PNNL

Abstract

Mineral dust contributes up to one-half of surface aerosol loading in spring over the southwestern U.S., posing an environmental challenge that threatens human health and the ecosystem. Here, we identify four typical dust transport patterns across the Sierra Nevada, associated with the mesoscale winds, Sierra-Block-Jets (SBJ), North-Pacific-High (NPH), and long-range cross-Pacific westerlies, respectively. We find dust emitted from the Central Valley is persistently transported eastward, while dust from the Mojave Desert and Great Basin influences the Sierra Nevada during mesoscale transport mostly occurring in winter and early spring. Asia dust reaching the mountain range comes either from the west through straight isobars (cross-Pacific transport) or from the north in the presence of NPH. Extensive depositions on mountain snow surface are found on the west slope, contributed by Central Valley emissions and cross-Pacific remote transport. Especially, the SBJ-related transport produces deposition through landfalling atmospheric rivers, whose frequency might increase in a warming climate.