A34E-02:
Ice Nucleating Particles and their Role in California Winter Clouds

Wednesday, 17 December 2014: 4:15 PM
Paul J DeMott1, Kimberly A Prather2, Thomas Christopher James Hill1, Christina S McCluskey1, Ezra JT Levin1, Kaitlyn J Suski3, Jessie Creamean4, Douglas B Collins2, Andrew Martin5, Gavin Cornwell2, Hashim Al-Mashat2, Daniel Rosenfeld6, L. Ruby Leung7, Jennifer M Comstock8, Jason M Tomlinson8, Sonia M Kreidenweis9 and Markus D Petters10, (1)Colorado State University, Fort Collins, CO, United States, (2)University of California San Diego, La Jolla, CA, United States, (3)Colorado State University, Atmospheric Sciences, Fort Collins, CO, United States, (4)NOAA, Boulder, CO, United States, (5)University Corporation for Atmospheric Research, Boulder, CO, United States, (6)Hebrew University of Jerusalem, Jerusalem, Israel, (7)Pacific NW Nat'l Lab-Atmos Sci, Richland, WA, United States, (8)Pacific Northwest National Laboratory, Richland, WA, United States, (9)Colorado State Univ, Fort Collins, CO, United States, (10)North Carolina State Univ., Raleigh, NC, United States
Abstract:
Field studies are providing the opportunity to characterize ice nucleating particle (INP) number concentrations, their varied sources, and to examine their influence on ice formation and precipitation processes in winter clouds in California. Aerosol sources that may influence orographic cloud properties in California include pollution, marine aerosols, and transported dusts. Vertical stratification affects the role of different aerosol types. Boundary layer dust and pollution in Central Valley locations may influence cloud properties at times, but may be decoupled from cloud layers at other times or be restricted in affecting clouds by the Sierra barrier jet phenomenon. Marine layers may sometimes be lifted over topography to influence clouds. Finally, long range transported dust/biological particles may directly enter upper cloud levels to act as the trigger for ice initiation.

We present analyses of INP number concentrations, INP chemical composition, and related data collected from flights on the DOE G-1 aircraft during the CalWater 1 field study in winter 2011. Sampling of mostly marine boundary layer INP during the surface-based BBACPAX (Bodega Bay Aerosol-Cloud-Precipitation in Atmospheric rivers eXperiment) study in 2014 included first sampling with an online method for measuring the mass spectral composition of INP, and new immersion freezing INP measurements extending to the warm temperature limit of heterogeneous ice formation. Studies reveal the strong influence of long range transported aerosols on INP populations and typically lower INP concentrations in marine air layers. Plans for new studies including G-1 aircraft flights during the ACAPEX (ARM Cloud Aerosol Precipitation Experiment) study, overlapping with ground-based measurements in the CalWater-2 campaign in winter 2015 will be introduced.

Analyses are being applied toward numerical modeling studies of aerosol-cloud-precipitation interactions in California, presented separately in this session.

Back to: Precipitation—From Too Little to Too Much: Emerging Understanding of Atmospheric Rivers and Calwater Aerosol-Cloud Interaction Studies II
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