Retrieving global distribution of threshold of wind erosion from satellite data

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 climatologically monthly global distribution of wind erosion threshold over dry and non-vegetated surface. This monthly two-dimensional threshold is then implemented in a Geophysical Fluid Dynamics Laboratory coupled land-atmosphere model (AM4/LM4). It is found that the climatology of dust optical depth (DOD) and total aerosol optical depth, surface PM2.5 and 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. Simulations with time-varying wind erosion thresholds also perform better than a constant annual-mean wind erosion threshold, as the latter overestimates DOD and surface dust concentrations in local dusty seasons. This 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.