Satellites See Double Jeopardy for Socal Fire Season

Extensive and persistent rains between Jan. 24 and Jan. 27, 2013, significantly increased soil moisture and enhanced vegetation growth in Southern California. The upper panel represents changes in soil moisture measured by the Indian Oceansat-2 satellite on Jan. 25, 2013. Wet areas -- those with more than a 10-percent increase in soil moisture -- are shown in yellow. The lower panel depicts vegetation conditions as represented by the Normalized Difference Vegetation Index measured by NASA's Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on NASA's Aqua spacecraft on Feb. 25, 2013, when vegetation had been growing rapidly since the period of rain in January. Darker green areas represent more vegetation.

New insights into two factors that are creating a potentially volatile Southern California wildfire season come from an ongoing project using NASA and Indian satellite data by scientists at NASA's Jet Propulsion Laboratory, Pasadena, Calif.; and Chapman University, Orange, Calif.

The scientists tracked the relationship between rainfall and the growth and drying-out of vegetation in recent months, during an abnormally dry year. They found the timing of rains triggered regional vegetation growth in January and early February, which then dried out faster than normal during a period of low rainfall, strong winds and high temperatures in March and April. The combination likely elevates wildfire risks by increasing available fuel.

The two institutions are combining satellite datasets to monitor moisture changes in vegetation and soil across Southern California's vast wilderness areas in order to identify early warning signs of potential wildfires. The scientists are using measurements of soil moisture change from the Indian Oceansat-2 satellite scatterometer (OSCAT) and of vegetation stress from the Moderate Resolution Imaging Spectroradiometer (MODIS) sensor on NASA's Aqua satellite.

The MODIS instrument is managed by NASA's Goddard Space Flight Center, Greenbelt, Md. For further information, access the MODIS home page at http://modis.gsfc.nasa.gov.

The California Institute of Technology in Pasadena manages JPL for NASA.