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.
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 County.
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 http://www-misr.jpl.nasa.gov .
JPL is a division of the California Institute of Technology in Pasadena.