Date/Time: February 25, 2015 (Wednesday) noon

Where: Center for Atmospheric Sciences Class Room (Phenix 123)

Speaker: Chelsea Coor

From: NASA Langley

Topic: Observational Evidence for the Convective Transport of Dust over the Central United States

Abstract: Mineral dust, one of the most abundant primary aerosols in the atmosphere, indirectly impacts climate by modifying ice (cirrus) cloud radiative properties during the formation of these clouds. In order for dust to participate in cirrus formation, it must be present in the upper troposphere. Modeling studies, together with observations, indicate deep convection is generally a good transport mechanism for both gases and aerosols, including dust, from the boundary layer to the upper troposphere. However, inconsistencies between modeled and observed convective dust transport efficiencies indicate the transport mechanism of dust through convective systems is not well established. In this talk, the transport efficiency of coarse mode dust through nine storms encountered over Colorado (CO) and Oklahoma (OK) is examined. Bulk aerosol composition and aerosol volume size distribution data used for the analysis were collected aboard the NASA DC-8 aircraft during the Deep Convective Clouds and Chemistry Experiment mission in May/June 2012. Comparisons between measurements made at low altitudes in the storm inflow region and those made in the outflow (storm anvil) indicated over 50% of the ingested coarse mode dust was transported through these CO and OK storms. Additionally, mean inflow aerosol number concentrations calculated over an ice-nuclei-relevant diameter range were substantially higher than ice particle concentrations for all storms. Therefore, a significant fraction of the transported dust was not activated as ice nuclei during anvil formation.

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