Offshore transport episodes of anthropogenic sulfur in northern Chile: potential impact on the stratocumulus cloud deck

Subsiding easterly flow down the subtropical Andes often occurs in Northern Chile in connection with mid-latitude synoptic-scale disturbances, allowing for large anthropogenic emissions of oxidized sulfur from copper smelting to reach the stratus cloud deck. Here we analyze the synoptic-scale patterns associated with such transport events from reanalysis and local radiosonde data, and their seasonal and interannual variability within a 14-year period. A representative transport event is simulated using a 3-D transport chemistry model and the results are compared with satellite-derived cloud droplet radii. Altogether, this study suggests that there is a potential perturbation of the subtropical stratocumulus deck due to anthropogenic sulfur aerosols in terms of an observed decrease in cloud droplet radii despite the increase in liquid water content at some areas. Further research based on in situ measurements and characterization of active cloud condensation nuclei must be conducted.