Ocean temperatures can predict Amazon fire season severity

NASA: By analyzing nearly a decade of satellite data, a team of scientists led by researchers from the University of California, Irvine and funded by NASA has created a model that can successfully predict the severity and geographic distribution of fires in the Amazon rain forest and the rest of South America months in advance.

Though previous research has shown that human settlement patterns are the primary factor that drives the distribution of fires in the Amazon, the new research demonstrates that environmental factors – specifically small variations in ocean temperatures – amplify human impacts and underpin much of the variability in the number of fires the region experiences from one year to the next.

"Higher than normal sea surface temperatures in the Atlantic and the Pacific proved to be red flags that a severe fire season was on its way in four to six months," said Yang Chen, the University of California, Irvine, scientist who led the research. Chen and his colleagues found temperature changes of as little as .25°C (.45°F) in the North Atlantic and 1°C (1.8 °F) in the Central Pacific can be used to forecast the severity of the fire season across much of the Amazon.

The researchers believe that unusually warm sea surface temperatures cause regional precipitation patterns to shift north in the southern Amazon during the wet season. "The result is that soils don't get fully saturated. Months later, humidity and rainfall levels decline, and the vegetation becomes drier and more flammable," said James Randerson, a scientist at University of California, Irvine who co-authored the study.

To establish the connection between fire activity and sea surface temperatures the researchers analyzed nine years of fire activity data collected by Moderate Resolution Imaging Spectroradiometer instruments (MODIS) on NASA's Terra and Aqua satellites and compared the number of fires to records of sea surface temperatures maintained by the National Oceanic and Atmospheric Administration. Years with anomalously cool ocean temperatures had fewer fires, while years that experienced unusually warm ocean temperatures experienced more fires. The team also looked for and found changes in precipitations patterns as measured by the Tropical Rainfall Measuring Mission (TRMM), a satellite managed jointly by NASA and the Japan Aerospace Exploration Agency (JAXA)....

In this image, intact forest is deep green, while cleared areas are tan (bare ground) or light green (crops, pasture, or occasionally, second-growth forest). The fish bone pattern of small clearings along new roads is the beginning of one of the common deforestation trajectories in the Amazon. NASA image