## June 13, 2018

### I Couldn't Think of a Pun about Potential Evapotranspiration

Hmmm. Maybe "PETs Allowed" would have worked.

Potential evapotranspiration is an important part of the Holdridge equation. Now that I have the temperature of the surface (suitably adjusted for lapse rate), I can derive the amount of water that's vaporizing from the surface. The easiest (and most inaccurate) way to figure that out is to use the Thornwaithe Equation:
$PET = 32 \left({10 T_a \over I}\right)^\alpha,$
where $T_a$ is the average temperature, $I$ is the heat index, and $\alpha$ is a factor derived from the heat index. All these are easily derived.

 July PET map (black is lower evaporation)
Man. I really need to fix the temperature maps - right now the map thinks it's got a massive ice cap that coats nearly the entire bottom fourth of the planet. That could make for some cool Clan of the Cave Bear type adventures. But it's not what I'm looking for.