. Do not conflate this with Ekman transport, which is the ocean version of the same physics, with water layers turning with depth rather than air layers turning with height. One friction-plus-Coriolis problem, two fluids.