Special winds
Special winds are winds which blow under only certain circumstances. These may result from differential heating, from barriers to airflow, or from gravitational effects.
Differential heating is the motive force behind land breezes and sea breezes (or, in the case of larger bodies, lake breezes). Water is a rapid absorber/radiator of heat, whereas land not only absorbs heat more slowly but releases it over a greater period of time. The result is that, in locations where sea and land meet, heat absorbed over the day will be released more quickly by the water. Air contacting water cools. Over the land, heat is still being released into the air, which rises. This convective motion draws the cool sea air in to replace the rising air, resulting in a sea breeze. During the day, the roles are reversed. The land, cooled from a night of radiation, continues to soak up heat long after the heat capacity of the water has been reached. Warm air over the water rises, pulling cool air from inland to replace it. And so it goes.
Mountain breezes and valley breezes are due to a combination of differential heating and geometry. When the sun rises, it is the tops of the mountain peaks which receive first light, and as the day progresses, the mountain slopes take on a greater heat load than the valleys. This results in a temperature inequity between the two, and as warm air rises off the slopes, cool air moves up out of the valleys to replace it. This upslope wind is called a valley breeze. The opposite effect takes place in the afternoon, as the valley radiates heat. The peaks, long since cooled, transport air into the valley in a process that is partly gravitational and partly convective and is called a mountain breeze.
Mountain breezes are one example of what is known more generally as a Katabatic wind. These are winds driven by cold air flowing down a slope, and occur on the largest scale in Greenland and Antarctica. Most often, this term refers to winds which form when air which has cooled over a high, cold plateau is set in motion and descends under the influence of gravity. Winds of this type are common in regions of Mongolia and in glaciated locations.
Because katabatic refers specifically to the vertical motion of the wind, this group also includes winds which form on the lee side of mountains, and heat as a consequence of compression. Such winds may undergo a temperature increase of 20°C; or more, and many of the world's "named" winds (see list below) belong to this group. Among the most well-known of these winds are the chinook of Western Canada and the American Northwest, the Swiss foehn, California's infamous Santa Ana wind, and the Spanish mistral.
The opposite of a katabatic wind is an anabatic wind, or an upward-moving wind. The above-described valley breeze is an anabatic wind.
A widely-used term, though one not formally recognised by meteorologists, is orographic wind. This refers to air which undergoes orographic lifting. Most often, this is in the context of winds such as the chinook or the foehn, which undergo lifting by mountain ranges before descending and warming on the lee side.
See also: Beaufort scale, meteorology, climatology
Classical wind names
In ancient Greek mythology, the four winds were personified as gods. Roman writers later gave them Latin names. Note: the "north wind", for example, is the wind that blows from the north, not towards it.
