Climate Models and Remote Sensing Retrievals Neglect Substantial Desert Dust Asphericity

Climate models and remote sensing retrievals generally assume that dust aerosols are spherical or spheroidal. However, measurements show that dust aerosols deviate substantially from spherical and spheroidal shapes, as ratios of particle length to width (the aspect ratio) and height to width (height...

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Bibliographic Details
Published in:Geophysical research letters 2020-03, Vol.47 (6), p.n/a
Main Authors: Huang, Yue, Kok, Jasper F., Kandler, Konrad, Lindqvist, Hannakaisa, Nousiainen, Timo, Sakai, Tetsu, Adebiyi, Adeyemi, Jokinen, Olli
Format: Article
Language:English
Subjects:
Aerosols
Arid climates
Aspect ratio
Asphericity
Atmospheric particulates
Climate
Climate models
Deserts
Detection
Dust
Dust storms
Dust transport
Gravity
Height
Length
Ratios
Remote sensing
Transport
Width
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Summary:Climate models and remote sensing retrievals generally assume that dust aerosols are spherical or spheroidal. However, measurements show that dust aerosols deviate substantially from spherical and spheroidal shapes, as ratios of particle length to width (the aspect ratio) and height to width (height‐to‐width ratio) deviate substantially from unity. Here, we quantify dust asphericity by compiling dozens of measurements of aspect ratio and height‐to‐width ratio across the globe. We find that the length is on average 5 times larger than the height and that climate models and remote sensing retrievals underestimate this asphericity by a factor of ~3–5. Compiled measurements further suggest that North African dust becomes more aspherical during transport, whereas Asian dust might become less aspherical. We obtain globally‐averaged shape distributions, from which we find that accounting for dust asphericity increases gravitational settling lifetime by ~20%. This increased lifetime helps explain the underestimation of coarse dust transport by models. Key Points A compilation of measurements shows that current climate models and remote sensing retrievals substantially underestimate dust asphericity Measurements suggest that North African dust becomes more aspherical during transport, whereas Asian dust might become less aspherical Dust asphericity increases gravitational settling lifetime by ~20%, which helps explain the underestimation of coarse dust transport by models
ISSN:0094-8276
1944-8007
DOI:10.1029/2019GL086592