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Envisat Captures California Ablaze
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Envisat Captures California Ablaze

October 23, 2007

This Envisat image captures the smoke arising from raging wildfires burning in Los Angeles, California. Nearly a dozen wildfires driven by strong easterly winds ripped across Southern California on Sunday, killing one person and forcing thousands to evacuate their homes.

A state of emergency has been declared in seven counties hit by the blazes: Los Angeles, San Diego Orange, Riverside, San Bernardino, Santa Barbara and Ventura.

Santa Ana winds are a California firefighter's nightmare. These blustery, dry, and often hot winds blow out of the desert and race through canyons and passes in the mountains on their way toward the coast. The air is hot not because it is bringing heat from the desert, but because it is flowing downslope from higher elevations. As fall progresses, cold air begins to sink into the Great Basin deserts to the east of California. As the air piles up at the surface, high pressure builds, and the air begins to flow downslope toward the coast. When winds blow downslope, the air gets compressed, which causes it to warm and dry out. In fact, the air can warm at a rate of 10 degrees Celsius per kilometer of descent (29 degrees Fahrenheit per mile). Canyons and passes funnel the winds, which increases their speed. Not only do the winds spread the fire, but they also dry out vegetation, making it even more flammable.

Image acquired 22 October 2007 at 17:52 UTC by the MERIS (Medium Resolution Imaging Spectrometer) instrument aboard ESA's Envisat satellite while working in Full Resolution mode to provide a spatial resolution of 300 metres. MERIS images are available on ESA's MIRAVI website, which gives access to Envisat's most recently acquired images.