An Innovative Approach for Deriving CALIOP-Based Particulate Matter Concentrations Through a Bulk-Mass-Modeling-Based Method

Particulate matter (PM), especially PM with particle sizes less than 2.5 µm (PM_2.5), significantly reduces air quality and negatively impacts human health. Previous studies concerning this topic have relied heavily on correlative relationships between passive satellite-derived aerosol optical depth and near-surface PM_2.5, but are limited by the column-integrated perspective of passive sensors. Different from these approaches, for the first time, we demonstrate a bulk-mass-modeling-based method for deriving PM concentrations for the contiguous United States using two years (2008-2009) of NASA Cloud-Aerosol Lidar with Orthogonal Polarization (CALIOP) measurements. Daytime and nighttime analyses are conducted using near-surface CALIOP aerosol extinction retrievals, bulk mass extinction efficiencies, and model-based hygroscopicity. Initial results are highlighted, and reveal that nighttime CALIOP-derived PM_2.5 agrees reasonably well with ground-based PM_2.5 observations from the U.S. Environmental Protection Agency (less so for daytime conditions), implying this method exhibits some merit in monitoring PM_2.5 concentrations using CALIOP data. Results from various sensitivity studies are also reported, including those of cloudiness and assumptions regarding surface layer height and aerosol type. Lastly, a preliminary analysis for e-folding correlation length of surface PM_2.5 indicates that CALIOP observations, although spatially limited, may still be useful for PM_2.5 studies.