Seminar

Absorbing trace gases and aerosols: Recent laboratory and field work on glyoxal and brown carbon

Speaker: Rebecca Washenfelder, NOAA ESRL & CU CIRES

When: Wednesday, March 6, 2013, 3:30 p.m. Mountain Time
Location: Room 2A305, DSRC (NOAA Building), 325 Broadway, Boulder
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Abstract:

Recent advances in optical spectroscopy have led to new broadband cavity enhanced spectrometers (BBCES) that combine high-finesse optical cavities with high-powered LED light sources, spectrally resolving the light output with a grating spectrometer. This technique can be used to make sensitive, in situ measurements of optical extinction. Organic compounds contribute a large fraction of aerosol mass, and glyoxal has been identified in previous laboratory and field studies to be one potential source of organic mass. We deployed a BBCES instrument to measure glyoxal during summer 2010 in Pasadena, California. We used three methods to quantify the contribution of glyoxal to aerosol in Los Angeles, and found that it accounts for only 0 - 4% of the secondary organic aerosol mass. Quantifying the optical properties of aerosols is important to understand their role in the Earth’s radiative budget. Previous measurements have indicated that brown carbon aerosol has a wavelength-dependent absorption that increases in the ultraviolet spectral region, and recent modeling suggests that this is an important component of aerosol radiative forcing. We have conducted recent laboratory and field measurements of aerosol scattering and absorption in the ultraviolet spectral region to address these issues.