Investigation of the CCN Activity, BC and UVBC Mass Concentrations of Biomass Burning Aerosols during the 2013 BASELInE Campaign

Abstract

Biomass-burning (BB) aerosols, acting as cloud condensation nuclei (CCN), can influence cloud microphysical and radiative properties. In this study, we present CCN measured near the BB source regions over northern Southeast Asia (Doi Ang Khang, Thailand) and at downwind receptor areas (Lulin Atmospheric Background Station, Taiwan), focusing exclusively on 13-20 March 2013 as part of 2013 spring campaign of the Seven SouthEast Asian Studies (7-SEAS) intensive observation. One of the campaign's objectives is to characterize BB aerosols serving as CCN in SouthEast Asia (SEA). CCN concentrations were measured by a CCN counter at 5 supersaturation (SS) levels: 0.15%, 0.30%, 0.45%, 0.60%, and 0.75%. In addition, PM 2.5 and black carbon mass concentrations were analyzed by using a tapered element oscillating microbalance and an aethalometer. It was found the number-size distributions and the characteristics of hygroscopicity (e.g., activation ratio and κ) of BB aerosols in SEA have a strong diurnal pattern, and different behaviors of patterns were characterized under two distinct weather systems. The overall average κ value was low (0.05-0.1) but comparable with previous CCN studies in other BB source regions. Furthermore, a large fraction of UV-absorbing organic material (UVBC) and high Delta-C among BB aerosols were also observed, which suggest the existence of substantial particulate organic matter in fresh BB aerosols. These data provide the most extensive characterization of BB aerosols in SEA until now.

Satellite-Surface Perspectives of Air Quality and Aerosol-Cloud Effects on the Environment: An Overview of 7-SEAS/BASELInE

“…These approaches provide useful metrics for constraining the CCN activity in, for example, cloudresolving models, which may help clarify the connections between aerosol hygroscopicity and cloud-radiationprecipitation interactions. During the 2013 BASELInE campaign at DAK, Hsiao et al (2016) reported that the values of κ-parameter were low (0.05-0.1) and correlate well with the amount of particulate organic matter. These observations were comparable with those of κ-parameter estimated from H-TDMA measurements (κ ~0.07-0.08) in the Amazonia (Rissler et al, 2004(Rissler et al, , 2006, as well as consistent with previous studies on water uptake of carbon-dominated aerosols (e.g., Petters et al, 2009;Carrico et al, 2010;Dusek et al, 2011;Engelhart et al, 2012).…”

Tracer-based investigation of organic aerosols in marine atmospheres from marginal seas of China to the northwest Pacific Ocean

“…BVOCs consist primarily of isoprene, monoterpenes, sesquiterpenes and their oxygenated hydrocarbons, such as alcohols, aldehydes and ketones (Ehn et al, 2014;, and account for the majority of the global VOC inventory (Heald et al, 2008;Zhu et al, 2016a, b). However, emission fluxes and oxidation processes of BVOCs show great variation, depending on global warming and other factors such as regional landscape and other pollutants in the ambient air (Ait-Helal et al, 2014;Claeys et al, 2004;Hu and Yu, 2013;Peñuelas and Staudt, 2010). Unlike a potential increase in BVOC-derived organics aerosols in marine atmospheres under global warming, anthropogenic VOCs and carbonaceous particles over the continents have decreased due to effective mitigation of air pollutants over the last few decades Murphy et al, 2011;Sharma et al, 2004;.…”

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

“…BB activities in the form of wildland forest fires and agricultural burning are very pronounced in the northern Indochina regions mainly during dry/spring season from late February to mid-April (i.e., Gautam et al, 2013;Hsiao et al, 2016). Aerosol concentrations during this season are typically at peak associated with BB activity and contribute significantly to the regional emissions (Carmichael et al, 2003;Janjai et al, 2009;Streets et al, 2009).…”

“…The impact of BB on air quality over Southeast Asia was evaluated within the framework of BASE-ASIA campaign by using chemical transport modelling (Fu et al, 2012;Huang et al, 2013). Moreover, some recent studies also emphasized the BB emissions from Indochina region and explained their impact on regional air quality, atmospheric radiation, hydrological cycle, and climate (e.g., Lin et al, 2013;Tsay et al, 2013;Lin et al, 2014;Tsay et al, 2016) by using in-situ measurements (e.g., Chuang et al, 2013b;Wang et al, 2015;Chuang et al, 2016;Hsiao et al, 2016;Khamkaew et al, 2016;Pantina et al, 2016;Sayer et al, 2016), satellite observations (e.g., Hsu et al, 2003;Huang et al, 2011;Campbell et al, 2013;Lee et al, 2016b), remote sensing Reid et al, 2013), and modeling studies (Fu et al, 2012;Loftus et al, 2016) within the 7-SEAS framework. Wang et al (2015) investigated the presence of strongly absorbing (single-scattering albedo ≈0.88 and absorption angstrom exponent ≈1.5) carbonaceous aerosols within the planetary boundary layer (PBL) over northern Indochina in 2014 spring.…”