Environmental Science and Engineering Seminar

Mineral dust particles are critical to the Earth's climate system because they account for approximately ~25 % of the shortwave radiation scattered and absorbed by all aerosols in the atmosphere. But despite the importance of these radiative effects, the amount of shortwave radiation absorbed by atmospheric dust remains largely unclear. This is because knowledge of dust absorption properties, characterized by the dust aerosol absorption optical depth, primarily depends on the dust size distribution and the complex refractive index, which are difficult to observe from remote-sensing platforms. As a result, climate model simulations and retrieval algorithms rely on certain assumptions about dust properties that have led to significant uncertainties in their estimation of the global dust absorption optical depth. In this talk, I will describe a framework that leverages dozens of in-situ measurements of the dust size distribution and single-scattering albedo to obtain a more accurate constraint on the global dust absorption optical depth at 550-nm wavelength. I will show that atmospheric dust is much coarser with significant spatial variability in the imaginary refractive index than represented in climate models. Consequently, I will show that amount of solar radiation absorbs by dust differs substantially from what climate models simulate, which has important implications for the Earth's energy balance.