P73 Using WRF-Chem to simulate the aerosol-cloud-precipitation processes associated with landfalling rivers.

Naeger, Aaron, University of Alabama in Huntsville

The presence of dust aerosols among landfalling atmospheric rivers (ARs) along the West coast of the United States is not uncommon, especially during the late winter, when the strong surface winds of East Asian winter monsoon efficiently pick up and loft desert dust into the atmosphere, which allows the strong mid- to upper-level winds to carry the particles across the Pacific Ocean.  Intensive measurements during the CalWater field campaign in northern California from Feb-March 2011 found dust particles acting as cloud condensation nuclei (CCN) and ice nuclei (IN) within landfalling ARs.  We conduct WRF-Chem simulations using a double-nested configuration with 4- and 1.33 km horizontal grid spacing centered over the CalWater field campaign to simulate the aerosol-cloud-precipitation processes associated with a dusty AR event from 17-19 February 2011.  Model results indicate that the efficient CNN activation of dust leads to an increase in cloud water, and consequently, an increase in snow and precipitation in the higher terrain of the Sierra Nevada.  Ongoing work involves comparing model results to the intensive field observations, and performing additional sensitivity simulations to understand the impact of other aerosol species on landfalling ARs.