 |
| Titel |
Tropical biomass burning smoke plume size, shape, reflectance, and age based on 2001–2009 MISR imagery of Borneo |
| VerfasserIn |
C. S. Zender, A. G. Krolewski, M. G. Tosca, J. T. Randerson |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1680-7316
|
| Digitales Dokument |
URL |
| Erschienen |
In: Atmospheric Chemistry and Physics ; 12, no. 7 ; Nr. 12, no. 7 (2012-04-11), S.3437-3454 |
| Datensatznummer |
250011021
|
| Publikation (Nr.) |
 copernicus.org/acp-12-3437-2012.pdf |
|
|
|
|
|
| Zusammenfassung |
| Land clearing for crops, plantations and grazing results in anthropogenic
burning of tropical forests and peatlands in Indonesia, where images of
fire-generated aerosol plumes have been captured by the Multi-angle Imaging
SpectroRadiometer (MISR) since 2001. Here we analyze the size, shape, optical
properties, and age of distinct fire-generated plumes in Borneo from
2001–2009. The local MISR overpass at 10:30 a.m. misses the afternoon peak of
Borneo fire emissions, and may preferentially sample longer plumes from
persistent fires burning overnight. Typically the smoke flows with the
prevailing southeasterly surface winds at 3–4 m s−1, and forms ovoid
plumes whose mean length, height, and cross-plume width are 41 km, 708 m,
and 27% of the plume length, respectively. 50% of these plumes have
length between 24 and 50 km, height between 523 and 993 m and width between
18% and 30% of plume length. Length and cross-plume width are
lognormally distributed, while height follows a normal distribution. Borneo
smoke plume heights are similar to previously reported plume heights, yet
Borneo plumes are on average nearly three times longer than previously
studied plumes. This could be due to sampling or to more persistent fires and
greater fuel loads in peatlands than in other tropical forests. Plume area
(median 169 km2, with 25th and 75th percentiles at 99 km2 and
304 km2, respectively) varies exponentially with length, though for
most plumes a linear relation provides a good approximation. The
MISR-estimated plume optical properties involve greater uncertainties than
the geometric properties, and show patterns consistent with smoke aging.
Optical depth increases by 15–25% in the down-plume direction,
consistent with hygroscopic growth and nucleation overwhelming the effects of
particle dispersion. Both particle single-scattering albedo and
top-of-atmosphere reflectance peak about halfway down-plume, at values about
3% and 10% greater than at the origin, respectively. The initially
oblong plumes become brighter and more circular with time, increasingly
resembling smoke clouds. Wind speed does not explain a significant fraction
of the variation in plume geometry. We provide a parameterization of plume
shape that can help atmospheric models estimate the effects of plumes on
weather, climate, and air quality. Plume age, the age of smoke furthest
down-plume, is lognormally distributed with a median of 2.8 h (25th and 75th
percentiles at 1.3 h and 4.0 h), different from the median ages reported in
other studies. Intercomparison of our results with previous studies shows
that the shape, height, optical depth, and lifetime characteristics reported
for tropical biomass burning plumes on three continents are dissimilar and
distinct from the same characteristics of non-tropical wildfire plumes. |
| |
|
| Teil von |
|
|
|
|
|
|
|
|