A record obtained from a meteorograph. A chart in which meteorological variables are plotted against time.

A type of anemometer in which the rotation of an element serves to measure the wind. Rotation anemometers are divided into two classes; those in which the axis of rotation is horizontal, such as the windmill anemometer, and those in which the axis of rota ...

The time required for an instrument to registe 63.2% of a step change in the variable being measured.

A liquid-in-glass thermometer which uses an organic substance such as alcohol as the thermometer liquid. This type of thermometer has a low freezing point and a high coefficient of expansion. It is less accurate, however, than a mercury thermometer.

Thermometer for measuring the temperature in the soil at different depths.

An instrument for measuring the ultraviolet in solar and sky radiation.

An evaporation pan in which the evaporation is measured from water in a pan floating in a larger body of water.

Very small precipitation drops (diameters less than 0.5 mm) that appear to float with air currents while falling in an irregular path. Unlike fog droplets, drizzle falls to the ground.

Winds which, over a small area, differ from those which would be appropriate to the general pressure distribution.

A mercury-in-glass thermometer which records the temperature upon being inverted and retains its reading until being returned to the first position.

A device for measuring the river stage. Also called stream gauge.

A faintly-colored circular arc similar to a rainbow but formed on fog layers containing drops whose diameters are 100 microns or less. Also called mistbow, white rainbow.

Sustained winds greater than or equal to 40 mph or gust greater than or equal to 58 mph.

A general term for atmospheric water in any of its forms, i.e. clouds, fog, hail, ice crystals, rain.

A forecast of the expected stage or discharge at a specified time, or of the total volume of flow within a specified Interval of time, at one or more points along a stream.

Any and all forms of water particles, liquid or solid, that fall from the atmosphere and reach the ground.

The closeness of agreement among measurements of the same value of the same quantity where the individual measurements are made under different defined conditions, i.e. by different methods or with different measuring instruments.

An instrument for measuring the relative speed of a fluid. It consists of a concentric pipe arrangement in which the inner pipe is open at one end and the outer pipe is perforated and closed at both ends. Each pipe is connected to a manometer. The unit is ...

A relatively small-scale, downward moving current of air.

By international agreement, a period during which greatly increased observation of world-wide geophysical phenomena is undertaken through the co-operative effort of participating nations. July 1957-December 1958 was the first such year. However, precedent ...