CalWater 2 – Precipitation, Aerosols, and Pacific Atmospheric Rivers Experiment

Wednesday, 17 December 2014: 1:55 PM
J. Ryan Spackman1, F Martin Ralph2, Kimberly A Prather3, Daniel R Cayan3, Paul J DeMott4, Michael D Dettinger2, Chris W Fairall5, L. Ruby Leung6, Daniel Rosenfeld7, Steven A Rutledge4, Duane Edward Waliser8 and Allen B White5, (1)Science and Technology Corporation, Boulder, CO, United States, (2)Scripps Institute of Oceanography, La Jolla, CA, United States, (3)University of California San Diego, La Jolla, CA, United States, (4)Colorado State University, Fort Collins, CO, United States, (5)NOAA Boulder, Boulder, CO, United States, (6)PNNL / Climate Physics, Richland, WA, United States, (7)Hebrew University of Jerusalem, Jerusalem, Israel, (8)NASA Jet Propulsion Laboratory, Pasadena, CA, United States
Emerging research has identified two phenomena that play key roles in the variability of the water supply and the incidence of extreme precipitation events along the West Coast of the United States. These phenomena include the role of (1) atmospheric rivers (ARs) in delivering much of the precipitation associated with major storms along the U.S. West Coast, and (2) aerosols—from local sources as well as those transported from remote continents—and their modulating effects on western U.S. precipitation. A better understanding of these processes is needed to reduce uncertainties in weather predictions and climate projections of extreme precipitation and its effects, including the provision of beneficial water supply. This presentation summarizes the science objectives and strategies to address gaps associated with (1) the evolution and structure of ARs including cloud and precipitation processes and air-sea interaction, and (2) aerosol interaction with ARs and the impact on precipitation, including locally-generated aerosol effects on orographic precipitation along the U.S. West Coast. Observations are proposed for multiple winter seasons as part of a 5-year broad interagency vision referred to as CalWater 2 to address these science gaps (http://esrl.noaa.gov/psd/calwater). In January-February 2015, a field campaign has been planned consisting of a targeted set of aircraft and ship-based measurements and associated evaluation of data in near-shore regions of California and in the eastern Pacific. In close coordination with NOAA, DOE’s Atmospheric Radiation Measurement (ARM) program is also contributing air and shipborne facilities for ACAPEX (ARM Cloud Aerosol and Precipitation Experiment), a DOE-sponsored study complementing CalWater 2. Ground-based measurements from NOAA’s HydroMeteorological Testbed (HMT) network in California and aerosol chemical instrumentation at Bodega Bay, California have been designed to add important near surface-level context for the offshore measurements during AR landfall along the California coast.