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.

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

A pyrheliometer of the bimetallic type used to measure the intensity of direct solar radiation.

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

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.

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

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.

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

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

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.

A type of recording siphon barometer. The mechanically magnified motion of a float resting on the lower mercury surface is used to record atmospheric pressure on a rotating drum.

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

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

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 ...

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

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

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

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 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.