Observations of Aerosol Optical Properties over 15 AERONET Sites in Southeast Asia

Tuesday, 16 December 2014: 9:30 AM
Justin Dale Chan1, Nofel Lagrosas2, Sherdon Niño Uy3, Brent N Holben4, Susana Dorado5, Victorino Tobias Jr.5, Nguyen Xuan Anh6, Lin Po-Hsiung7, Serm Janjai8, Santo V Salinas Cortijo9, Soo Chin Liew9, Hwee San Lim10 and Puji Lestari11, (1)Ateneo de Manila University, Quezon City, Philippines, (2)Ateneo de Manila University, Manila Observatory, Quezon City, Philippines, (3)Manila Observatory, Quezon City, Philippines, (4)NASA Goddard Space Flight Center, Greenbelt, MD, United States, (5)Notre Dame of Marbel University, Koronadal, Philippines, (6)VietNam Academy of Science and Technology, Hanoi, Vietnam, (7)NTU National Taiwan University, Taipei, Taiwan, (8)Silpakorn University, Nokorn Pathom, Thailand, (9)National University of Singapore, Singapore, Singapore, (10)University Sains Malaysia, Penang, Malaysia, (11)Institute of Technology Bandung, Bandung, Indonesia
Mean column-integrated optical properties from ground sun photometers of the Aerosol Robotic Network (AERONET) are studied to provide an overview of the characteristics of aerosols over the region as part of the 7 Southeast Asian Studies (7-SEAS) mission. The 15 AERONET sites with the most available level 2 data products are selected from Thailand (Chiang Mai, Mukdahan, Songkhla and Silpakorn University), Malaysia (University Sains Malaysia), Laos (Vientiane), Vietnam (Bac Giang, Bac Lieu and Nha Trang), Taiwan (National Cheng Kung University and Central Weather Bureau Taipei), Singapore, Indonesia (Bandung) and the Philippines (Manila Observatory and Notre Dame of Marbel University). For all 15 sites, high angstrom exponent values (α>1) have been observed. Chiang Mai and USM have the highest mean Angstrom exponent indicating the dominance of fine particles that can be ascribed to biomass burning and urbanization. Sites with the lowest Angstrom exponent values include Bac Lieu (α=1.047) and Manila Observatory (α=1.021). From the average lognormal size distribution curves, Songkhla and NDMU show the smallest annual variation in the fine mode region, indicating the observed fine aerosols are local to the sites. The rest of the sites show high variation which could be due to large scale forcings (e.g., monsoons and biomass burnings) that affect aerosol properties in these sites. Both high and low single scattering albedo at 440 nm (ω0440) values are found in sites located in major urban areas. Silpakorn University, Manila Observatory and Vientiane have all mean ω0440 < 0.90. Singapore and CWB Taipei have ω0440 > 0.94. The discrepancy in ω0 suggests different types of major emission sources present in urban areas. The absorptivity of urban aerosols can vary depending on the strength of traffic emissions, types of fuel combusted and automobile engines used, and the effect of biomass burning aerosols during the dry season. High aerosol optical depth values (τa550 > 0.4) are mainly found over inland sites north of Songkhla and south of China on mainland Asia. Major pollution types in the region include biomass burning smoke and urban aerosols. The highest average τa550 is measured in Bac Giang, which has been studied to be greatly affected by aerosol sources from Eastern China during the later parts of the year.