Haze in Singapore – source attribution of biomass burning PM&amp;lt;sub&amp;gt;10&amp;lt;/sub&amp;gt; from Southeast Asia

Ayoe Buus Hansen,Shao-Yi Lee,Matthew Craig Hort,Emma Kendall,Boon Ning Chew,Claire Suzanne Witham,Christopher Gan,Wei Ming Chong

doi:10.5194/acp-19-5363-2019

Abstract

Abstract. This paper presents a study of haze in Singapore caused by biomass burning in Southeast Asia over the 6-year period from 2010 to 2015, using the Numerical Atmospheric-dispersion Modelling Environment (NAME), which is a Lagrangian dispersion model. The major contributing source regions to the haze are identified using forwards and backwards model simulations of particulate matter. The coincidence of relatively strong southeast monsoonal winds with increased biomass burning activities in the Maritime Continent create the main Singapore haze season from August to October (ASO), which brings particulate matter from varying source regions to Singapore. Five regions are identified as the dominating sources of pollution during recent haze seasons: Riau, Peninsular Malaysia, South Sumatra, and Central and West Kalimantan. In contrast, off-season haze episodes in Singapore are characterised by unusual weather conditions, ideal for biomass burning, and contributions dominated by a single source region (different for each event). The two most recent off-season haze events in mid-2013 and early 2014 have different source regions, which differ from the major contributing source regions for the haze season. These results challenge the current popular assumption that haze in Singapore is dominated by emissions/burning from only Indonesia. For example, it is shown that Peninsular Malaysia is a large source for the Maritime Continent off-season biomass burning impact on Singapore. The results demonstrate that haze in Singapore varies across year, season, and location and is influenced by local and regional weather, climate, and regional burning. Differences in haze concentrations and variation in the relative contributions from the various source regions are seen between monitoring stations across Singapore, on a seasonal as well as on an inter-annual timescale. This study shows that even across small scales, such as in Singapore, variation in local meteorology can impact concentrations of particulate matter significantly, and it emphasises the importance of the scale of modelling both spatially and temporally.

Highlights

Haze caused by biomass burning is a significant issue throughout Southeast Asia
Using hourly PM10 observations we evaluate our model output before using the results to address the research questions posed in Sect
In this study we have used the atmospheric dispersion model, Numerical Atmospheric-dispersion Modelling Environment (NAME), to attribute PM10 concentrations in Singapore caused by biomass burning to their source region

Summary

Introduction

Haze caused by biomass burning is a significant issue throughout Southeast Asia. Clearing forest for plantations by burning is a quick and easy way to open up and fertilise the soil; it is a process that is difficult to control. The emissions from these fires can have massive and detrimental impacts far from where the original fires were lit. It is an ancient practice as well as a natural process which modifies the Earth’s surface (Pereira et al, 2016). Over recent decades the impacts of biomass burning have been felt in increasing degree in Southeast Asia and in Singapore (Oozeer et al, 2016)

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Conclusion