Aerosol Atmospheric Rivers as Drivers of Extreme Poor Air Quality Events and Record PM2.5 Levels

This study investigates the impacts of aerosol atmospheric rivers (AARs) on extreme Particulate Matter 2.5 (PM2.5) levels (i.e. PM2.5 > 15μgm-3, daily guideline by the World Health Organization) and on aerosol optical depth (AOD) extremes (AOD > local 98th percentile) over the US and the globe, respectively, between 1997-2020. Results show that over various regions over the US, extreme PM2.5 values are associated with AARs up to 70% of the time. Dust (sulfate) AARs are primarily responsible for extreme PM2.5 levels over the southwestern (northeastern and the east coastal) US. Organic and black carbon AARs are associated with extreme PM2.5 levels over the Midwest region of the US. Globally, AARs are associated with 40-80% of the extreme AOD levels over the Sahel region, Europe, the Middle East, the US, South America, East Asia, India, and South Africa. Such associations often lead to the highest or the second-highest PM2.5 and AOD levels recorded during the study period over those stations.