33: Light Absorption Enhancement in Coated Atmospheric Tar Balls Using Mie Theory

Music City Center 

Atmospheric tar balls (TBs) are solid, strong light-absorbing organic particles emitted through wildfires. TBs can disrupt Earth's energy balance by absorbing incoming solar radiation. However, there are still large uncertainties with TBs' optical properties. Moreover, when TBs have different coatings (e.g., water and organic), their light absorption properties will be enhanced. This highly variable optical property and light enhancement of TBs are not included in a climate model.

This study applies Mie calculations to investigate the light absorption enhancement of different coatings on TBs. We used different optical properties of TBs in the literature to cover the variable optical properties of TBs by testing the different coating species (e.g., water, secondary organic, and brown carbon). The core and coating thickness varied between x to y and a to b, respectively. We found that clear and brown coatings enhance light absorption through the "lensing effect," with brown coatings showing a marked increase, both accounted for in the core-shell parameterization. This model-measurement approach improves predictions of TB optical properties.

Mie Theory

Atmospheric modeling


light absorption

light scattering

Optical properties

Core-shell particles 

Section on Statistics and the Environment