Characterization of atmospheric brown carbon

Atmospheric organic matter that absorbs ultraviolet and visible radiation (“brown carbon” or BrC) can affect the Earth’s radiative energy balance and affect local photochemistry. Measurements in the laboratory and field are conducted to address critical knowledge gaps regarding their sources, sinks, and optical properties.

Figure 1: Evolution of mass absorption coefficient (MAC) for UVB photolysis (blue circles) and aqueous OH oxidation (green triangles) as a function of UVB light illumination. From Wong et al., Atmos. Chem. Phys., doi:10.5194/acp-19-7319-2019, 2019.
Figure 2: Estimate of raditive forcing contributions due to brown carbon (BrC) and black carbon (BC) as a function of altitude estimated from aircract observations over the continental United States. BrC’s impact is greatest at high altitude, where climate sensitivity to absorbing aerosols increases relative to ground level, From Zhang et al., Nat. Geosci., doi:10.1038/ngeo2960, 2017.

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