Determination of Lidar Ratio for Major Aerosol Types over Western North Pacific Based on Long-Term MPLNET Data

• Published in: Remote Sensing
• Main Authors: Sheng-Hsiang Wang, Heng-Wai Lei, Shantanu Kumar Pani, Hsiang-Yu Huang, Neng-Huei Lin, Ellsworth J. Welton, Shuenn-Chin Chang, Yueh-Chen Wang
• Format: Article in Journal/Newspaper
• Language: English
• Published: MDPI AG 2020
• Subjects: ground based remote sensing; aerosols optical properties; lidar ratio; aerosol type; Science; Q; Pacific; Aerosol Robotic Network
• Online Access: https://doi.org/10.3390/rs12172769; https://doaj.org/article/976242c2c5474b8d864b1a400de9fbd3

East Asia is the most complex region in the world for aerosol studies, as it encounters a lot of varieties of aerosols, and aerosol classification can be a challenge in this region. In the present study, we focused on the relationship between aerosol types and aerosol optical properties. We analyzed the long-term (2005–2012) data of vertical profiles of aerosol extinction coefficients, lidar ratio ( S p ), and other aerosol optical properties obtained from a NASA Micro-Pulse Lidar Network and Aerosol Robotic Network site in northern Taiwan, which frequently receives Asian continental outflows. Based on aerosol extinction vertical profiles, the profiles were classified into two types: type 1 (single-layer structure) and type 2 (two-layer structure). Fall season (October–November) was the prevailing season for the Type 1, whereas type 2 mainly happened in spring (March–April). In type 1, air masses normally originated from three regional sectors, i.e., Asia continental (AC), Pacific Ocean (PO), and Southeast Asia (SA). The mean S p values were 39 ± 17 sr, 30 ± 12 sr, and 38 ± 18 sr for the AC, PO, and SA sectors, respectively. The S p results suggested that aerosols from the AC sector contained dust and anthropogenic particles, and aerosols from the PO sector were most likely sea salts. We further combined the EPA dust event database and backward trajectory analysis for type 2. Results showed that S p was 41 ± 14 sr and 53 ± 21 sr for dust storm and biomass-burning events, respectively. The S p for biomass-burning events in type 2 showed two peaks patterns. The first peak occurred within range of 30–50 sr corresponding to urban pollutant, and the second peak occurred within range of 60–80 sr in relation to biomass burning. Finally, our study summarized the S p values for four major aerosol types over northern Taiwan, viz., urban (42 ± 18 sr), dust (34 ± 6 sr), biomass-burning (69 ± 12 sr), and oceanic (30 ± 12 sr). Our findings provide useful references for aerosol classification and air pollution identification ...