Orographic lift

A gravity wave cloud pattern—analogous to a ship wake—in the downwind zone behind the Île Amsterdam, seen from above over the far southern Indian Ocean. The island generates wave motion in the wind passing over it, creating regularly spaced orographic clouds. The wave crests raise and cool the air to form clouds, while the troughs remain too low for cloud formation. Note that while the wave motion is generated by orographic lift, it is not required. In other words, one cloud often forms at the peak. See wave cloud.

Orographic lift occurs when an air mass is forced from a low elevation to a higher elevation as it moves over rising terrain.[1]: 162  As the air mass gains altitude it quickly cools down adiabatically, which can raise the relative humidity to 100% and create clouds and, under the right conditions, precipitation.[1]: 472 

Orographic lifting can have a number of effects, including precipitation, rain shadowing, leeward winds, and associated clouds.

  1. ^ a b Stull, Roland (2017). Practical Meteorology: An Algebra-based Survey of Atmospheric Science. University of British Columbia. ISBN 978-0-88865-283-6.