Radiative Effect of Springtime Biomass-Burning Aerosols over Northern Indochina during 7-SEAS/BASELInE 2013 Campaign

Shantanu Kumar Pani,Sheng-Hsiang Wang,Ta-Chih Hsiao,Chung-Te Lee,Ming-Tung Chuang,Brent N Holben,Si-Chee Tsay,Serm Janjai,Neng-Huei Lin,Somporn Chantara

doi:10.4209/aaqr.2016.03.0130

Shantanu Kumar Pani, Sheng-Hsiang Wang + Show 8 more

Open Access

https://doi.org/10.4209/aaqr.2016.03.0130

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Abstract

The direct aerosol radiative effects of biomass-burning (BB) aerosols over northern Indochina were estimated by using aerosol properties (physical, chemical, and optical) along with the vertical profile measurements from ground-based measurements with integration of an optical and a radiative transfer model during the Seven South East Asian Studies Biomass-Burning Aerosols Stratocumulus Environment: Lifecycles Interactions Experiment (7-SEASBASELInE) conducted in spring 2013. Cluster analysis of backward trajectories showed the air masses arriving at mountainous background site (Doi Ang Khang; 19.93degN, 99.05degE, 1536 m above mean sea level) in northern Indochina, mainly from near-source inland BB activities and being confined in the planetary boundary layer. The PM(sub10) and black carbon (BC)mass were 87 +/- 28 and 7 +/- 2 micrograms m(exp -3), respectively. The aerosol optical depth (AOD (sub 500) was found to be 0.26--1.13 (0.71 +/- 0.24). Finer (fine mode fraction is approximately or equal to 0.95, angstrom-exponent at 440-870 nm is approximately or equal to 1.77) and significantly absorbing aerosols(single scattering albedo is approximately or equal to 0.89, asymmetry-parameter is approximately or equal to 0.67, and absorption AOD 0.1 at 440 nm) dominated over this region. BB aerosols (water soluble and BC) were the main contributor to the aerosol radiative forcing (ARF), while others (water insoluble, sea salt and mineral dust) were negligible mainly due to their low extinction efficiency. BC contributed only 6 to the surface aerosol mass but its contribution to AOD was 12 (2 times higher). The overall mean ARF was 8.0 and -31.4 W m(exp -2) at top-of-atmosphere (TOA) and at the surface (SFC), respectively. Likely, ARF due to BC was +10.7 and -18.1 W m(exp -2) at TOA and SFC, respectively. BC imposed the heating rate of +1.4 K d(exp -1) within the atmosphere and highlighting its pivotal role in modifying the radiation budget. We propose that to upgrade our knowledge on BB aerosol radiative effects in BB source region, the long-term and extensive field measurements are needed.

Highlights

Biomass-burning (BB) aerosols are the significant contributor to the global aerosol loading and radiation budgets (Crutzen and Andreae, 1990; Penner et al, 1992)
We propose that to upgrade our knowledge on BB aerosol radiative effects in BB source region, the long-term and extensive field measurements are needed
There were a few campaigns conducted to investigate the characteristics of regional BB emitted aerosols and their climatic effect, such as Southern African Regional Science Initiative (SAFARI) (Andreae et al, 1996), Smoke, Clouds and Radiation-Brazil (SCAR-B) (Kaufman et al, 1998), Indian Ocean Experiment (INDOEX) (Ramanathan et al, 2001), Transport and Chemical Evolution over the Pacific (TRACE-P) (Jacob et al, 2003), and Biomass Burning Aerosols in Southeast Asia: Smoke Impact Assessment (BASE-ASIA) (Tsay et al, 2013)

Summary

Introduction

Biomass-burning (BB) aerosols are the significant contributor to the global aerosol loading and radiation budgets (Crutzen and Andreae, 1990; Penner et al, 1992). There were a few campaigns conducted to investigate the characteristics of regional BB emitted aerosols and their climatic effect, such as Southern African Regional Science Initiative (SAFARI) (Andreae et al, 1996), Smoke, Clouds and Radiation-Brazil (SCAR-B) (Kaufman et al, 1998), Indian Ocean Experiment (INDOEX) (Ramanathan et al, 2001), Transport and Chemical Evolution over the Pacific (TRACE-P) (Jacob et al, 2003), and Biomass Burning Aerosols in Southeast Asia: Smoke Impact Assessment (BASE-ASIA) (Tsay et al, 2013). Pani et al (2016a) reported the enhancement of surface cooling and free troposphere warming by the transported Indochina BB plumes over the northern South China Sea during the Seven South East Asian Studies (7SEAS)/Dongsha Experiment

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