Varied ice nucleating particle impacts on California winter storms

Description

Ice nucleating particles (INPs) impact the phase (ice/liquid), and precipitation development in all mixed-phase clouds. In this project, we compared the concentrations and compositions of INPs impacting the central California coast during the CalWater-2011 and ACAPEX (ARM Cloud Aerosol Precipitation Experiment) /CalWater-2015 campaigns, we are relating these measurements to cloud ice crystal observations using the DOE G-1 aircraft, and we are implementing INP parameterizations in models to explore how different INP populations present at different times are predicted to impact cloud and precipitation properties. The vital role of long range transported mineral dust particles on affecting winter storms in California was noted during CalWater-2011 studies (Creamean et al., Science, 2013; Fan et al., ACP, 2014). The role of varied concentrations of INPs of this type, and CCN, were further explored in Fan et al. (ACP, 2017). During the ACAPEX/CalWater-2015 (January to March 2015), INP measurements were obtained at a coastal site (UC Davis Bodega Marine Laboratory), on the G-1 aircraft, and alongside the DOE AMF-2 suite on the NOAA Ron Brown vessel offshore from CA. Single particle aerosol mass spectral data was also available on the G-1 and at the coastal site, and assorted other aerosol measurements were made. In contrast to 2011, mineral dust influences were not prevalent during the 2015 campaign, and air masses feeding cloud layers were sometimes dominated by sea spray aerosols. Consistent with this observation, the INP temperature spectra measured for immersion freezing often resembled those for marine aerosols produced from sea spray production (DeMott et al., PNAS, 2016). These INP types dominated during the major AR event that occurred during ACAPEX. Other results demonstrate that pollution aerosols do not specially contribute to INPs, and that a major rain event was followed by production of biological INPs that trended with certain categories of bioaerosols as detected by a real-time sensor and by sequencing of aerosol samples. Using developed parameterizations, modeling studies are underway to examine the consequences of different INP populations (mineral dust versus marine) on cloud system properties and precipitation. These include both idealized and case study WRF model simulations with spectral bin microphysics. Analyses of observed cloud microphysics in cases with different INP influences will also be presented.