Abstract
Vegetation is a major control on dust emission because it extracts
momentum from the wind and shelters the soil surface, protecting dry and
loose material from erosion by winds. Many traditional dust emission
models (TEMs) assume that the Earth’s land surface is devoid of
vegetation, adjust dust emission using a vegetation cover complement,
and calibrate the magnitude of modelled emissions to atmospheric dust.
We compare this approach with a novel albedo-based dust emission model
(AEM) which calibrates Earth’s land surface normalised shadow (1-albedo)
to shelter depending on wind speed, to represent aerodynamic roughness
spatio-temporal variation. Existing datasets of satellite observed dust
emission from point sources (DPS) and dust optical depth (DOD) show
little spatial relation and DOD frequency exceeds DPS frequency by up to
two orders of magnitude. Relative to DPS frequency, both dust emission
models showed strong relations, but over-estimate dust emission
frequency, suitable for calibration to observed dust emission. Our
results show that TEMs over-estimate large dust emission over vast
vegetated areas and produce considerable false change in dust emission,
relative to the AEM. It is difficult to avoid the conclusion, raised by
other literature, that calibrating dust cycle models to atmospheric dust
has hidden for more than two decades, these TEM modelling weaknesses and
its poor performance. The AEM overcomes these weaknesses and improves
performance without masks or vegetation cover. Considerable potential
exists for Earth System Models driven by prognostic albedo, to reveal
new insights of aerosol effects on, and responses to, contemporary and
environmental change projections.