I
Formation of ice or frost on an aircraft.
Aboriginal and Torres Strait Islander communities have seasonal calendars based on traditional weather, climate and environmental knowledge passed from generation to generation.
Coastal waters from the coast to 12 nautical miles out.
Solar radiation or heating received at the Earth’s surface. The name comes from INcoming SOLar radiATION.
State of the atmosphere where a parcel of air continues rising, after the lifting mechanism stops. Air parcels can begin to rise in many situations. These include:
- due to daytime heat
- ahead of an approaching cold front
- when airflows converge, as in a low pressure system.
Instability can lead to thunderstorms.
Light
Up to 0.2 mm an hour. Can be felt on the face but is not visible. Produces little run-off from roads or roofs. Visibility is reduced, but not less than 1 km.
Moderate
0.2–0.4 mm an hour. Window and road surfaces streaming with moisture. Visibility generally between 400 m and 1 km.
Thick or heavy
Over 0.4 mm an hour. Visibility reduced to less than 400 m.
Light
Sparse hailstones, often mixed with rain.
Moderate
Enough hailstones that the ground looks white.
Heavy
Thick coverage of hail on the ground and it may pile up in drifts or against buildings.
Light
Up to 2 mm an hour. Individual drops easily identified, puddles form slowly, small streams may flow in gutters.
Moderate
2.2–6 mm an hour. Rapidly forming puddles, down-pipes flowing freely, some spray visible over hard surfaces.
Heavy
6.2–50 mm an hour. Falls in sheets, misty spray over hard surfaces, may cause roaring noise on roof.
Violent
More than 50 mm an hour. Gutters and downpipes overflowing, spray to a height of several centimetres over hard surfaces and may cause roaring noise on roof.
Light
Gives a water equivalent of up to 2 mm an hour.
Moderate
Gives a water equivalent of 2.2–6 mm an hour.
Heavy
Gives a water equivalent of more than 6 mm an hour.
Flood. Overflow of water onto land from rainfall, rivers or raised sea levels.
When air temperature increases with height. (Generally, air cools with height.) Low-level inversions can form on clear, calm nights as the ground radiates (loses) the heat it absorbed during the day. The warm air on the ground is replaced by cooler air. The inversion creates a boundary layer that restricts mixing between the air masses. Inversions act like a lid, trapping pollutants and causing smog over cities.
Line on a weather map joining places with the same air pressure.