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Observed infrared spectral radiances from the Atmospheric Emitted Radiance Interferometer (AERI) during a severe desert dust storm in March 2006 over West Africa were compared to spectrally resolved, radiative transfer calculations. A good quality of fit was observed in the thermal infrared (7-14 mu m) bands however a significantly poorer fit was observed in the mid-near infrared (3-5 mu m) region. The sensitivity of the simulated radiance to the assumed particle shape and mono-modal size distribution was studied. Simulations using the scattering properties of prolate and oblate spheroids were compared to simulations from spheres. However, little sensitivity to shape was observed throughout the thermal and mid-near IR regions. Greater sensitivity to the size distribution shape was found; with residuals between observations and simulations in the 3-5 mu m region reduced when using a size distribution with a smaller width and a higher mode radius. However, the opposite was observed for the thermal IR region, suggesting a bi-modal distribution with different widths and mode radii would produce an Optimum fit in both bands simultaneously.