Evaluating Spatial and Temporal Variations of Aerosol Optical Depth and Biomass Burning over Southeast Asia Based on Satellite Data Products

Chih-Hua Chang,Yu-Li Hsiao,Charnsmorn Hwang

doi:10.4209/aaqr.2015.10.0589

Abstract

Many severe air quality problems in the major cities of Southeast Asia (SEA) are related to atmospheric aerosols, and these are mainly caused by smoke haze from biomass burning. To better understand the cause and effect relationships for the tempo-spatial distributions of atmospheric aerosols in SEA, a variety of satellite-based Moderate Resolution Imaging Spectroradiometer (MODIS) products of aerosol optical depth (AOD), precipitation, burned area (BA) and fire pixel counts (FC, derived from the active fire product) were collected and processed to evaluate the spatial and temporal variations among atmospheric aerosol, climate factors, and biomass burning in SEA during 2002–2011. High AOD zones (HAZs) located in the continental and maritime portion of SEA are identified through hotspot analysis of AOD maps. The peak AOD, BA and FC months are concentrated in the dry seasons of each HAZ. Although BA and FC are mostly identified in Indochina, the HAZ located in maritime SEA has a comparable level of AOD which may be contributed by the fire-related emissions from peatland in Indonesia. Compared to the commonly used fire-effected area dataset (MCD45 product), BA derived from a hybrid approach (MCD64 product) that considers both active fire (AF) and land change information has higher correlation coefficients with AOD in both HAZs. Linear regression models are then developed for the Indochina and the maritime HAZs, to estimate the level of AOD from the MODIS monthly fire datasets. In general the empirical models can better explain the temporal trends of AOD in HAZs by using AF-based products. The links between regional aerosol and local burning in Indochina SEA are relatively complex due to the cross-boundary transport of aerosol from Southern China.

Highlights

Biomass burning in tropical Asia emits large amounts of gaseous pollutants and particulate matter, which play an important role in global climate change (Seiler and Crutzen, 1980), and have caused considerable concerns with regard to regional air quality (Marlier et al, 2015)
burned area (BA) and fire pixel counts (FCs) are mostly identified in Indochina, the High AOD zones (HAZs) located in maritime Southeast Asia (SEA) has a comparable level of aerosol optical depth (AOD) which may be contributed by the fire-related emissions from peatland in Indonesia
The high AOD region in Indochina is approximately located in the northern Indochina Peninsula during January to April (Figs. 2(a)–2(d)); and that in the maritime SEA is located at Kalimantan (Indonesia), during August to October (Figs. 2(h)–2(j))

Summary

Introduction

Biomass burning in tropical Asia emits large amounts of gaseous pollutants and particulate matter, which play an important role in global climate change (Seiler and Crutzen, 1980), and have caused considerable concerns with regard to regional air quality (Marlier et al, 2015). AOD data produced from the Moderate resolution Imaging Spectroradiometer (MODIS, on board the NASA platform Terra and Aqua) has been widely applied to examine the seasonal and regional variability of trace gases and aerosol particles (Alpert et al, 2012; Indira et al, 2013; Lalitaporn et al, 2013; Zheng et al, 2013; Mehta, 2015), and to evaluate its relation to air pollution (Zhu et al, 2011) or significant emission sources, such as burning activities (Koren et al, 2007; Bevan et al, 2009; Vadrevu et al, 2011). In view of the important impacts on global climate and regional air quality, the scientific community has developed a number of operational fire products based on the detection of thermal anomalies (i.e., active fires, abbreviated to AF) and land surface changes (i.e., burned areas, abbreviated to BA). Our knowledge about the spatial and temporal distributions of fire sources and aerosols has been extended with the increased application of satellitebased observations, and this has encouraged the scientific community to make more efforts to improving the products by continuously updating the retrieval algorithms and collecting reliable field data for validation

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