Monthly Image: Frost Growth

The northeast vent on the well pit grew an ice rim during the same night that frosted the roofing nails:

Well Pit Vent Frost

Well Pit Vent Frost

The other vent remained clear, so the prevailing breeze definitely goes in one hole and out the other:

Well Pit Vent Frost - inlet

Well Pit Vent Frost – inlet

Well Pit Vent Frost – inlet

A waterproof Hobo datalogger hangs from the string.

  1. #1 by Vedran on 2016-02-15 - 08:35

    Do you think it’s possible that the string served as a kernel for frost formation?

    • #2 by Ed on 2016-02-15 - 09:14

      I think not, because the frost grows symmetrically around the pipe.

      Yesterday, the IR thermometer reported 19 °F below the “inlet” pipe and 29 °F below the “outlet” pipe, so the pit really does vent the way I expected: the frost shows where moist air condenses. That’s way cold for a pit with a water pipe in mid-air, so I plugged the vents to see how the ground temperature stabilizes.

      It’s been that way for over half a century, though, so if the pipe hasn’t frozen yet, it probably won’t; this is mostly curiosity.