Why do salt particles and heating provide only limited relief from fog above freezing?

Techniques such as seeding with salt particles or using heat to clear fog at temperatures above freezing provide only short-term relief under limited conditions because they do not address the underlying atmospheric processes that sustain the fog.1

While heating—such as the historical FIDO (Fog Investigation Dispersal Operations) method—works by decreasing the relative humidity of the air to induce droplet evaporation, it requires large quantities of energy to maintain visibility improvements. Similarly, seeding with salt particles, such as calcium chloride, was attempted in the past but proved impractical for sustained or widespread use.2

In contrast, fog dispersal is more effectively achieved in sub-freezing conditions by seeding with carbon dioxide or propane, which utilizes the properties of supercooled water droplets to convert them into ice crystals. Because fog formation is a complex process involving condensation and often multiple simultaneous physical factors, simple interventions at temperatures above freezing struggle to overcome the environmental conditions that maintain the fog layer.123