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I take landscapes. This fall and early winter I've been noticing haze is fairly common. It doesn't take much to ruin distant subjects, like mountain peaks, here in my home state of Colorado. Most notably I lugged my large format camera out to the alps in October only to find a nearly constant haze for my entire two weeks. I asked around and locals said it was common in the fall.

Is there some way to predict haze for any given day? Or to know when a broader area like the alps might be more prone to it?

  • It seems like it would be related to the Dew Point. (But I'm not a meteorologist, so not positive.) – user1118321 Dec 26 '17 at 3:08
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  • Thanks @doug. I suspect even a max visibility of 99, ideal for aviation, could have enough haze to ruin an intended high-detail photograph. Good to have more background on the concept though 👍 – steel Dec 26 '17 at 15:04
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Predict? I doubt it.

Factors that contribute to haze:

  • Warm daytime temps that allow plants to emit various hydrocarbons. Notably 'Blue Ridge Mountains' More common over hardwood forests, less common over pine, lesser still over spruce, largely absent over grass. Probably reaches a peak between 80 and 90 F as thats when plant stomata are open widest.

  • Humidity. Higher humidity will make condensation more likely.

  • Dust. Fine dust itself is a light blocker, and also acts as condensation nuclei for water droplets.

  • Fire. Even distant fire can add significant haze especially if weather conditions are mixing high altitude air down to the surface. A nearby fire can turn the sun off.

  • Agricultural activity -- ploughing, harvesting -- increases dust in the air.

  • Dry weather. Increases dust, increases fire risk

  • Temperature inversions: Local dust/polution sources are trapped below the inversion layer.

  • Low temps combined with high humidity -- ice fog.

Factors that reduce haze:

  • Cold temperatures. Plants shut down.

  • Wet ground. Dust sticks.

  • Frozen ground. Less dust.

  • Snow on ground. Even less dust.

  • Strong winds, when otherwise no dust source. Tend to mix high altitude flows with surface air.

Local airports will report the visibility, and some stations will give forecasts of it. You may find that 'unlimited' is ok for pix but 'Visibility 5 miles' is not.

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    These all look like very good factors which could be used to predict haze - predictions don't have to be perfect. – Philip Kendall Jan 1 '18 at 8:55
  • Combining them all to come up with a valid 'haze forecast for next week' would be difficult. For an individual shutterbug, the knowledge of these may allow a choice of destinations on a marginal day. E.g. try upwind of the harvest, go to places where you are closer to your mountains. Knowing you have an inversion at 3000 feet may mean you will have clear skies at 4000 feet over a sea of white. – Sherwood Botsford Jan 1 '18 at 22:22

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