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

variable audio-modulated radiosonde developed at the Bureau of Standards and used by the United States weather services.

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.

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

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

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.

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.

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.

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

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.

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.

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

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

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 ...

An atmometer which uses a filter paper disc as the evaporating element. The amount of water evaporated through the paper is read at the graduated tube reservoir.

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 ...