Direct and indirect impacts of Saharan dust acting as cloud condensation nuclei on tropical cyclone eyewall development

The mechanisms by which Saharan dust acting as cloud condensation nuclei (CCN) impact tropical cyclone (TC) evolution were examined by conducting numerical simulations of a mature TC with CCN added from lateral boundaries. CCN can affect eyewall development directly through release of latent heat when activated and subsequent growth of cloud droplets and indirectly through modulating rainband development. Convection in the rainbands was negatively correlated with that in the eyewall in all simulations. The development of rainbands tended to promote latent heat release away from the eyewall, block the surface inflow and enhance cold pools. The maximum impact of rainbands on the eyewall (or vice versa) occurred with a time lag of 3.5 to 5.5 hr. The convection in the eyewall and rainbands did not show a monotonie relationship to input CCN due to the non-linear feedback of heating from a myriad of microphysical processes on storm dynamics.