Cool to cold cP air alternating with warm mT air. Closer to ground where air is cold. Higher above ground where air is warm. B. Low pressure aloft in polar region, high pressure aloft over tropics. Generates consistent upper-level westerlies, due to geostrophic balance.
Winds move parallel to isobars, from west to east.
C. Upper-level winds form a belt around the polar zones of each hemisphere, with maximum wind speeds concentrated in the jet stream. Causes lots of weak cyclones to form and migrate rapidly from west to east. Little temperature or precipitation departure from normal. Pockets of warm and cold air bulge into midlatitudes. Causes fewer, larger cyclones to form, migrate slowly from west to east.