Wild Weather - February 2012

Did You Know? - A storm (Proto-Germanic *sturmaz "noise, tumult") is any disturbed state of an astronomical body's atmosphere, especially affecting its surface, and strongly implying severe weather. It may be marked by strong wind, hail, thunder and/or lightning (a thunderstorm), heavy precipitation (snowstorm, rainstorm), heavy freezing rain (ice storm), strong winds (tropical storm, hurricane, windstorm) or wind transporting some substance through the atmosphere (as in a dust storm, blizzard, sandstorm, etc.).

Did You Know? - Storms are created when a center of low pressure develops, with a system of high pressure surrounding it. This combination of opposing forces can create winds and result in the formation of storm clouds, such as the cumulonimbus. Small, localized areas of low pressure can form from hot air rising off hot ground, resulting in smaller disturbances such as dust devils and whirlwinds.

These storms occur when high levels of condensation form in a volume of unstable air that generates deep, rapid, upward motion in the atmosphere. The heat energy creates powerful rising air currents that swirl upwards to the tropopause. Cool descending air currents produce strong downdraughts below the storm. After the storm has spent its energy, the rising currents die away and downdraughts break up the cloud. Individual storm clouds can measure 2–10 km across.

Did You Know? - A rainbow is an optical and meteorological phenomenon that causes a spectrum of light to appear in the sky when the Sun shines on to droplets of moisture in the Earth's atmosphere. It takes the form of a multicoloured arc. Rainbows caused by sunlight always appear in the section of sky directly opposite the sun.

Did You Know? - The rainbow is not located at a specific distance, but comes from any water droplets viewed from a certain angle relative to the Sun's rays. Thus, a rainbow is not a physical object, and cannot be physically approached. Indeed, it is impossible for an observer to manoeuvre to see any rainbow from water droplets at any angle other than the customary one of 42 degrees from the direction opposite the Sun.

Even if an observer sees another observer who seems "under" or "at the end" of a rainbow, the second observer will see a different rainbow further off-yet, at the same angle as seen by the first observer.

Did You Know? - A rainbow spans a continuous spectrum of colours—there are no "bands". The apparent discreteness is an artefact of the photopigments in the human eye and of the neural processing of our photoreceptor outputs in the brain. Because the peak response of human colour receptors varies from person to person, different individuals will see slightly different colours, and persons with colour blindness will see a smaller set of colours. However, the seven colours listed below are thought to be representative of how humans everywhere, with normal colour vision, see the rainbow.