Abstract
Abstract. Dust emission is initiated when surface wind velocities exceed the threshold of wind erosion. Many dust models used constant threshold values globally. Here we use satellite products to characterize the frequency of dust events and land surface properties. By matching this frequency derived from Moderate Resolution Imaging Spectroradiometer (MODIS) Deep Blue aerosol products with surface winds, we are able to retrieve a climatological monthly global distribution of the wind erosion threshold (Vthreshold) over dry and sparsely vegetated surfaces. This monthly two-dimensional threshold velocity is then implemented into the Geophysical Fluid Dynamics Laboratory coupled land–atmosphere model (AM4.0/LM4.0). It is found that the climatology of dust optical depth (DOD) and total aerosol optical depth, surface PM10 dust concentrations, and the seasonal cycle of DOD are better captured over the “dust belt” (i.e., northern Africa and the Middle East) by simulations with the new wind erosion threshold than those using the default globally constant threshold. The most significant improvement is the frequency distribution of dust events, which is generally ignored in model evaluation. By using monthly rather than annual mean Vthreshold, all comparisons with observations are further improved. The monthly global threshold of wind erosion can be retrieved under different spatial resolutions to match the resolution of dust models and thus can help improve the simulations of dust climatology and seasonal cycles as well as dust forecasting.
Highlights
Mineral dust is one of the most abundant aerosols by mass and plays an important role in the climate system
The seasonal variations in the wind erosion threshold are largely due to the variations in dust optical depth (DOD) and surface wind frequency distributions that are in turn associated with variations in land surface features, such as soil moisture, soil temperature, snow cover, and vegetation coverage in each month
The climatological monthly Vthreshold was incorporated into the Geophysical Fluid Dynamics Laboratory (GFDL) AM4.0/LM4.0 model to examine the potential benefits relative to the use of a constant threshold
Summary
Mineral dust is one of the most abundant aerosols by mass and plays an important role in the climate system. Dust can serve as ice nuclei and affect the formation, lifetime, and characteristic of clouds (e.g., Levin et al, 1996; Rosenfield et al, 1997; Wurzler et al, 2000; Nakajima et al, 2001; Bangert et al, 2012), perturbing the hydrological cycle. Iron- and phosphorus-enriched dust is an important nutrient for the marine and terrestrial ecosystems and interacts with the ocean and land biogeochemical cycles (e.g., Fung et al, 2000; Jickells et al, 2005; Shao et al, 2011; Bristow et al, 2010; Yu et al, 2015)
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