AAAR 35th Annual Conference October 17 - October 21, 2016 Oregon Convention Center Portland, Oregon, USA
Abstract View
Changes in Precipitating Snow Chemistry with Location and Elevation in the California Sierra Nevada
JESSICA AXSON, Jessie Creamean, Amy Bondy, Rebecca Craig, Nathaniel May, Hongru Shen, Michael Weber, Kerri Pratt, Andrew Ault, University of Michigan, Ann Arbor MI
Abstract Number: 464 Working Group: Aerosols, Clouds, and Climate
Abstract Orographic snowfall in the California Sierra Nevada Mountains is an important source of water for California and can vary significantly on an annual basis. The microphysical properties of orographic clouds and precipitation formation are impacted by aerosols of varying size, number, and chemistry, which are incorporated into clouds formed along the Sierra barrier. The physicochemical properties and sources of insoluble residues and soluble ions found in precipitation samples were explored for three sites of variable elevation in the Sierra Nevada during the 2012 ‒ 2013 winter season. Residues were characterized using nanoparticle tracking analysis (NTA), Raman microspectroscopy, scanning electron microscopy (SEM-EDX), and ion chromatography (IC) to determine the size-resolved number concentrations and associated chemical composition. A transition in the aerosol sources that served as cloud seeds or were scavenged in- and below-cloud was observed as a function of location and elevation. The transition with increasing elevation to aerosols that serve as ice nucleating particles may impact the properties and extent of snowfall in remote mountain regions where snowpack provides a vital supply of water. The residues and soluble ions observed provide insight into how multiple aerosol sources can impact cloud and precipitation formation processes, even over relatively small spatial scales.