Analyses and Modeling of Relationships Between Ice Nuclei Concentrations, Aerosol Concentrations, and Ice Crystal Number Concentrations in Clouds

Anthony Prenni Colorado State University
Paul DeMott Colorado State University
Sonia Kreidenweis Colorado State University

Category: Aerosol Properties

Working Group: Cloud-Aerosol-Precipitation Interaction

Our project involves the re-examination of field experiment data characterizing aerosols, ice nuclei, and ice formation in clouds. The goals are, first, to determine if ice nuclei measurements predict ice formation in clouds, and second, to determine how ice nuclei number concentrations may be simply related to species and variables prognosed in numerical models (e.g., aerosol type and number concentration, temperature). Our approach uses combined data from multiple field studies in which measurements of the number concentrations of ice nuclei were made using a continuous flow diffusion chamber; aerosol number concentrations (as a function of size) were obtained around clouds; and ice crystal number concentrations and size distributions were obtained in clouds. Our analyses indicate that ice nuclei were responsible for the first ice formation in dynamically simple clouds where ice crystal number concentrations could be well defined, within instrumental limitations. Additionally, we confirmed that ice nuclei number concentrations above the boundary layer vary strongly with the number concentrations of larger-diameter particles (larger accumulation mode and coarse particles) and with temperature. We also present preliminary findings on the effects of aerosol composition, which indicate that ice nuclei concentrations are enhanced when the ambient aerosol is enriched in mineral dust and particle types associated with biomass burning. Finally, we present a simple first parameterization approach based on relating ice nuclei to aerosol number concentrations and temperature and describe its application in a host of models for studies of atmospheric implications.

This poster will be displayed at ASR Science Team Meeting.

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