Saharan dust transport to the Caribbean during PRIDE: 1. Influence of dust sources and removal mechanisms on the timing and magnitude of downwind aerosol optical depth events from simulations of in situ and remote sensing observations

[1] Dust emissions, transport, and deposition are simulated for the Puerto Rico Dust Experiment (June-July, 2000) with a three-dimensional aerosol transport model driven by assimilated meteorology. Sensitivity to the dust source formulation is tested by comparing simulations run with two different source modules to TOMS and AERONET measurements. Central and east African dust sources are more accurately simulated with the Ginoux et al. [2001] source model than with the Marticorena and Bergametti [1995] source model. The timing of high aerosol optical depth (AOD) dust events at Puerto Rico is largely independent of the timing of dust emissions, implying a persistent reservoir of suspended dust particles exists over Africa and that the timing of downwind dust events is more strongly coupled to transport dynamics than to the dust source model chosen. The downwind AOD and particle size distribution are accurately simulated using the dust particle size distribution produced by the Ginoux et al. [2001] source model or by fitting the Marticorena and Bergametti [1995] dust emissions to the d'Almeida [1987] background desert aerosol particle size distribution. The dust distribution determined by fitting the Marticorena and Bergametti [1995] emissions to the Schulz et al. [1998] initial particle size distribution produces aerosol optical depths that are consistently too high. Large dust particles observed far downwind of source areas may be partially explained if they are treated as flat disks rather than spheres in the particle fall velocity calculation. With the Ginoux et al. [2001] source model we estimate African and Arabian dust emissions during July 2000 to be 214 Tg for particles smaller than 10 mm radius. Nineteen percent of the emitted mass is transported west of Africa and over the North Atlantic. Twenty percent of the dust leaving Africa passes west of Puerto Rico.