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

The change in barometric pressure within a specified period of time (typically 3 hours for meteorological observations).

Phase Shift Keying. A form of phase modulation of a data signal performed by a modem for transmission over dedicated wire or phone lines.

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

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

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

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 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.

Same as an upper air observation, but commonly used to refer to a single complete radiosonde observation.

An instrument for measuring snow hardness in terms of the resistance of snow to the pressure exerted by a disk attached to a spring-loaded rod, a gauge calibrated in pounds per square inch registers the amount of resistance. See Canadian hardness gauge.

A device, similar to a phytometer, for measuring transpiration. It consists of a small vessel containing water and sealed so that the only escape of moisture is by transpiration from a leaf, twig, or small plant with its cut end inserted in the water.

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.

One of several constant-pressure levels in the atmosphere for which a complete evaluation of data derived from upper air observations is required.

Same as ombrometer.

A type of electrical thermometer in which the thermal element is a substance whose electrical resistance varies with the temperature. Such thermometers can be made with very short time constants and are capable of highly accurate measurements.

See mote.

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 ...

A type of modulation in which the frequency of a continuous radio carrier wave is varied in accordance with the properties of a second (modulating) wave.

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

A unit of energy equal to 1.356joules.