Studies of the distribution and speciation of ice nucleating particles feeding winter storms: Progress from CalWater and ACAPEX studies
Authors
Paul J. DeMott — Colorado State University
Ezra Ezra Levin Levin — Colorado State University
Thomas C Hill — Colorado State University
Kaitlyn Suski — Pacific Northwest National Laboratory
Christina S McCluskey — National Center for Atmospheric Research (NCAR)
Hashim Al-Mashat — UCSD
Gavin C. Cornwell — Pacific Northwest National Laboratory
Kimberly Prather — Scripps Institution of Oceanography
Hans P Taylor — North Carolina State University
Nicholas Rothfuss — NCSU
Markus D Petters — North Carolina State University
L. Ruby Leung — Pacific Northwest National Laboratory
Sonia Kreidenweis — Colorado State University
Left side: ACAPEX ice-nucleating-particle data normalized by aerosol surface area in comparison to data collected previously over marine regions, including during the MAGIC study (DeMott et al., 2016). Atmospheric river (AR) period data are highlighted in blue from ship and aircraft measurements. Right side: ATOFMS single-particle compositions measured in clear air on the ARM G-1 aircraft during ACAPEX (2015), with the AR period highlighted.
Ice nucleating particles (INPs) impact the phase (ice/liquid), lifetime, and precipitation development in all mixed-phase cloud regions. Previous studies suggest the vital role of long-range transported mineral dust particles in affecting winter storms in California, even in modulating precipitation during atmospheric river (AR) conditions (Creamean et al., 2013; Fan et al., 2014). U.S. DOE Atmospheric Radiation Measurement (ARM) Aerial Facility AAF-G1 data from that study (CalWater-2011) was supplemented by a more comprehensive suite of INP measurements during the CalWater-2015/ACAPEX (ARM Cloud Aerosol Precipitation Experiment) campaign (January to March, 2015), including measurements at a coastal site (UC Davis Bodega Marine Laboratory), on the G-1 aircraft, and alongside the DOE second ARM Mobil Facility suite on the NOAA Ron Brown vessel offshore from California. The alignment of similar measurement methods to cover the full range of mixed-phase cloud activation conditions, as well as single-particle aerosol mass spectral data, at two of these platform sites permitted assessment of the roles of different aerosol sources as INPs for winter storms in two seasons.
Here we summarize comprehensive analyses of spatial and temporal distributions of INPs active between 0 and -35 degrees C in the California region during ACAPEX and CalWater-2011. During ACAPEX and CalWater-2015, mineral dust influences appear to have been lower than during CalWater-2011, with a consequence that INP temperature spectrum via immersion freezing at many times resemble those found previously for marine aerosols produced from sea spray production. This is especially so through deep atmospheric layers during an AR event. These results are supported by the high proportion of marine aerosol compositions detected during the AR. Also during the AR events, INP concentrations were found to increase from open ocean toward land, even under primarily marine trajectories. Finally, production of possible biological INPs was evident throughout the boundary layer following the heavy AR rain period. We also show data on vertical distribution of INPs across the region that suggest spatial homogeneity at times, which will permit establishing distinct profiles of INPs for collaborative numerical modeling studies.
