# Ekman boundary conditions

From AMS Glossary

## Ekman boundary conditions

These are the four mathematical/physical conditions used when integrating the fourth-order differential equations governing the Ekman layer.

These conditions are where (

*U*,*V*) are the horizontal winds to the east and north, respectively;*z*is height above the surface; and*G*is the geostrophic wind speed. The first two conditions state that friction at the ground causes the wind speed to be zero there, while the last two conditions state that the winds become geostrophic where friction is negligible at large distances above the surface.