Saturday, March 18, 2017


From the US Geological Survey:
"Sublimation is the conversion between the solid and the gaseous phases of matter, with no intermediate liquid stage. . . 
Sublimation occurs more readily when certain weather conditions are present, such as low relative humidity and dry winds. Sublimation also occurs more at higher altitudes, where the air pressure is less than at lower altitudes. Energy, such as strong sunlight, is also needed. If I was to pick one place on Earth where sublimation happens a lot, I might choose the south face of Mt. Everest. Low temperatures, strong winds, intense sunlight, very low air pressure—just the recipe for sublimation to occur."
Since we got back to Anchorage March 1, we've had low temperatures, not much higher than 25˚F (-4˚C) during the day and sometimes down to -2˚F (-19˚C) at night.  Wind.  and lots of intense sunlight.  Wikipedia says that average air pressure at sea level is 1013.25 mbar.  The National Weather Service charts for the several days in Anchorage show air pressure gradually rising from a low 998.2 on the 15th up to 1014.9 early this morning (3/17/17) and dropping this evening down to 1008.4. So I'm guessing we have a lot of relatively low air pressure for the last two weeks as well.

Again from the USGS:
"In summary, energy is needed for the sublimation of ice to vapor to occur, and most of the energy is needed in the vaporization phase. A cubic centimeter (1 gram) of water in ice form requires 80 calories to melt, 100 calories to rise to boiling point, and another 540 calories to vaporize, a total of 720 calories. Sublimation requires the same energy input, but bypasses the liquid phase."

Here's what that snow berm looked like a week ago, after the snow plows went through.

It's hard not to see everything as a metaphor these days.  Sublimation might well describe what would happen to many US government science programs - like those agencies that provided the weather data in this post and the definition of sublimation - if Trump's budget were to pass.  Many of the programs would pass from a solid to a gas, skipping the liquid stage.  And the top picture of the ragged wall of snow might serve as a good metaphor for what many agencies would look like.

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