Using satellite data to investigate aerosol decay patterns downwind: implications for aerosol formation and removal processes
Abstract
Atmospheric aerosols are affected by physical and chemical processes, including primary emissions, secondary formations, and dry and wet removals, all of which combine to set the aerosol lifetime. The near-source spatial pattern of aerosol abundance can be inferred from the aerosol optical depth (AOD) from satellite remote sensing. These patterns contain information about aerosol lifetime that has not been extensively explored.
We use multi-year and seasonally averaged observations of the Multi-Angle Implementation of Atmospheric Correction (MAIAC) product to investigate the downwind decay pattern of AOD near major urban areas in the United States and other locations. After segregating the AOD observations into different wind directions based on wind fields from the ERA5 reanalysis, an exponential decay pattern was revealed. By analogy to research on the lifetime of NOx, we use Exponentially Modified Gaussian (EMG) fitting to estimate the e-folding lifetime of AOD around each city. Fitted lifetimes vary from 1 to 40 hours, substantially smaller than the global averaged aerosol lifetime of 3-7 days in models, reflecting rapid aerosol production and removal in the boundary layer. Over the same city, AOD tends to be more localized in winter, and the fitted lifetime is usually longer in summer. This slower decay of AOD in summer reflect the stronger downwind secondary aerosol formation from precursor gases. Future work will examine and interpret AOD decay and lifetime over other regions and explore trends in aerosol lifetime.- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.A11S2813L
- Keywords:
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- 0365 Troposphere: composition and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 0368 Troposphere: constituent transport and chemistry;
- ATMOSPHERIC COMPOSITION AND STRUCTURE;
- 3307 Boundary layer processes;
- ATMOSPHERIC PROCESSES;
- 3323 Large eddy simulation;
- ATMOSPHERIC PROCESSES