Comprehension: Geographical Peculiarities of Tropical Islands

          Residents on tropical islands come to expect a cumulus cloud to form above each island by mid-morning. Often it transforms to the cumulonimbus type and cools the bit of land with a hard shower by mid-afternoon. Afterwards, the cloud is a cumulus once again, seemingly tethered above the island by an invisible cord which snaps at sunset. Then the cloud drifts away and vanishes. So regular are these events that airlines try to schedule plane services for early morning or sunset hours when the sky will be clear and the landing fields dry. While a cumulus or cumulonimbus cloud hangs about the island, turbulent air can be predicted, and rough landings with accidents are likely.

          These changes give the evidence that the morning sun routinely warms the land faster than the sea around it, and starts as an upward movement of heated, lighter air. To take its place, moisture-laden breezes blow onshore from all sides. This air, in turn, is heated and rises. Soon it reaches cooler heights where the atmosphere pressure is less, and mist forms. The cloud of condensed droplets may have its base only two kilometres above sea level, but by afternoon the rising column may project into the stratosphere as a great pillar as much as 2,500 meters high. Usually, the atmospheric winds cut away the top of the pillar, keeping it flat there or even anvil-shaped.

– Adapted from NOSEC Book Six.