Southern Californias Santa Anas are dry, north-easterly winds having
speeds in excess of 25 knots (46 kilometers/hour). Santa Ana conditions
are commonly associated with gusts of more than twice this level. These
offshore winds usually occur in late fall and winter when a high
pressure system forms in the Great Basin between the Sierra Nevadas and
the Rocky Mountains. The air warms as it flows downslope from the high
plateau, and its speed increases dramatically when forced through narrow
canyons and mountain passes. Due to Southern Californias uneven
terrain, the strength of the winds varies greatly from place to place,
and the Santa Anas can be sufficiently strong to pick up surface dust.
This view from the Multi-angle Imaging SpectroRadiometer shows the
pattern of airborne dust stirred up by Santa Ana winds on February 9,
2002. The image is from MISRs 70-degree forward-viewing camera, and
airborne particulates are especially visible due to the cameras oblique
viewing angle. Southeast of the Los Angeles Basin, a swirl of dust,
probably blown through the Banning Pass, curves toward the ocean near
Dana Point. The largest dust cloud occurs near Ensenada, in Baja
California, Mexico. Also visible in this image is a blue-gray smoke
plume from a small fire located near the southern flank of Palomar
Mountain in Southern California.
This image represents an area of about 410 kilometers x 511 kilometers.