Using MODIS AOD Assimilation to Assess the Impact of Mineral Dust on the Genesis and Evolution of Hurricane Ernesto (2006)

Mineral dust can impact the atmosphere in two primary ways: (1) by directly absorbing, scattering, and emitting short and longwave radiation (radiative effects), and (2) acting as cloud condensation or ice nuclei, indirectly affecting cloud optical and physical properties as well as precipitation processes (microphysical effects). During boreal summer, mineral dust plumes from North Africa are advected well into the tropical North Atlantic and can regularly be found in close proximity to tropical cyclones (TCs) or their seed disturbances, particularly in the Atlantic Main Development Region, potentially affecting their development and evolution. Many studies indicate that dust radiative effects within African dust plumes alter vertical and horizontal temperature gradients in such a way that may increase mid-level wind shear and static stability in the tropical Atlantic, altering TC development and/or track. The effects of dust microphysics on TCs, on the other hand, are less certain but an increasing body of research suggests that they depend on TC strength, environmental conditions, and how close dust aerosols are to the storm center. Hurricane Ernesto (2006), whose precursor African Easterly Wave disturbance traveled across the Atlantic in close association with a large, persistent dust plume, is one such storm whose development may have been greatly influenced by dust physical processes. The storm developed only after the eventual dissipation of the plume in the eastern Caribbean. In this study, we examine the impact of mineral dust on the genesis and evolution of Hurricane Ernesto with a series of numerical experiments using a modified, dust-capable version of the WRF model and analyses created by assimilating meteorological and MODIS AOD observations within the GSI 3DVAR software framework. The impacts of MODIS AOD assimilation on the simulated dust distribution and forecasts of Ernesto’s development are highlighted.