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Wildfires
Introduction
The increased risk of wildfires (MODIS fire data) (TRMM fire data) due to drought conditions (TOVS rain data) (TRMM TMI rain data) is one of the greatest ENSO-related threats to forests and natural vegetation (Pathfinder NDVI data). Drought raises the flammability of vegetation and creates other conditions for the spread of fires. Drought conditions lead to an increased number of fires, area burned, and intensity of burning. Wildfires increase the levels of carbon dioxide in the atmosphere, thus contributing to global warming. Fires may also reduce biological diversity, destroy wood and other forest products, and emit smoke (TOMS Aerosol Index data) and air-polluting gases harmful to human health.
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Fires on the Island of Borneo During El Niño |
Woodland and Grassland Fires in Southern Africa During La Niña |
Fires are a significant source of gases and aerosols introduced into the atmosphere and are a major disturbance of vegetation cover. Man-caused fires contribute up to 50, 40, and 16 percent of the total emissions for carbon monoxide, carbon dioxide. and methane, respectively.
El Niño Wildfires
When the severe El Niño struck in 1982 to 1983, Australia added wildfires to its worst drought of the century. During the El Niño of 1997-98, Indonesia and Australia suffered massive forest and peat fires that blackened skies across southeast Asia. Pollution from Indonesian fires during 1997 reached India (TOMS Aerosol Index data). Canada suffered from a particularly intense outbreak of fires burning the boreal forests. In Mexico, rogue fires scorched a treasured cloud forest. During the following La Niña (August 20 to September 20, 2000), wildfires in southern Africa burned some 64.6 million hectares and released an estimated 232.4 Tg of carbon dioxide.
La Niña Wildfires
However, in the United States a nationwide survey suggested that the relation between wildland fires and the ENSO phenomenon is statistically significant only in the southeastern United States. In the Ponderosa pine forests of the southwestern United States, tree growth is enhanced during El Niño conditions; extensive fires in early summer of 1989 followed a dry winter and spring associated with an unusually cold episode in the tropical Pacific (La Niña). The U.S. National Interagency Fire Center said that "As a result of La Niña and its influence on weather patterns [... a wet winter in the northwestern United States and dry conditions along the southern tier of the country from California to Florida.], a combination of dry fuels and dry, hot weather led to what some are declaring one of the most serious wildland fire seasons in U.S. history. The absence of the seasonal monsoons in the Southwest, the dry vegetation and record-low fuel moistures, and the persistently hot weather across much of the West, culminated in a wildland fire season that began early, became intense, and is expected to last unusually long." The long La Niña of 1998-2001 set conditions for the western U. S. wildfire seasons of 2000 and 2002 (U.S. Fire Season Statistics), and also resulted in millions of square kilometers of burned areas in countries around thw world (GBA2000 Statistics).
Aerosols
Wildfires produce airborne aerosols. These tiny airborne particles of pollution have been shown to modify developing thunderclouds by increasing the quantity and reducing the size of the ice crystals within them. Airborne aerosols reduce the size of ice crystals in thunderclouds, by as much as 20 percent. As a result of their smaller size, the ice crystals evaporate from a solid state directly into a gas, instead of falling as rain. Thus wildfires help to perpetuate drought conditions.
Jump to 'Wildfires' List of Web Sites
Disclaimer: NASA offers these suggested sites for additional information regarding effects of El Niño and La Niña teleconnection events. Web access is required to reach these sites. Link existence and contents are not under the control of the EOSDIS Science Operations Office.
Wildfires Web Sites
