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| Titel |
Fire, drought and El Niño relationships on Borneo (Southeast Asia) in the pre-MODIS era (1980–2000) |
| VerfasserIn |
M. J. Wooster, G. L. W. Perry, A. Zoumas |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
1726-4170
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| Digitales Dokument |
URL |
| Erschienen |
In: Biogeosciences ; 9, no. 1 ; Nr. 9, no. 1 (2012-01-16), S.317-340 |
| Datensatznummer |
250006668
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| Publikation (Nr.) |
 copernicus.org/bg-9-317-2012.pdf |
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| Zusammenfassung |
| Borneo (Indonesia) is Earth's third largest island, and the location of both
extensive areas of rainforest and tropical peatlands. It is the site of both
regular (seasonal) biomass burning associated with deforestation, land cover
change and agricultural production preparations, and occasional, but much
more severe, extreme fire episodes releasing enormous volumes of carbon from
burning vegetation and peat. These extreme fire episodes are believed to
result from anthropogenic practices related to (the still ongoing)
forest degradation and clearance activities, whose impact with regard to
fire is magnified by the effects of El Niño related drought.
Since 2000, data from the MODIS Earth Observation satellite instruments have
been used to study fire on Borneo, but earlier large fire events remain less
well documented. Here we focus on a series of large fire episodes prior to
the MODIS era, and specifically a 20 yr period covering both the two
strongest El Niño events on record (1997–1998 and 1982–1983), along with an
unprecedented series of more frequent, but weaker, El Niños. For the
five El Niños occurring between 1980 and 2000, we develop quantitative
measures of the fire activity across Borneo based on active fire counts
derived from NOAA AVHRR Global Area Coverage (GAC) Earth Observation
satellite data. We use these metrics to investigate relationships between
the strength and timing of the El Niño event, the associated drought,
and the fire activity. During each El Niño, we find areas of major fire
activity confined within two or three fire sub-seasons (separated by
monsoons) and focused in parts of South and Central Kalimantan, and
sometimes also in East and/or West Kalimantan. For each El Niño we
investigate various lag correlations, and find relationships of similar
strength between monthly rainfall deficit and fire, but of more variable
strength between indices of El Niño strength (ENSO indices) and rainfall
deficit. The two strongest El Niño episodes (1982–1983 and 1997–1998) are
accompanied by the most abundant fires (two and three times the active fire
count seen in the next largest fire year), and the strongest correlations
between measures of El Niño strength, rainfall and fire. We find the
most significant positive statistical association between an ENSO index and
fire activity to be that between the 16-month (first and second fire
sub-seasons) cumulative NINO3 anomaly and the simultaneously recorded
active fire count (r = 0.98, based on the five El Niño episodes between
1980 and 2000), although we find a negative association of equal strength
between the cumulative NINO4 index and active fire count when considered
over the entire two year duration of each El Niño episode (first, second
and third fire sub-seasons). Our results confirm that the El Niño
phenomenon, via its effect on precipitation, is a primary large-scale,
short-term climatic factor that has a strong control on the magnitude of the
fire activity resulting from the numerous land cover changes, agricultural
preparation practices and human-caused ignitions occurring annually across
Borneo. The results also suggest that ENSO forecasting maybe a realistic means of
estimating the extent and magnitude of this fire activity some months in
advance, thus offering some potential for forecasting effects on the
remaining forest and peatland resource and the regional atmosphere. |
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