A study of the sensitivity of simulated mineral dust production to model resolution

The dependence of dust production on model grid-space resolution is investi gated using the Navy's operational mesoscale meteorological model with an i mbedded dust emission model. The study covers a 2-week period of strong dus t storms in April 1998 in the major dust source area of East Asia. The mode led surface winds at grid resolutions of 20, 40, 60, and 80 km are verified against observational data. At all resolutions the model has a positive bi as in wind speed that decreases as resolution increases. Dust fluxes that a re proportional to the fourth power of the friction velocity (u(*)) and the third power of the wind speed are calculated at all four resolutions and c ompared. Compared with the 20-km resolution u(*)-driven flux, which is dedu ced to be the most accurate, the u(*)-driven flux on the coarser grids over estimate the flux, with the 80 km being 60% higher for individual events an d nearly 20% higher in the total dust production for the entire study perio d. The wind-driven flux misses the smaller events due to the lack of a depe ndence on stability and wind shear, when compared with the timing of surfac e dust observations, and has differences of up to 70%, when compared with t he 20km u(*)-driven flux. Averaging over space and time tends to reduce the differences among grids and might support modeling at coarse resolution.