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

摘要

An outstanding meteorological feature appearing off the coast in Central and Northern Chile is the persistent stratus cloud deck under the subtropical Pacific High. It has a large impact on the regional and global energy balance and atmospheric circulation. In connection with mid-latitude synoptic-scale disturbances, subsiding easterly flow down the subtropical Andes often occurs in Northern Chile allowing large anthropogenic emissions of oxidized sulfur that take place in the region to reach the stratus deck. We explore the potential impact of anthropogenic emitted sulfur on the stratus deck associated with strong easterly flow events that occur on the average 4 to 8 times per year. A representative transport event is simulated using a 3-D transport chemistry model and the results are compared with satellite observations of cloud droplet number concentration. Although not conclusive, this preliminary study reveals a potential perturbation of the subtropical stratocumulus deck due to anthropogenic sulfur aerosols.