Biomass burning aerosols and the low-visibility events in Southeast Asia
Fires including peatland burning in Southeast Asia have become a major concern to the general public as well as governments in the region. This is because aerosols emitted from such fires can cause persistent haze events under certain weather conditions in downwind locations, degrading visibility an...
Main Authors: | , , |
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Format: | Article |
Language: | English |
Published: |
Copernicus Publications
2017-01-01
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Series: | Atmospheric Chemistry and Physics |
Online Access: | http://www.atmos-chem-phys.net/17/965/2017/acp-17-965-2017.pdf |
Summary: | Fires including peatland burning in Southeast Asia have become a major
concern to the general public as well as governments in the region. This is
because aerosols emitted from such fires can cause persistent haze events
under certain weather conditions in downwind locations, degrading visibility
and causing human health issues. In order to improve our understanding of the
spatiotemporal coverage and influence of biomass burning aerosols in
Southeast Asia, we have used surface visibility and particulate matter
concentration observations, supplemented by decade-long (2003 to 2014)
simulations using the Weather Research and Forecasting (WRF) model with a
fire aerosol module, driven by high-resolution biomass burning emission
inventories. We find that in the past decade, fire aerosols are responsible
for nearly all events with very low visibility (< 7 km). Fire
aerosols alone are also responsible for a substantial fraction of low-visibility events (visibility < 10 km) in the major metropolitan
areas of Southeast Asia: up to 39 % in Bangkok, 36 % in Kuala Lumpur, and
34 % in Singapore. Biomass burning in mainland Southeast Asia accounts for
the largest contribution to total fire-produced PM<sub>2.5</sub> in Bangkok
(99 %), while biomass burning in Sumatra is a major contributor to
fire-produced PM<sub>2.5</sub> in Kuala Lumpur (50 %) and Singapore (41 %).
To examine the general situation across the region, we have further defined
and derived a new integrated metric for 50 cities of the Association of
Southeast Asian Nations (ASEAN): the haze exposure day (HED), which measures
the annual exposure days of these cities to low visibility (< 10 km)
caused by particulate matter pollution. It is shown that HEDs have increased
steadily in the past decade across cities with both high and low populations.
Fire events alone are found to be responsible for up to about half of the
total HEDs. Our results suggest that in order to improve the overall air
quality in Southeast Asia, mitigation policies targeting both biomass burning
and fossil fuel burning sources need to be implemented. |
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ISSN: | 1680-7316 1680-7324 |