Impact of dust aerosols on precipitation associated with atmospheric rivers using WRF-Chem simulations

The trans-Pacific transport of dust aerosols to the western United States coincided with the landfall of an atmospheric river (AR) from 17 to 18 February 2011 during the California Water Service (CalWater) field campaign in northern California. Weather Research and Forecasting model with Chemistry (WRF-Chem) simulations are conducted to quantitatively understand the impact of long-range transported (LRT) dust aerosols on precipitation processes associated with AR events impacting the western United States. The simulations show that CCN activation of dust aerosols can limit cloud water autoconversion upwind of the Sierra Nevada, which influences additional cloud water over the windward slopes and, therefore, more efficient snow accretion and larger precipitation totals in the higher terrain. Latent heating associated with snow accretion can promote enhanced vertical motions, which can lead to additional snow production and precipitation across the Sierra Nevada.