Estimating Surface PM2.5 Concentrations and Chemical Composition from High Spectral Resolution Lidar Retrievals Using the HSRL-CH Methodology
Bethany Sutherland, NICHOLAS MESKHIDZE, North Carolina State University
Abstract Number: 422
Working Group: Coast to Coast Campaigns on Aerosols, Clouds, Chemistry, and Air Quality
Abstract
Remote monitoring of surface concentrations of particles with an aerodynamic diameter under 2.5 μm (PM2.5) remains challenging as the hygroscopic growth and the resulting optical properties of aerosols depend on their chemical composition. High Spectral Resolution Lidar (HSRL) retrievals of aerosol intrinsic properties can be used to assign aerosol types (e.g., urban, smoke, fresh smoke, dusty mix, maritime, and polluted maritime). These HSRL-derived aerosol types can then be linked to likely chemical speciation using the GEOS-Chem model-based CATCH (Creating Aerosol Types from Chemistry) algorithm, developed in our research group.
Here we examine a recently developed HSRL-CH method to estimate surface PM2.5 by leveraging HSRL-retrieved extinction and assigned aerosol types in combination with the GEOS-Chem/CATCH-derived aerosol type-specific chemical compositions. The data were acquired from 99 research flights conducted during the ACEPOL, SEAC4RS, DISCOVER-AQ California, DISCOVER-AQ Colorado, and DISCOVER-AQ Texas field campaigns. HSLR-CH derived concentrations and speciation are compared to hourly PM2.5 concentrations and daily chemical compositions measured at U.S. EPA Air Quality System (AQS) sites. Generally, results using HSRL-CH compare favorably with the ground measurements-consistent with previously published results using DISCOVER-AQ BWC retrievals. The extension to include retrievals from five additional campaigns highlights the conditions best suited for success remotely deriving PM2.5 using HSRL-CH, and several remaining challenges (e.g. cases of low mixing layer height or complex local meteorology). This analysis provides new insights into the suitability of GEOS-Chem/CATCH derived aerosol type-specific compositions for remotely deriving PM2.5. Comparisons of HSRL-CH-derived chemical compositions with AQS speciation for each aerosol type will also be presented.