Effect of particle characteristics on its optical properties

Atmospheric aerosols affect Earth's climate both directly and indirectly. The direct effect of aerosols on climate is by absorbing and/or scattering the incoming solar radiation and outgoing terrestrial radiation. This interaction strongly modifies Earth's radiation budget and hence the climate on regional and global scales. Much attention has been devoted to purely scattering aerosols, such as sulfate aerosols, mostly due to their "cooling effect". More recently, considerable attention has been directed to absorbing aerosols such as soot, dust, organics and mixed aerosols that contain absorbing species and inclusions. Absorbing aerosols can heat the atmosphere and affect atmospheric circulation and cloud formation (i.e., the semi-direct effect). There is a growing need to understand and measure atmospheric aerosol optical properties in order to better constrain their direct and semi-direct climatic effects.

We are using a newly built broadband cavity-enhanced spectrometers for studying the optical properties of aerosols and how these properties change with chemical reactions. Using this new experimental set up we can measure the complex index of refraction of the aerosols and calculate various parameters needed in climate models. Currently, our work focuses on the optical properties of secondary organic aerosols and biomass burning particles.

Molecular chemistry of atmospheric brown carbon

Molecular chemistry of atmospheric brown carbon. During a nationwide bonfire festival in Israel, Lag Ba’Omer, the chemical composition and optical properties of BrC chromophores were investigated using a high performance liquid chromatography (HPLC) platform coupled to photo diode array (PDA) and high resolution mass spectrometry (HRMS) detectors.