Competition between Sea Salt and Sulfate Particles as Cloud Condensation Nuclei

The influence of sea salt on the cloud droplet activation of sulfate particles is investigated using a size-resolving model of the aerosol activation process. The authors found that the total number concentration of activated cloud droplets increases with increasing sea salt concentration if the sulfate number concentrations are relatively low and updrafts are strong, but it decreases with higher sea salt if sulfate number concentrations are high and cloud updrafts are weak. The increase is due to the activation of accumulation mode sea salt particles, while the decrease is due to the reduction in maximum cloud supersaturation due to competition with coarse mode sea salt particles. These conclusions are insensitive to the sulfate size distribution and surface wind speed.