Trace gas atmospheric rivers: remote drivers of air pollutants

Abstract. Understanding how, when, and where long-range transport of pollution impacts regional and local air quality is key to developing effective air quality management strategies. Here, we propose a new approach for the characterization of the long-range transport of trace gases. We extend and modify the "atmospheric river" concept used to describe rapid long-range transport of water vapor in order to identify and analyze the transport of tropospheric ozone (O₃) and two key ozone precursors, carbon monoxide (CO), and peroxyacetyl nitrate (PAN). We apply our trace gas atmospheric river (TGARs) detection algorithm to a 14-year Tropospheric Chemistry Reanalysis (TCR-2) dataset based on global chemical data assimilation products, spanning the period 2005–2019. Over this time period, we find more than 300,000 TGARs events globally. These events account for up to 60 % of total transport in some regions. We find that TGARs occur with a noticeably high frequency over mid-latitudes in both hemispheres (∼20 days per 3 months). These findings highlight the important role of rapid transport events in the long-range transport of pollution.