Atmospheric occurrences that decrease visibility, particularly fog, smoke, smog and the like, are cleared at sites such as airports by an array of EGD spray units emitting submicron size charged water droplets to attach to airborne particulates and electrostatically precipitate those to ground. Independent variables of the array and the EGD jets from the spray units are controlled to control the dependent variables characterizing the space-charge cloud thus developed. The methods and apparatus control the height to which clearing of the airborne particulates occurs to improve visibility and the time required for such clearing. Specific compact spray units are self-contained, can be radio operated, and are movable. Placement of the units for removal of radiation and advection fog with respect to airport runways include a square array of the spray units proximate the runway for radiation fog control and upwind location of arrays for advection fog precipitation. Specific characteristics of small, medium and large spray units suitable for use in the arrays are set forth.