Modeling of mineral dust in the atmosphere: Sources, transport, and optical thickness

TLDR

A global three‑dimensional model of the atmospheric mineral dust cycle is developed to study its impact on the radiative balance of the atmosphere. The model incorporates four dust size classes with source distributions tied to vegetation, soil texture, and moisture, parameterizes uplift and deposition using wind and rainfall statistics, simulates transport with the GISS tracer model, and derives monthly aerosol optical depths from the size‑dependent dust distribution. Simulated seasonal dust concentrations and size distributions largely agree with observations, though discrepancies highlight areas of significant land surface modification, and the model predicts a maximum seasonal mean aerosol optical depth of 0.4–0.5. The main uncertainties, about a factor of 3–5, in calculating optical thicknesses arise from the crude resolution of soil particle sizes, from insufficient constraint by the total dust loading in the atmosphere, and from our ignorance about adhesion, agglomeration, uplift, and size distributions of fine dust particles (<1 µm).

Abstract

A global three‐dimensional model of the atmospheric mineral dust cycle is developed for the study of its impact on the radiative balance of the atmosphere. The model includes four size classes of mineral dust, whose source distributions are based on the distributions of vegetation, soil texture and soil moisture. Uplift and deposition are parameterized using analyzed winds and rainfall statistics that resolve high‐frequency events. Dust transport in the atmosphere is simulated with the tracer transport model of the Goddard Institute for Space Studies. The simulated seasonal variations of dust concentrations show general reasonable agreement with the observed distributions, as do the size distributions at several observing sites. The discrepancies between the simulated and the observed dust concentrations point to regions of significant land surface modification. Monthly distribution of aerosol optical depths are calculated from the distribution of dust particle sizes. The maximum optical depth due to dust is 0.4–0.5 in the seasonal mean. The main uncertainties, about a factor of 3–5, in calculating optical thicknesses arise from the crude resolution of soil particle sizes, from insufficient constraint by the total dust loading in the atmosphere, and from our ignorance about adhesion, agglomeration, uplift, and size distributions of fine dust particles (&lt;1 μm).