Journal cover Journal topic
Atmospheric Chemistry and Physics An interactive open-access journal of the European Geosciences Union
Atmos. Chem. Phys., 17, 965-980, 2017
http://www.atmos-chem-phys.net/17/965/2017/
doi:10.5194/acp-17-965-2017
© Author(s) 2017. This work is distributed
under the Creative Commons Attribution 3.0 License.
Research article
23 Jan 2017
Biomass burning aerosols and the low-visibility events in Southeast Asia
Hsiang-He Lee1, Rotem Z. Bar-Or2, and Chien Wang1,2 1Center for Environmental Sensing and Modeling, Singapore-MIT Alliance for Research and Technology, Singapore
2Center for Global Change Science, Massachusetts Institute of Technology, Cambridge, MA, USA
Abstract. 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 PM2.5 in Bangkok (99 %), while biomass burning in Sumatra is a major contributor to fire-produced PM2.5 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.

Citation: Lee, H.-H., Bar-Or, R. Z., and Wang, C.: Biomass burning aerosols and the low-visibility events in Southeast Asia, Atmos. Chem. Phys., 17, 965-980, doi:10.5194/acp-17-965-2017, 2017.
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Short summary
Fires including peatland burning in Southeast Asia (SA) have become a major concern in the region. In order to improve our understanding of the spatiotemporal coverage and influence of fire aerosols in SA, we have used surface visibility and aerosol observations, added by decade-long simulations using the WRF model with a fire aerosol module. Our result suggests that mitigation policies targeting both biomass burning and fossil fuel burning sources need to be implemented.
Fires including peatland burning in Southeast Asia (SA) have become a major concern in the...
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