Weather Facts for Kids
Wild facts about weather
The polar vortex is a large area of cold, low-pressure air that circles the Arctic. When it weakens and splits, chunks of extremely cold Arctic air can spill southward into North America and Europe, causing sudden severe cold snaps.
The green flash is a rare optical phenomenon that sometimes appears at the very top of the Sun just as it sets below the horizon. It is caused by the atmosphere refracting different colours of sunlight by different amounts, with green becoming briefly visible on its own.
Hurricane Katrina, which struck New Orleans in August 2005, was one of the costliest natural disasters in US history. The storm surge flooded about 80% of the city, displacing over one million people from the Gulf Coast region.
Normally, air gets cooler as you go higher, but in a temperature inversion the opposite happens — a layer of warm air sits on top of cooler air near the ground. Inversions can trap pollution close to the surface, causing smog in cities on calm, clear days.
Thundersnow is a rare weather event where a thunderstorm produces heavy snowfall instead of rain. The thunder in a thundersnow storm sounds more muffled than normal because snow absorbs sound very effectively.
Ball lightning is a mysterious and rarely observed weather phenomenon in which glowing spheres appear during thunderstorms, lasting from a few seconds to several minutes before disappearing. Scientists still do not fully agree on what causes it.
An anemometer is the scientific instrument used to measure wind speed. The most common type has three or four cups that spin in the wind — the faster the wind, the faster the cups rotate, and the speed is calculated from the rotation rate.
The rain gauge is one of the oldest meteorological instruments, first developed in ancient India and Korea around the 15th century. In the 1400s, the Korean king Sejong had rain gauges distributed across the country to help plan farming.
A supercell is the most powerful and long-lived type of thunderstorm, containing a deep, rotating updraft called a mesocyclone. Supercells are responsible for producing the most violent tornadoes and the largest hailstones.
A rain shadow is a dry area on the downwind side of a mountain range. When moist air rises over the mountains, it cools and drops its rain on the windward side, leaving the other side dry — this is why deserts often form just behind mountain ranges.