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Edited on Tue Aug-23-05 01:02 PM by Ready4Change
Clouds reach from ground level (fog) to 10's of thousands of feet in the air. Thunderheads can go higher than airliners fly, commonly over 45,000 ft, reportedly reaching as high as 75,000. Those high, wispy cirrus clouds are actually suspended ice crystals, and can be from 18,000 on up.
So, say you're looking at the top of a distant thunderhead that's just visible over the horizon. If its 45,000 feet up, thats about 15,000 meters (15km.) That's about 460km away, according to the chart. Also, add to that your own distance from the horizon, which is about 5km due to your being almost 2m tall. So you get 465km.
465km = 289 miles. About 289 miles to that cloud head JUST poking above the horizon.
Now, can you REALLY see that far? Probably not. Surface haze in the lower atmosphere usually "fogs out" anything you might see that low on the horizon. That's why, in many pictures, the top of a mountain may look crystal clear, but the bottom is almost invisible in haze. The lower amosphere is full of moisture and particulates that turn it into a kind of fog.
Plus, unless you are at sea, the actually horizon is probably blocked by land features. On land you often cannot actually see the horizon. You just see the top of the nearest ridgeline.
The end result is that, on a nice clear day, on relatively flat land, you might be seeing clouds 100-125 miles away. More likely they are only 25-50 miles away or so.
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