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Linking the different diameter types of aspherical desert dust indicates that models underestimate coarse dust emission
  • Yue Huang,
  • Adeyemi Adebiyi,
  • Jasper Kok
Yue Huang
University of California Los Angeles

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Adeyemi Adebiyi
University of California Los Angeles
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Jasper Kok
University of California, Los Angeles
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Measurements of dust size usually obtain the optical or the projected area-equivalent diameters, whereas model calculations of dust impacts use the geometric and the aerodynamic diameters. As such, accurate conversions between the four types of diameters are critical. However, most current conversions assume dust is spherical, which is problematic as 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 using optical diameter to determine dust size underestimate dust geometric diameter at coarse sizes. We further use the diameter conversions to obtain a consistent observational constraint of size distributions of emitted dust in terms of geometric and aerodynamic diameters. The resulting size distributions are coarser than accounted for by parameterizations used in climate models, which which underestimate the mass of emitted dust within 10≤D_geo≤20 μm by a factor of ~2 and do not account for dust emission with D_geo≥20 μm. This finding suggests that current models substantially underestimate coarse dust emission.
28 Mar 2021Published in Geophysical Research Letters volume 48 issue 6. 10.1029/2020GL092054