Aerosol characteristics in the entrainment interface layer in relation to the marine boundary layer and free troposphere
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Authors
Dadashazar, Hossein
Braun, Rachel A.
Crosbie, Ewan
Chuang, Patrick Y.
Woods, Roy K.
Jonsson, Haflidi H.
Sorooshian, Armin
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2018-02
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Abstract
This study uses airborne data from two field campaigns off the California coast to characterize aerosol size distribution characteristics in the entrainment interface layer (EIL), a thin and turbulent layer above marine stratocumulus cloud tops, which separates the stratocumulus-topped boundary layer (STBL) from the free troposphere (FT). The vertical bounds of the EIL are defined in this work based on considerations of buoyancy and turbulence using thermodynamic and dynamic data. Aerosol number concentrations are examined from three different probes with varying particle diameter (Dp) ranges: >?3?nm, >?10?nm, and 0.11–3.4?µm. Relative to the EIL and FT layers, the sub-cloud (SUB) layer exhibited lower aerosol number concentrations and higher surface area concentrations. High particle number concentrations between 3 and 10?nm in the EIL are indicative of enhanced nucleation, assisted by high actinic fluxes, cool and moist air, and much lower surface area concentrations than the STBL. Slopes of number concentration versus altitude in the EIL were correlated with the particle number concentration difference between the SUB and lower FT layers. The EIL aerosol size distribution was influenced by varying degrees from STBL aerosol versus subsiding FT aerosol depending on the case examined. These results emphasize the important role of the EIL in influencing nucleation and aerosol–cloud–climate interactions.
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The article of record as published may be found at http://dx.doi.org/10.5194/acp-18-1495-2018
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Office of Naval Research [N00014-10-1-0811, N00014-11-1-0783, N00014-10-1-0200, N00014-04-1-0118, N00014-16-1-2567]
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This publication is a work of the U.S. Government as defined in Title 17, United States Code, Section 101. Copyright protection is not available for this work in the United States.