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Santa Ana: a Dangerous Wind

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Santa Ana: a Dangerous Wind ample, they are called mistrals in southern elevation. France, chinooks in the Rocky Mountains In the case of California’s Santa Anas, Geography and boras in northeast Italy and Slovenia. the air that reaches the coast may be very In The In the U.S. Southwest, the katabatic winds hot. Air that descends in elevation heats are called Santa Ana winds. through a process known as adiabatic News™ Winds blowing out of high pressure warming. As air descends, it is compressed cells generate katabatic winds, often be- and it warms at 5.5 degrees Fahrenheit per ginning as cold winds. These high pres- 1,000 feet (1 degree C/100 m). sure cells, containing cold, dense air, may Additionally, katabatic winds are very, Neal Lineback become situated over mountains or high very dry winds. Having originated as and Mandy Lineback Gritzner plateaus. Because air tends to move from cold, dry air and then warmed adiabati- high pressure areas toward surrounding cally, this air may arrive at sea level with low pressure, the air rushes outward from a relative humidity below 10 percent. The SANTA ANA: the center of the high pressure area and temperature of typical Santa Ana wind gravity pulls it into the valleys below. The may exceed100 F (37.8 C) by the time it ap- A DANGEROUS air’s relative weight causes it to hug the proaches sea level. ground. Santa Ana winds normally occur in WIND As the air fl ows toward the lowlands, its Southern California in the fall season fol- Blistering Santa Ana winds whipped velocities increase. The relatively cold air lowing a normally dry summer. These fi res across more than half a million acres travels beneath warmer, less dense air as winds result from a high pressure air (202,342 hectares) in Southern California in it descends toward the valleys or coast. Al- mass, or cell, forming over the Colorado mid-October. The fi res Plateau and the Basin torched 1,790 homes in Desert Winds Fuel California Fires and Range in Utah, Ari- the area, sent more than zona and Nevada. Santa 500,000 people scurry- Santa High pressure cells Barbara Clarita ing from their homes in the Northern Hemi- 10201 and left 4,400 in make- San 0 sphere rotate clockwise, Bernardino 2 shift shelters. At least 0 spilling air out in all seven people died in the directions. Northeast blazes, including four winds from such cells California Wildfires 102410 suspected Mexican il- 24 pour through passes in Active Contained San legal immigrants found Diego the San Gabriel and San near the U.S.-Mexico The Christian Science Monitor, 10-24-2007 10281 Bernadino mountains 0 2 border. 8 and fl ow downslope to- Santa Ana RockyR Mountians ward Los Angeles, San 10321 o winds are hot, dry 0 Diego and Tijuana (Baja SierraS Nevada 3 c 2 k winds that characteristi- i California) at speeds e GreatG r e a t 1036103 y cally appear in Southern r 6 of 35 knots (65 kph) or M California and northern r greater. a BasinB a s i n o Baja California in late N u As Santa Ana winds H n e summer and fall. But, t are channeled through v i similar winds also occur a a mountain passes into in other Mediterranean- d n Southern California, a s type climates around they can briefl y ap- the world, often fanning proach hurricane force. 11028 0 the brushfi res common 2 Then they roar down 8 in these regions. the mountain slopes The Santa Ana winds Inset into the valleys and 102410 are a type of katabatic 24 canyons. The combina- wind. The name ka- 10201 tion of wind, heat and 020 Anticyclonic Wind Flow tabatic comes from the Pacific dryness turns chaparral Santa Ana Winds Greek word kataba- Ocean into explosive fuel re- tikos, meaning “going 0 400 mi sulting in the infamous downhill.” Katabatic is 0 400 km wildfi res for which the a generic term used for ©2007 region is renowned. downslope winds fl ow- R.HuertaGeographyG eography inin thethe NewsNews 11/16/0711/16/07 And that is Geography ing from high elevations in the News™. Novem- of mountains, plateaus ber 16, 2007. #911. and hills down their Sources: http://news.yahoo.com/s/ap/california_wildfires; Co-authors are Neal slopes to the valleys or http://www.weatheronline.co.uk/reports/wxfacts/Katabatic-winds.htm; Lineback, Appalachian plains below. and GITN 461, “How an Ill Wind Blows,” December 17, 1998. State University Professor Katabatic winds have Emeritus of Geography, different names de- and Geographer Mandy pending upon where in the world they are though the air may be cold near its origin, Lineback Gritzner. University News Director located and how they are formed. For ex- it begins to heat rapidly as it descends in Jane Nicholson serves as technical editor. ©2007 Maps.com.
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