Dust emission is initiated when surface wind velocities are greater than the threshold of wind erosion. Most dust models used constant threshold values globally. Here we use satellite products to constrain the frequency of dust events and surface characteristics. 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 wind erosion threshold (Vthreshold) over dry and non-vegetated surface. This monthly two-dimensional threshold velocity is then implemented in 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 seasonal cycle of DOD are better captured over the “dust belt” (i.e. North Africa and the Middle East) by simulations with the new wind erosion threshold than those with the default globally constant threshold. The most significant improvement is achieved with the frequency of dust events, which is generally ignored in model evaluation. By using monthly rather than annual mean Vthreshold, all comparisons with observation are further improved. This monthly global threshold of wind erosion can be retrieved under different resolutions to match the resolution of dust models and may improve the climatology and seasonal cycle of dust simulation as well as dust forecasting.
GFDL Lunchtime Seminar
Wed, Dec 19, 2018, 12:00 pm to 1:00 pm
Smagorinsky Seminar Room 209