Any allergy-stricken southern Californian can tell you
when the Santa Ana winds are blowing. Recently, Santa Anas
blew through the southland at speeds in excess of 80
kilometers (50 miles) per hour.

A new image from the Multi-angle Imaging
SpectroRadiometer instrument on NASA’s Terra spacecraft shows
the pattern of airborne dust stirred up by Santa Ana winds on
February 9, 2002. These dry, northeasterly winds usually occur
in late fall and winter when a high pressure system forms in
the Great Basin between the Sierra Nevada and Rocky Mountain
ranges. The strength of the winds enables them to pick up and
relocate surface dust.

The new image, taken by the instrument’s 70-degree
forward-viewing camera, provides a graphic illustration of the
extent of this recurring phenomenon. The image can be viewed

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 San Diego

The Multi-angle Imaging SpectroRadiometer, built and
managed by NASA’s Jet Propulsion Laboratory, Pasadena, Calif.,
is one of several Earth-observing experiments aboard Terra,
launched in December 1999. The instrument acquires images of
the Earth at nine angles simultaneously, using nine separate
cameras pointed forward, downward, and backward along its
flight path. More information about the radiometer is
available at .