Linking the Different Diameter Types of Aspherical Desert Dust Indicates That Models Underestimate Coarse Dust Emission

Measurements of dust aerosol size usually obtain the optical or projected area-equivalent diameters, whereas model calculations of dust impacts use the geometric or aerodynamic diameters. Accurate conversions between the four diameter types are thus critical. However, most current conversions assume dust is spherical, even though numerous studies show that dust is highly aspherical. Here, we obtain conversions between different diameter types that account for dust asphericity. Our conversions indicate that optical particle counters have underestimated dust geometric diameter (D-geo) at coarse sizes. We further use the diameter conversions to obtain a consistent observational constraint on the size distribution of emitted dust. This observational constraint is coarser than parameterization used in global aerosol models, which underestimate the mass of emitted dust within 10 <= D-geo <= 20 mu m by a factor of similar to 2 and usually do not account for the substantial dust emissions with D-geo >= 20 mu m. Our findings suggest that models substantially underestimate coarse dust emission.

Automated summary

Accurate conversions between different diameter types of dust aerosols are critical, especially considering the aspherical shape of dust particles. Current optical particle counters underestimate dust geometric diameter at coarse sizes, leading to substantial underestimation of coarse dust emissions by global aerosol models. This highlights the need for improved measurements and models to better understand the emission and impact of dust aerosols.