Collaborative Research: Impacts of Mineral Dust on the Lifecycle of Tropical Convection

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The effects of mineral dust acting as both cloud condensation and ice nuclei within organized convective cloud systems over the tropical Atlantic basin will be investigated through a combination of observational analysis and numerical simulations. Idealized simulations will be conducted using the Regional Atmospheric Modeling System (RAMS) to further examine dust aerosol impacts on tropical convective clouds and precipitation are to be guided by observations collected during NAMMA, NASA's African Monsoon Multidisciplinary Activities project, conducted during the 2006 Atlantic hurricane season. The lifecycle of an actual storm (Tropical Storm Debby), which was apparently influenced by ingestion of Saharan dust over the eastern Atlantic, will be simulated in detail. The dynamical and radiative impacts of the Saharan Air Layer (SAL, which carries dust westward from Africa) will be studied, and the relative importance of direct and indirect aerosol effects as well as environmental influences of the SAL itself--including humidity, temperature and vertical wind shear--will be assessed. Observations of aged dust reaching the far western Atlantic upon deep convective clouds in that region will be examined using additional observations from the NSF-supported PREDICT (Pre-Depression Investigation of Cloud-systems in the Tropics) experiment in 2010.The intellectual merit of this effort centers on improved understanding of cloud processes (and in particular cloud and precipitation microphysics) in the presence of influences by dust and other aerosols originating over distant continental regions, and determination of the extent to which these influences may favor or disfavor tropical storm and hurricane formation.Broader impacts will come through support of two principal investigators drawn from an underrepresented group (viz. women in the atmospheric sciences), through a combination of university training and field experience for a graduate student, and ultimately through improved ability to anticipate dust-induced changes in tropical storm formation and/or intensity key to accurate forecasts of Atlantic basin hurricanes.