Linking the different diameter types of aspherical desert dust indicates an underestimation of coarse dust emission

Abstract:

Measurements usually determine dust size using either the optical or the projected area-equivalent diameters, whereas model calculations of dust impacts use the geometric or the aerodynamic diameters. As such, accurate conversions between the four types of diameters are critical. However, current conversions assume dust is spherical, which is problematic as measurements show that dust is highly aspherical. Here, we obtain conversions between different dust diameter types that account for dust asphericity. We find that after accounting for dust asphericity, optical particle counters, the most widely used sensors in in-situ measurements, underestimate dust size at coarse sizes. We further use the conversions between different dust diameter types to obtain a consistent data set of size distributions of emitted dust in terms of geometric and aerodynamic diameters. We find that the resulting emitted dust size distributions are substantially coarser than accounted for in current parameterizations. This finding suggests an underestimation of coarse dust emission by current models.