A pyrheliometer of the thermoelectric type. Radiation is allowed to fall on two concentric silver rings, the outer covered with magnesium oxide and the inner covered with lamp black. A system of thermocouples (thermopile) is used to measure the temperatur ...

A rain gauge capable of measuring very small amounts of precipitation. Also called micropluviometer, trace recorder.

A seasonal wind of persistent direction, characterized by a pronounced change in direction between seasons.

A graduated scale placed in a position so that the stage of a stream may be read directly from it. Staff gauges may be placed on bridge piers or pilings, etc., or placed on specially constructed supports.

An instrument which measures the rate of evapotranspiration. It consists of a vegetation soil tank so designed that all water added to the tank and all water left after evapotranspiration can be measured.

The height at which the maximum wind speed occurs, determined in a winds-aloft observation.

The algebraic difference between the upper and lower limits of the measuring range of an instrument, i.e. a thermometer with a range of -35 to 50

A type of photoelectric photometer used to measure high-altitude winds on the assumption that stellar scintillation is caused by atmospheric inhomogeneities being carried along by wind near the tropopause level.

A rain gauge or array of rain gauges designed to measure the inclination and direction of falling rain.

A measure of the intrinsic luminous intensity emitted by a source in a given direction. Luminance is a measure only of light. The comparable term for electromagnetic radiation in general is radiance.

For a given location, a measure of the long-range effectiveness of precipitation in promoting plant growth. Also called precipitation-evaporation index.

The distance that an observer can see vertically into a surface-based obscuring phenomenon such as fog, rain, or snow. The distance estimate must be based upon ceiling balloon ascensions or ceiling light projector measurements.

The humidity transducinu element in a Diamond-Hinman radiosonde. Also called electrolytic strip.

A set of rules or conventions used to standardize data transfer between devices.

Downward scattered and reflected solar radiation, coming from the whole hemisphere with the exception of the solid angle of the sun's disc on a surface perpendicular to the axis of this cone.

Any source of radiant energy, especially electromagnetic energy.

An instrument for determining the dust content of a sample of air. Also spelled conimeter.

A radiosonde whose carrier wave is modulated by audio-frequency signals whose frequency is controlled by the sensing elements of the instrument.

See calorie.

The stage on a fixed river gauge at which it is necessary to begin issuing warnings or river forecasts if adequate precautionary measures are to be taken before flood stage is reached.