Long-Term Trends in Aerosol Optical Properties and Biomass Burning Influence at the Southern Great Plains

MANISHA MEHRA, Yang Wang, Sujan Shrestha, Arthur J. Sedlacek, Yan Feng, Janek Uin, University of Miami

     Abstract Number: 282
     Working Group: Aerosols, Clouds and Climate

Abstract
Direct aerosol radiative forcing estimates depend on key aerosol optical properties (AOPs), including the scattering coefficient (σsp), absorption coefficient (σap), and single scattering albedo (ωo). Despite their importance for constraining radiative impacts and source contributions, long-term observations of these properties remain limited. Building on an earlier study at the U.S. Department of Energy’s Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site (Sheridan et al., 2001), this study analyzes multi-year AOP trends from January 2018 to December 2024. The median σsp at 550 nm was 15.4 Mm⁻¹, less than half the value reported in 1996–2000, potentially reflecting reductions in particulate matter emissions due to implementation of cleaner technologies over recent decades. The median σap was ~1.2 Mm⁻¹, highest during late spring and autumn, consistent with earlier reported seasonal patterns. The median ωo decreased from 0.95 (1996 to 2000) to 0.92 (2018 and 2024), with further decrease to ~0.87 in late spring and autumn, indicating increased aerosol absorption during these seasons. This seasonal decrease in ωo, along with elevated σap, indicates the influence of regional or local biomass burning (BB) emissions. The median aerosol absorption exponent (AAE) was 0.98, suggesting dominant fossil fuel combustion sources, while elevated AAE values (1.1–1.4) in spring and autumn point to contributions from BB-derived brown carbon. Together, these results highlight both persistent seasonal features and evolving AOPs over two decades at SGP, reinforcing the potential utility of AOPs as indicators of BB influence. Previous studies have demonstrated the effectiveness of AOPs for real-time BB characterization, even under polluted conditions influenced by dilute BB plumes. Therefore, this study further investigates the efficiency of AOPs for BB characterization at SGP. The detailed results of the frequency and seasonality of BB influence at SGP will be presented at the conference.