9-1/2 x 9"
Pen & ink, watercolor |
CumulusCumulus: a heap, a pile, an accumulation . . . -OED Ordinary cumulus clouds look solid and still, with their flat bottoms resting on a glass floor overhead. In fact, clouds are no more solid than fog (a cloud on the ground), and exist in a steady state of simultaneous construction and destruction. A cumulus cloud forms when a bubble of warmed air rises from warm ground. The air cools as it rises until its temperature drops to the dew point — the point at which its water vapor will condense into water droplets. Where the water condenses, the cloud begins, establishing the height of the imaginary floor the cloud seems to rest on. The cloud builds as condensation releases the energy that had kept the water in an evaporated state — the energy becomes heat, the heat warms the air, and the air continues to rise until there is no more water to condense. At this point, the cloud stops growing. The warmed air does its rising through the center of the cloud, forming the hard-looking cauliflower top — “one could fancy hacking hard chips off with a hatchet,” said Virginia Woolf — where the condensation takes place. Then the dried-out air moves out from the center and sinks in a cold downdraft, warming as it descends, eating into the cloud with its warmth, and leaving the cloud’s lower sides torn and ragged — always a work in progress. |