Variable visibility?

2012-07-19 18:20:48.000 – Christopher Gregg,  Summit Intern

Mont Ham and Killington.

Over the past few weeks I have found myself enamored with the view around the summit of Mount Washington. I’ve had to opportunity to be able to familiarize myself with the surrounding peaks and how far away they are. Today was a day with great visibility. After getting my bearings, I noticed that Mont Ham, a whopping 106 miles away in Canada was faintly visible, while Killington, a mountain in Vermont about 88 miles away (18 miles closer) was not visible at all.

Obviously, visibility to the north was better than visibility to the West and South because of haze. Haze is an atmospheric phenomenon of obscured clarity in the sky that is caused by dust, smoke and other dry particles that are floating through the air. Where was this haze coming from though, and what was causing it?

Looking at weather maps over the last few days, there’s an area of low pressure hanging out over the Hudson Bay. Winds well above the surface of the earth typically follow isobars, or lines of equal pressure, and the isobars indicate that the majority of the air in the area is originating from North-Western Canada. Currently in that area, there are a number of forest fires emitting smoke into the atmosphere. So the smoke from wildfires in Canada is traveling South-East just South-West of the observatory giving it a more hazed appearance than to the North. Amazing how something happening so far away can be influential on our environment here!


Christopher Gregg,  Summit Intern

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