Katabatic wind (from the Greek. Κατάβασις , katabasis - descent, decline), also falling - dense and cold air flow directed down the slopes of the earth's surface (from mountain passes ), as well as descending jets of cold air in cumulonimbus clouds .
Not all winds blowing downhill are katabatic. For example, winds such as hair dryer , shinuk, or bergwind are the winds of rain shadows , where as they rise from the windward side of a mountain range, the air loses moisture and descends dry and warm on the leeward side. The katabatic wind brings a cooling to the foot of the mountains, which is not compensated by adiabatic heating when lowering the air masses. Katabatic winds can reach hurricane speeds - in the dry Mac-Murdo valleys they accelerate to 320 km / h.
Falling winds are known in many mountainous countries and coasts. In Norway, this wind is called elvegust , in Rio de Janeiro - terre-altos , in Japan - orosi , in southern California - Santa Ana wind . The most pronounced are boron , glacial wind , stock wind, mistral and others.
Formation
The formation of katabatic winds is due to the cooling of the air on mountain plateaus , summits, glaciers or even hills. As the density of air increases with a decrease in its temperature , gravity pulls it down the slope. As it descends, the wind heats up adiabatically, with the final temperature depending on the region of the source and the height of the descent. For example, the Santa Ana wind may become hot by the time it reaches the sea, and in Antarctica the stock wind is always very cold.
Most often katabatic winds blow from the ice-covered hills of the Antarctic and Greenland . In Greenland, such winds are called pitaraq ; they blow especially strongly when a low pressure area forms near the coast. On the archipelago of Tierra del Fuego in South America , as well as in Alaska , the harbor wind, called “ williwaw ”, is especially dangerous for ships in harbors. It occurs on the snowy and icy fields of coastal mountains and flies to the coast at a speed of 200-300 km / h.
See also
- Anabatic wind
Links
- Wikimedia Commons has media on Katabatic Wind
- Encyclopedia of the winds - katabatic falling wind
- Weather AZ - Katabatic Winds By Bill Giles OBE
- Nasa Katabatic Winds Rake Antarctica's Terra Nova Bay (Eng.) . Earth Observatory (November 10, 2009). The appeal date is November 11, 2009.