Ocean Currents and Regional Winds

Beyond the global wind belts, a variety of local and regional winds arise from more specific combinations of terrain and pressure. Foehn winds in the European Alps and their North American counterpart, chinook winds on the eastern slopes of the Rockies, form when air is forced to rise on the windward side of a mountain range, losing much of its moisture as precipitation, and then descends the leeward slope, warming adiabatically at a faster rate than it cooled on the way up; the result is a notably warm, dry wind that can melt snow rapidly, earning the chinook its nickname of "snow eater." The mistral, a cold, dry, often powerful wind, funnels down the Rhône valley in southern France toward the Mediterranean under the influence of pressure differences between the Bay of Biscay and the Gulf of Genoa, while the sirocco carries hot, dust-laden air northward from the Sahara across the Mediterranean into southern Europe. At a smaller, daily scale, monsoon-like breezes also occur along coastlines, where land heats and cools faster than the adjacent sea, producing an onshore sea breeze by day and an offshore land breeze by night, a miniature version of the same differential-heating principle that drives full seasonal monsoons.