Utilizing precipitation chemistry records to investigate the role of dust concentrations in `Atmospheric River' events from west US coastal states

Extreme precipitation events along the west coast of the US are commonly associated with atmospheric rivers (ARs), whereby extensive fluxes of moisture are transported outside the tropics and can result in major damage. Recent research has linked precipitation in the western US to airborne dust and other particles from the Sahara and Asian deserts. Increased amounts of dust can provide cloud condensation nuclei to form into cloud droplets and is expected to increase with a warming climate, thereby playing an important role in landfalling ARs. Currently, the CalWater 2015 campaign is measuring how aerosol particles interact with ARs, both offshore and when they reach the coast to determine how airborne dust affects the amount and type of precipitation that eventually falls. Results indicate a relationship between dust and biological aerosols detected in in situ cloud and precipitation residues. Understanding how dust concentration variations influence precipitation amounts can help to improve our knowledge of their influence on AR events. Many studies indicate that calcium (Ca2+) in polar ice cores is a good proxy of terrestrial dust. Additionally, a recent study in the southwestern US found rain and snow pH levels, usually between 5-6, exhibited their highest concentrations between March and June due mostly to dust, (crustal-derived species Ca2+, Mg2+, K+, and Na+) playing a major role in acid neutralization. Here we utilize United States Network for Isotopes in Precipitation (USNIP) and National Atmospheric Deposition Program (NADP) weekly precipitation amount and chemistry records from 1981 to 2015 to investigate the average ion concentration variations of Ca, Mg, K, Na, and the pH to determine if and how they changed during AR events. We analyze a North-South transect of sites across the US coastal states (WA, OR, and CA) which received extreme precipitation (>100 mm) and coincide with noted AR events. We also utilize PERSIANN-CONNECT, a global extreme precipitation event database, to investigate climate variables.