I
Formation of ice or frost on an aircraft.
An elevation depressed below mean sea level by the amount equal to the sum of amplitudes of the four main harmonic constituents: M2, S2, K1 and O1. Also known as ISLW.
Aboriginal and Torres Strait Islander communities have seasonal calendars based on traditional weather, climate and environmental knowledge passed from generation to generation.
A method used to infer the amplitude and phase of constituents where a tidal data set has insufficient duration.
To separate a pair of constituents of similar frequency, you can infer the amplitude and phase of one member of the pair (generally the weaker) on the basis of an analysis of a longer data set from a nearby location or the equilibrium relationships.
The inference relationships between the two constituents must be accounted for in the analysis.
The Water Regulations 2008 separate water information into two types:
- historical – information a person holds before the end of the grace period
- new or ongoing – information that comes into a person's possession after the grace period has expired.
Regulation 7.04 lists certain subcategories of water information and person categories. An organisation listed in these person categories and holding these data during the grace period gives them as historical information. You give historical information within a fortnight after the end of the grace period.
New information is the information that comes into your possession after the grace period. You give new information at various specified timeframes on an ongoing/continuing basis.
Long-wave electromagnetic radiation which is emitted by all objects.
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.
A set of regulations governing all aspects of civil aviation aircraft operations when a flight is conducted using instruments rather than outside visual reference.
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.
Also called internal wave.
The ocean usually has a less dense upper layer overlying the much deeper, denser waters. Waves known as internal waves often occur on the interface between these two layers.
If the interface is gradual, the direction of wave propagation may have a vertical component, trapped by refraction within upper and lower limits.
Internal waves are usually caused by flow in the lower layer moving over an obstacle such as an undersea ridge. For example, semi-diurnal tidal flows into and out of a fjord. When this happens, a semi-diurnal internal wave, or internal tide, is produced.
Although these waves do not significantly affect the sea surface, they may be detected by satellite as bands of surface slicks due to the convergence of surface currents that are produced.
A hypothetical vertical distribution of atmospheric temperature, pressure and density that by international agreement is taken to be representative of the atmosphere for purposes of pressure altimeter calibrations, aircraft performance calculations, ballistic tables, etc.
The part on a beach or coastal zone that lies between high and low tidal levels. It is exposed or inundated depending on the tide.
The region where southeast and northeast trade winds meet, usually located between 10 degrees north and south of the equator. It is a broad area of low pressure, located in the southern hemisphere during our summer, and in the northern hemisphere during its summer.
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.
Measure of the rate of electromagnetic energy received per unit area.
Line on a weather map joining places with the same air pressure.