Light absorption properties of brown carbon over the western Pacific region

Abstract

<p>Brown carbon (BrC) is generally emitted during coal combustion, biomass burning, and the formation of secondary organic aerosols. BrC is an exceptional type of organic compound that absorbs the incoming solar radiation efficiently at near-ultraviolet wavelengths and can influence the direct radiative forcing estimates. Lulin Atmospheric Background Station (LABS, 23.47°N, 120.87°E; 2862 m above sea level) on the summit of Lulin Mountain in central Taiwan is the only high-altitude background station in the western Pacific region to study the impact of various long-range transported air pollutants. LABS usually receives the westerly winds coupled with biomass-burning emissions from peninsular Southeast Asia during the springtime. Aerosol measurements are carried out at LABS as a part of the Seven South East Asian Studies/Biomass-burning Aerosols & Stratocumulus Environment: Lifecycles & Interactions Experiment (7-SEAS/BASELInE) 2013 spring campaign. Light absorption coefficients are measured by the Aethalometer (AE 31, Magee Scientific, USA). Assuming a negligible contribution from dust, absorption solely due to BrC is estimated by subtracting the absorption of black carbon (BC) from total absorption. The relationships between BrC light absorption and carbonaceous fractions are investigated during the sampling period. The atmospheric radiative forcing due to BrC over the western Pacific region accounts for approximately 30% of that from BC. The detailed results will be presented.</p>