This isn't a question, but it's something I found while doing research for something else. It might be helpful for others. https://mae.ucf.edu/fcrar2018/wp-content/uploads/2018/05/8_FPU-Visibility-Drake-Luckey-Erickson-cr.pdf Ever struggle to come up with an idea of how dense a "Dense Fog" really is? How about a moderate fog, or just a thin fog or a haze? How about how far you might expect to see on an "Very Clear" day? Well, now you know! There's apparently a scientific difference between "Fog" and "Mist." Interestingly, by this definition, Steven King's Mist was not.
Code 0, Dense Fog= <50m Code 1, Thick Fog= 50-200m Code 2, Moderate Fog= 200-500m Code 3, Light Fog= 500-1000m Code 4, Thin Fog= 1000-2000m Code 5, Haze= 2000-4000m Code 6, Light Haze= 4000-10000m (that's about 2.5 to 6 miles, that's probably a clear day by the standards of some places) Code 7 Clear= 10000-20000m Code 8 Very Clear= 20000-50000m Code 9 Exceptionally Clear >50000m It's possible to see up to 120 miles on a clear enough day and with good enough optics. That would be "see the skyscrapers of Atlanta from a mountain in Tennessee" clear.
When I was a lad we spent every summer vacation with my grandparents in Maine. Most days, from my grandparents' porch we could see an island that's 17 miles offshore. On some days, though, we couldn't see the bell buoy at the entrance to the harbor -- that was less than 500 meters from the house.
East Tennessee is like that. You can spend a night stargazing on the shore of Nickajack or Watts Bar Lake, and the next day you wake up to fogbanks as thick as pea soup. Real fun trying to get around the mountains in those conditions.
Some Highways in Europe have fog markings on their sides. White markings at regular intervals to help determine how low visibility is; driver's advice depends on how many markers you can see ahead of you at a time. These markings soaked into everyday speech and when we're referring to how dense the fog is, we sometimes go based on these markers. EG, a "dense fog" will be mutually understood as a situation where only one marker is visible, whereas a "light fog" will be where most markers are visible.
