Combined Lab, Field, and Modeling Studies Aimed to Improve our Understanding of Sources of Ice Nuclei and their Impact on Western US Precipitation Processes

University Of California-San Diego, La Jolla CA

Investigators

Abstract

This project builds upon the CalWater study conducted in 2009-2011 in California that investigated the impact of dust and bioparticles transported over long distances on clouds and precipitation processes over the Sierra Nevada mountain range. It is part of a larger project sponsored by the Department of Energy and the National Oceanic and Atmospheric Administration. This research seeks to gain a better understanding of the interactions between aerosols and clouds in the atmosphere and how these interactions influence precipitation processes. The results may be important for areas of California suffering from recent drought. The project will address 3 questions: (1) Under which regimes do the ice nucleating properties of mineral dust, terrestrial, and marine biology origin impact mixed-phase, precipitating cloud systems? (2) How do the ice nuclei (IN) activity spectra differ between dust, bio-dust and bio-marine aerosols, and can these differences be adequately represented in numerical weather prediction models? And (3) Do scenarios of optimal IN number concentration, together with cloud microphysics and dynamic responses exist such that precipitation is enhanced? Individual particle and IN mass spectra will be measured at a ground site using aerosol time-of-flight mass spectrometry (ATOFMS) and combined with data from other instruments on the ground and on the DOE aircraft, including a continuous flow diffusion chamber (CFDC), to provide information on the mixing state and sources of the aerosols. The Weather Research and Forecast model with aerosol speciated spectral bin microphysics (WRF-ASBM) will be run at cloud-resolving resolution and constrained by measured aerosol chemical type, IN concentrations, cloud water content and hydrometeor type measured by in-cloud imagery. The observations will be used to constrain and validate advanced numerical model simulations of aerosol cloud nucleation, hydrometeor-hydrometeor interaction, and precipitation. The results will have major implications for the field of aerosol-cloud interaction studies.