January 11: Summit Weather
- High temp: 5 F
- Low temp: -2 F
- Average Wind Speed: 46.7 mph gusting to 72 mph
A foggy day with visibility down to 1/16th of a mile. The observatory reported zero hours of sunshine for the day. Perfect conditions for rime ice. We could hardly step outside without it accumulating on our clothes and, of course, our gear.
I brought out my contact mics to record the sound of rime accumulating on them. The best spot I found was attaching them to the windward side of a wooden sign post. Here’s an excerpt:[audio:rime_accumulation.mp3]
Listening to the entire recording one can clearly hear the frequency of the resonant ping sounds increase as more ice accumulates. I suspect the ice accumulation reduces the surface area of the contact mic or otherwise stiffens the transducer–in a manner similar to a drummer increasing the pressure on a drum head and thus causing the pitch to rise.
Here’s a recording of an ice-covered chain squeaking in the wind. The squeak is less metallic than I expected, sounding more like rubbing ice cubes together.[audio:squeaky_chain.mp3]
Here’s a photo of the chain (taken on another, much sunnier day). Yes, this chain appears to be preventing the building from blowing off the mountain. The story I heard is that the chains were an important part of the original building. When they rebuilt the structure, chains were included as an historical and decorative element. There were times when I could have used a chain or two to prevent me from blowing away.