Wednesday, November 30, 2011

Clear air

Recently, there was a major front that passed over. Fronts are like air vacuums, cleaning the air. This happens because the dust in the air either forms cloud droplets or are absorbed by cloud droplets, the front then moves away with the dust or sends it back to the ground by rain. This is what happened, and the air is very clean. How can you tell? Usually there is an aureole around the sun by larger particles scattering light forward. It is typically a couple degrees wide, but if there is little or no aureole it means the air is really clean. In places in Antarctica or up above cirrus clouds, the effect is very striking.


  1. Good post, Nick. It's frightening to think how few of this type of day we get here in the BHT. Love the lamppost! Check out my latest post. We have similar gas lamps here at school!

  2. Yeah, Jacksonville is located right below a band of high pressure, the same band that makes North Africa such a dry desert wasteland, but Florida is too tropical to be a desert. Unfortunately England is right below a low pressure band, making good rainy weather!
    Also, I believe these lamps are sodium vapor lamps, its fun to look at the spectrum with all the lines in it. That lamp's been good to me. Behind it is a tree that aligns with it to be exactly north, and it serves as a great sun blocker!

  3. The lamps at school are also sodium vapour, but were originally gas lamps. You can still occasionally see old gas lamp conversions here in the UK, though they are becoming quite rare these days. The last one in my neighbourhood disappeared about ten to fifteen years ago.
    One thing that I like about the weather here in England is that it is very varied. Okay, so it may be wetter than average, but I would sooner trade that off for the variety!

  4. The neighborhood where I live is fairly new, made in the 1990s, so I don't think we've ever had gas lamps. I also like varied weather. I'm a fan of clear skies, overcast, partly cloudiness, it's all good to me. Its always good to enjoy an overcast day!