Research

Dust morphology and its impact on the aerosol optics, reactive uptake of trace gases and UV-Vis trace gas retrievals

Mineral dust is often treated as spherical in chemical transport and trace gas retrieval models. We investigate how dust shape affects gas-particle and radiation-particle interactions. We examine the impact of dust shape on optical properties and trace gas retrievals at ultraviolet and visible wavelengths. We find that treating dust as nonspherical in trace gas retrievals of nitrogen dioxide decreases the retrieval sensitivity to dust. We also examine the impact of dust shape on heterogeneous chemistry by developing and applying a theoretical model. We find that dust pores change particle surface area significantly and subsequently, reaction and diffusion parameters. Overall, this study signifies the importance of accounting for nonsphericity in chemical transport and trace gas retrieval models.

Fire plume height and it’s impact on the surface PM2.5 inferred from satellite AOD

Wildfires can inject smoke at high altitude in the atmosphere. The resulting free tropospheric aerosols may affect inference of ground-level fine particulate matter (PM2.5) from satellite retrievals of columnar aerosol optical depth (AOD). In this study, we include a plume height parameterization (GFAS) in the chemical transport model GEOS-Chem to examine its effect on the simulated AOD to PM2.5 relationship during extreme wildfire events over the US and Canada in 2018 and 2020. We scale the GFAS plume height in GEOS-Chem to represent satellite retrievals of plume height (EPIC). We find that replacing default wildfire emissions from GFED at the surface with the scaled GFAS plume height in GEOS-Chem reduces the bias of measured PM2.5 versus PM2.5 inferred from MAIAC satellite AOD for 2018 (slope decreases from 2.59 to 1.09) and for 2020 (slope decreases from 2.66 to 1.16). Replacing GFED surface emission with GFAS plume height also improves the simulated AOD versus sun photometer observations from AERONET in 2018 (slope increases from 0.31 to 0.99, r^2 increases from 0.36 to 0.54) and 2020 (slope increases from 0.21 to 0.80, and r^2 increases from 0.34 to 0.78). Overall, this study signifies the importance of incorporating plume height information for inference of PM2.5 from satellite AOD during extreme wildfire events.