Glossary
63 words used in the lessons.
- Air pressure
- The weight of the air above a place. Air flows from high towards low pressure and is turned by the Earth's spin. Learn more: Wind
- Anomaly
- The difference between a value and the long-term average for the same place and time of year. Learn more: Sea temperature
- Atomic clock
- A clock that counts the vibrations of atoms. Navigation satellites carry several, accurate to billionths of a second. Learn more: Satellites
- Aurora
- Light in the night sky made when charged particles from the Sun hit gases 100 to 300 km up. The northern lights are the aurora borealis, the southern lights the aurora australis. Learn more: Aurora
- Axial tilt
- The 23.4° angle between the Earth's spin axis and a line upright to its orbit. It causes the seasons. Learn more: Day, night and the seasons
- Beaufort scale
- A scale of wind strength from 0 (calm) to 12 (hurricane force), based on what the wind does to the sea and the land. Learn more: Wind
- Climate
- The usual pattern of weather at a place, described by averages over 30 years or more. Learn more: Climate zones
- Coriolis effect
- The turning of moving air and water caused by the Earth's spin: to the right in the northern hemisphere, to the left in the southern. Learn more: Wind belts
- Daily temperature range
- The difference between the warmest and the coldest temperature in a day. Learn more: Temperature
- Declination
- The angle between true north and the direction a compass points at a given place. Learn more: Earth's magnetic field
- Earthquake
- Shaking caused by a sudden slip of rock along a fault, releasing strain built up over years. Learn more: Events
- El Niño
- A warming of the central and eastern tropical Pacific, lasting about a year, that shifts weather around the world. Learn more: El Niño and La Niña
- Epicentre
- The point on the surface directly above where an earthquake starts. Learn more: Events
- Equinox
- One of the two days, around 20 March and 23 September, when the Sun is overhead at the equator and day and night are nearly equal everywhere. Learn more: Day, night and the seasons
- Forecast cone
- The area where the centre of a tropical cyclone will probably go, widening with time because forecasts get less certain. Learn more: Storms
- Free fall
- Moving under gravity alone. Astronauts float because they and their station fall together. Learn more: Satellites
- Geostationary orbit
- An orbit 35,786 km above the equator that takes exactly as long as the Earth's spin, so the satellite stays over one point. Learn more: Satellites
- Ground track
- The line on the Earth's surface directly beneath a satellite's path. Learn more: Satellites
- Gust
- A short burst of wind, lasting a few seconds, that is stronger than the average speed. Learn more: Wind
- Heat capacity
- How much heat a material needs to warm up. Kilogram for kilogram, water needs four to five times more than dry soil or rock. Learn more: A city's year
- Hot spot
- A place where unusually hot rock rises from deep in the mantle and feeds volcanoes far from plate boundaries, such as Hawaii. Learn more: Volcanoes
- Hypocentre
- The point underground where an earthquake starts. The epicentre is the point on the surface directly above it. Learn more: Events
- Intensity
- How strongly the ground shakes at one place. It depends on magnitude, distance, depth and the local ground. Learn more: Events
- Intertropical Convergence Zone
- The belt near the equator where the trade winds meet and moist air rises into thunderstorms. Also called the doldrums. Learn more: Wind belts
- Isobar
- A line on a weather map joining places with the same air pressure. Learn more: Highs, lows and isobars
- Köppen classification
- A system that sorts climates into zones by average temperature and rainfall, devised by the climatologist Wladimir Köppen around 1900 and refined since. Learn more: Climate zones
- Kp index
- A number from 0 to 9 that measures how disturbed the Earth's magnetic field is over three hours. Kp 5 and above is a geomagnetic storm. Learn more: Aurora
- Kuroshio
- A warm current that flows north past the east coast of Taiwan towards Japan, carrying tropical heat. Learn more: Sea temperature
- La Niña
- A cooling of the central and eastern tropical Pacific, the opposite of El Niño. Learn more: El Niño and La Niña
- Landslide
- A mass of rock, soil or mud sliding down a slope, often set off by heavy rain or an earthquake. Learn more: Storms
- Lapse rate
- How fast the air temperature falls with height: about 6.5 °C per kilometre on average. Learn more: Temperature
- Long-term average
- Values averaged over many years, usually 30, such as 1991–2020. They describe what is typical, not today. Learn more: Climate zones
- Magma
- Molten rock below the ground. Once it erupts at the surface it is called lava. Learn more: Volcanoes
- Magnetic field
- The region around the Earth where magnetic forces act. A compass lines up with it. Learn more: Earth's magnetic field
- Magnitude
- A single number for the size of an earthquake. Each whole step is about 32 times more energy. Learn more: Events
- Mantle
- The thick layer of hot, solid rock between the crust and the core. Over millions of years it flows very slowly. Learn more: Tectonic plates
- Mid-ocean ridge
- An underwater mountain chain where two plates move apart and new seafloor forms from rising molten rock. Learn more: Tectonic plates
- Monsoon
- A wind that reverses with the seasons because land and sea heat up and cool down at different rates. Learn more: Winds through the year
- Ocean current
- A steady flow of sea water, driven by winds and differences in temperature and saltiness. Learn more: Sea temperature
- Orbit
- The path of a satellite falling around the Earth while moving sideways fast enough to keep missing it. Learn more: Satellites
- Outer core
- The layer of liquid iron and nickel about 2,900 to 5,150 km below the surface, whose motion makes the magnetic field. Learn more: Earth's magnetic field
- P-wave
- The fastest earthquake wave, a push-and-pull wave that travels at about 6 km a second in the crust and arrives first. Learn more: Events
- Plate boundary
- The edge where two plates meet. Plates move apart at ridges, towards each other at subduction zones and collisions, and past each other at transform faults. Learn more: Tectonic plates
- Ring of Fire
- The belt of subduction zones, volcanoes and earthquakes that surrounds most of the Pacific Ocean. Learn more: Volcanoes
- S-wave
- A slower earthquake wave that shakes the ground from side to side, at about 3.5 km a second in the crust. It brings most of the strong shaking. Learn more: Events
- Sea surface temperature
- The temperature of the top layer of the sea, measured from satellites, ships and buoys. Learn more: Sea temperature
- Slab
- The part of a plate that has sunk into the mantle at a subduction zone. Learn more: Tectonic plates
- Solar wind
- The stream of charged particles that flows out from the Sun all the time, at hundreds of kilometres a second. Learn more: Aurora
- Solstice
- One of the two days, around 21 June and 21 December, when the noon Sun is overhead at one of the tropics and days are longest in one hemisphere. Learn more: Day, night and the seasons
- South Atlantic Anomaly
- A region over South America and the South Atlantic where the Earth's magnetic field is unusually weak. Learn more: Earth's magnetic field
- Subduction
- One plate sinking beneath another into the mantle. It makes ocean trenches, volcano chains and the largest earthquakes. Learn more: Tectonic plates
- Tectonic plate
- A huge rigid slab of the Earth's crust and uppermost mantle. About a dozen large plates and many small ones cover the planet and move a few centimetres a year. Learn more: Tectonic plates
- Trade winds
- Steady winds blowing towards the equator from about 30° north and south: from the north-east in the northern hemisphere and the south-east in the southern. Learn more: Wind belts
- Transform fault
- A boundary where two plates slide past each other sideways, such as the San Andreas Fault. Learn more: Tectonic plates
- Tropics of Cancer and Capricorn
- The lines at 23.4° N and 23.4° S, the furthest north and south that the Sun is ever directly overhead. The Tropic of Cancer crosses Taiwan. Learn more: Day, night and the seasons
- Tsunami
- A series of very long sea waves caused by a sudden movement of the seafloor, usually in a large undersea earthquake. Learn more: Events
- Typhoon
- A tropical cyclone in the north-west Pacific. Internationally the name is used once sustained winds reach 118 km/h; Taiwan's Central Weather Administration already calls a storm a (mild) typhoon from 62 km/h. The same kind of storm is a hurricane in the Atlantic and a cyclone in the Indian Ocean. Learn more: Storms
- Upwelling
- Cold, nutrient-rich water rising from below where the wind pushes surface water away from a coast. Learn more: Sea temperature
- Volcano
- An opening in the Earth's crust where magma, gas and ash reach the surface, and the mountain built around it. Learn more: Volcanoes
- Weather radar
- An instrument that sends out microwave pulses and measures the echoes from rain, snow and hail to map where precipitation is falling. Learn more: Rain
- Westerlies
- Winds from the west between about 30° and 60° latitude, which carry storms across the oceans. Learn more: Wind belts
- Windward and lee
- The windward side of a mountain faces the wind and gets the rain; the lee side is sheltered and drier. Learn more: Rain
- Yearly temperature range
- The difference between the average temperatures of the warmest and the coldest month. Learn more: A city's year