Asian Long-range Transport in Relation to Atmospheric Rivers in Northern California

Abstract

The study investigated the effect of aerosol long-range transport on precipitation over northern California during atmospheric river (AR) events in the 2017 cold season (January-April). ARs in 2017 were among the strongest to date and the intense precipitation associated with the ARs resulted in flooding, destruction of property, and contamination of water supplies. The aerosol optical depth (AOD) from Moderate Resolution Imaging Spectroradiometer (MODIS) data showed Asian dust traveling across the northern Pacific Ocean along with AR events. Aerosol measurements in California, provided by the Interagency Monitoring of Protected Visual Environments (IMPROVE), showed that more Asian dust tends to be observed over the coast while non-Asian/localized dust is observed inland. A mixture of Asian and localized dust was observed over the mountains, although higher amounts of both were observed in the spring (March-April). Back trajectory analysis confirmed that Asian aerosols were transported along with the air parcels, and each AR event had its own transport pattern in terms of horizontal advection and vertical lifting. The study resulted in low correlations between precipitation and aerosols, which suggests that aerosols contributed little to the increase of local precipitation during the 2017 AR events.