Drycrest: Precipitable Water Vapour
Cosmology & the Sky arc, page 162 of 193. Back to The Pixelated Physics Universe
Who they are
Drycrest has one line, and says it often: “Above the water. not above the deadline.”
Drycrest is a character of the Cosmology & the Sky arc: drawn in pixels, ruled by one piece of real physics, and never allowed to break it.
The physics
High sites are chosen for low precipitable water vapour; in situ TMT site testing gave median PWV of 1.86 mm at Mauna Kea 13N (4050 m) and 1.70 mm at Cerro Tolonchar (4480 m).
$$ \begin{gathered} \text{PWV} = \frac{1}{\rho_w g}\int_0^{p_s} q\, dp \\ \text{median PWV} \approx 1.86\ \text{mm (Mauna Kea 13N)} \end{gathered} $$
| Symbol | Meaning | SI unit |
|---|---|---|
| $\text{PWV}$ | precipitable water vapour | m |
| $\rho_w$ | density of liquid water | kg/m^3 |
| $g$ | gravitational acceleration | m/s^2 |
| $q$ | specific humidity | — |
| $p$ | pressure | Pa |
| $p_s$ | surface pressure | Pa |
Sources
Crossovers
Drycrest meets Nimbryn (Mie Scattering Clouds). Nimbryn's clouds block all wavelengths. Drycrest's water vapour absorbs specific infrared and submillimetre bands. Both are reasons observatories are built high and dry.
Drycrest meets Summitbrew (Boiling Point at Altitude). Drycrest chooses mountain sites for their dry air. Summitbrew lives up there too, where water boils near 86–87 °C.
Wear the lore
Concept keywords: Precipitable Water Vapour, Drycrest, Cosmology & the Sky, physics lore, Pixelated Physics