I have little knowledge in fluid dynamics, so this may be naive. But I have a question while reading a textbook about the Coriolis force, by which the rotation of the earth from west to east changes the air circulation pattern.
The text states that
As a ring of air about the earth atmosphere moves toward the poles, its radius decreases. In order to maintain angular momentum, the velocity of air increases with respect to the land surface, thus producing a westerly air flow
The converse is true for a ring of air moving towards the equator -- it forms an easterly air flow.
I can't understand why an easterly flow should be generated in the "converse" part. To me, suppose we have a satellite staying put (w.r.t to earth coordinate system) above the earth. Since the earth is rotating west-to-east, the satellite should move east-to-west (westerly) relative to the earth surface, right?
How does the Earth rotation cause a easterly movement?
-- EDIT --
I was probably confused about the word "easterly", and thought it meant "to the east". As @rob pointed out, it means "from the east". In that case, the question still remains, how does the Earth rotation cause a "westerly" (i.e. west-to-east) movement as described in the first half of the quoted text?
(I really don't see the symmetry in the "conversely" part of the reasoning in terms of physics).