Not true; moisture does not need to be visible. No fog, no mist, etc. When an airfoil moves through air, it creates low pressure zones where moisture can condense and freeze onto the airfoil surfaces.
I’m not familiar with what you are describing. Is that a theoretical principle or are airframes icing and planes crashing from clear air icing?
. From the Aeronautical Information Manual (AIM) sect. 7-1-19:
“b. A pilot can expect icing when flying in visible
precipitation, such as rain or cloud droplets, and the
temperature is between +02 and −10 degrees Celsius.
When icing is detected, a pilot should do one of two……”
And directly from the FAA Website on structural icing:
“Two conditions are necessary for structural icing in flight: (1) the aircraft must be flying through visible water such as rain or cloud droplets, and
(2) the temperature at the point where the mois- ture strikes the aircraft must be 0° C or colder. Aerodynamic cooling can lower temperature of an airfoil to 0° C even though the ambient tempera- ture is a few degrees warmer.”
In the last 25 years of Instrument flying I’ve seen all types of ice. I’ve never accreted ice in clear air. I’d be interested in any literature you know of to learn more about what you’re describing.