The visibility along an identified runway, determined from a specified point on the runway with the observer facing in the same direction as a pilot using the runway. Compare to runway visible range.

A number of quantity defining a limit that errors will not exceed when a device is used under specified operating conditions. Accuracy rating can be expressed in a number of forms, i.e. in terms of the measured variable (+/- 1 C), percent of span (+/-0.5% ...

The cardinal points of the compass, i.e. north, south, east, west.

The unit of speed in the nautical system; one nautical mile per hour. It is equal to 1.1508 statute miles per hour or 0.5144 meters per second.

The programs and instructions which direct a computer.

The limiting values of ceiling, visibility, and wind, or runway visual range, established as safety minimum for aircraft landings and take-offs.

The transducer of any hygrometer, i.e. that part of a hygrometer that quantitatively "senses" atmospheric water vapor.

Same as atmometer.

A numbering system using a base number of 16 and including the ten decimal digits (0 to 9) along with six alpha digits (A to F). Thus. a digit is available to represent each of the possible values of a 4-bit binary digit.

Difference between the temperatures of the dry-bulb and the wet-bulb thermometers of a psychrometer.

Operation mode of a communication circuit in which one end can only transmit and the other end can only receive.

Electromagnetic radiation of shorter wavelength than visible radiation but longer than x-rays, between 0.02 and 0.4 micron (200 and 4000 angstrom).

Abbreviation for radio frequency.

A balloon-borne instrument for the simultaneous measurement and transmission of meteorological data. It includes transducers for the measurement of pressure, temperature, and humidity; a modulator for the conversion of the output of the transducers to a q ...

A form of psychrometer with wet-bulb and dry-bulb thermometers mounted on opposite sides of a specialty designed graph of the psychrometric tables. It is so arranged that the intersections of two curves determined by the wet-bulb and dry-bulb readings -yi ...

A subtle, diumal component of the wind velocity leading to a diumal shift of the wind or turning of the wind with the sun, produced bv the east-to-west progression of daytime surface heating.

In a radiosonde observation, a level (other than a standard level) for which values of pressure, temperature, and humidity are reported because temperature and/or humidity data at that level is sufficiently important or unusual to warrant the attention of ...

See evaporative opportunity.

A hypothetical "body" whose surface absorbs no electromagnetic radiation of any wavelength. An idealization exactly opposite to that of the black body. In nature, no true white bodies are known. Moist white pigments exhibiting high reflectivity for visibl ...

See hydrologic accounting.