What Makes an Atmospheric River Dusty?

Trans-Pacific dust has previously been identified from aircraft measurements and precipitation residues collected during land-falling Atmospheric Rivers in Northern California and is thought to impact cloud phase and precipitation amounts by acting as ice nucleating particles. This study uses a new observational dataset of dust aerosol optical depth (DAOD) and meteorological information from Modern-Era Retrospective analysis for Research and Applications, Version 2 (MERRA-2) to take a deeper look into synoptic conditions that lead to the entrainment of trans-Pacific dust aerosol within atmospheric rivers as well as the seasonality and frequency of these dusty events. In this work, we introduce a system for categorizing land-falling atmospheric river events with a “dust score” based on DAOD. We find that dusty atmospheric rivers are associated with cyclogenesis over northwestern China and Mongolia, and with an extended mode of the Pacific jet stream. The frequency of dusty atmospheric rivers has an annual maximum in March, when the end of the peak AR season (Oct-Mar) overlaps with the beginning of the dust storm season in Asia (Mar-May). Identification of dusty atmospheric rivers and the associated synoptic conditions under which they occur will allow for further investigation of the relationship between dust aerosol and precipitation outcomes associated with atmospheric rivers.