An instrument for determining the direction from which radio waves approach a receiver. It may consist of a manually operated direction indicator, or it may use a servo system to position the antenna automatically in the direction of the incident waves. T ...

An instrument which measures the spectral distribution of the intensity of direct solar radiation.

To free something from the binding action of ice by warming it to a temperature above the melting point of ice. Also, a warm spell when ice and snow melt.

Barometer in which pressure is determined by balancing air pressure against the weight of a column of mercury in an evacuated glass tube.

Downward-facing pyranometer used for measuring reflected solar radiation.

An instrument for measuring the difference of the solar radiation falling on both sides of a horizontal surface from the whole hemisphere.

Abbreviation for mean sea level.

An instrument for measuring radiant energy. See actinometer, Dines radiometer, photometer, Tulipian radiometer.

Same as photometer.

A weakly colored lunar halo identical in form and optical origin to the solar parhelion.

A form of data transmission in which the bits of each character are all sent simultaneously, resulting in extremely fast communication but requiring a communication path for each bit. Compare to serial data transmission.

The actual time during which physical events take place.

An instrument for measuring the extinction coefficient in water.

National Centers for Environmental Prediction. Central computer and communications facility of the National Weather Service; located in Washington, DC.

An instrument for measuring the difference between incoming and outgoing terrestrial radiation.

A photometric unit of illuminance or illumination equal to one lumen per square meter

A device used to hold liquid-in-glass maximum and minimum thermometers in the proper recording position inside an instrument shelter, and to permit them to be read and reset. See Townsend support.

A local variation of the wind vector or any of its components in a given direction.

The measurement and computation of wind speeds and directions at various levels above the surface of the earth. Methods include pilot balloon observations, rabals, rawin or rawinsonde observations, radar tracking, or acoustic sounding.

Value of soil moisture, expressed as a percentage of the mass of dry soil, below which a plant living in the soil dies by wilting.