New data linked Indonesian wildfire flare-up to recent El Nino

New data linked Indonesian wildfire flare-up to recent ElNino

1 March 2007

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Indonesia — Scientists using NASA satellite and rainfalldata have linked the recent El Nino to the greatest rise in wildfire activity inIndonesia since the record-breaking 1997-98 El Nino.

El Nino is an abnormal warming of surface ocean waters inthe eastern tropical Pacific, which often brings significant shifts in globalweather patterns.

As rainfall sharply decreased during the last quarter of 2006 across the densetropical rainforests of Sumatra, Kalimantan, and Malaysia, the land becameexceptionally dry. This allowed wildfires to quickly spread, releasing largeamounts of soot and tiny dust particles called aerosols that brought unhealthypollution levels to the area.

The Measurements of Pollution in the Troposphere (MOPITT) instrument aboardNASA’s Terra satellite tracked the wildfire pollution plumes as they spread fromthe Indonesian islands into the Indian Ocean from September through November2006, and measured the associated increases in atmospheric carbon monoxidelevels.

“Droughts over Indonesia are often brought on by a shift in the atmosphericcirculation over the tropical Pacific associated with El Nino conditions,”said David Edwards, MOPITT project leader at the National Center for AtmosphericResearch, Boulder, Colo. “Although the current El Nino is rather weakcompared to that of 1997-98, we have found dramatic increases in wildfireactivity and corresponding pollution.”

Using MOPITT, Edwards and his team noted a distinct spike in carbon monoxidelevels across much of the Southern Hemisphere from the large number ofIndonesian fires at the end of 2006, greater than that associated with any ElNino event since 1997-98. The recent increase in wildfires was also captured byanother instrument, the Moderate Resolution Imaging Spectroradiometer, on NASA’sTerra and Aqua satellites, while NASA’s Global Precipitation Climatology Projectconfirmed a decline in Indonesian rainfall during the period.

Despite the number of factors that influence air quality across the region,wildfires play a very significant role. “Even though fires in South Americaand southern Africa typically produce the greatest amount of carbon monoxide,the pollution from Indonesian fires is likely responsible for most of theyear-to-year variation in pollution levels throughout the Southern Hemisphere,”Edwards said. Carbon monoxide is also involved in raising the concentration ofground-level “bad” ozone.

Some burning takes place every year in Indonesia, but the number and intensityof fires depends largely on rainfall and soil moisture conditions during thefire season, which usually runs September through November. Regional forestclearing practices also heighten the risk for wildfire development and spread.As lands are cleared, peat deposits – thick layers of partially decayedvegetation matter – build up. These deposits are vulnerable to wildfire and onceignited often result in a smoldering burn that releases copious amounts of smokeand carbon into the atmosphere until monsoon rains begin, typically in December.

“MOPITT is an especially valuable tool because it monitors carbon monoxide,a good indicator of pollution from combustion that remains in the atmosphere forseveral weeks, often traveling vast distances,” said Edwards. “Firesalso produce large relative changes in atmospheric carbon monoxide levels thatare detected quite well by satellites, so that we can easily assess the impactof fires on air quality and pollution levels.”

Carbon monoxide released from wildfires is a major player in regional airquality conditions, but significant amounts of carbon dioxide – the primarygreenhouse gas – are also released. As a result, wildfires also have thepotential to impact long-term climate.

The scientists are currently studying how they can use satellite data to examineNorthern Hemisphere wildfire outbreaks and corresponding pollution increases dueto periodic changes in weather patterns.

Source: Goddard Space Flight Center

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