Federal Aviation Administration.

An instrument developed by K. Angstrom for measuring the effective terrestrial radiation. It consists of four manganin strips, of which two are blackened and two are polished. The blackened strips are allowed to radiate to the atmosphere while the polishe ...

The mean difference between the readings of a given instrument and those of a standard instrument.

An accumulation of granular ice tufts on the windward sides of exposed objects that is formed from supercooled fog or cloud and built out directly against the wind.

Same as dropsonde.

A type of cooling-power anemometer based upon the principle that the time constant of a thermometer is a function of its ventilation.

Same as instrument shelter.

A type of precipitation composed of unbranched crystals in the form of needles, columns, or plates. Usually has a very slight downward motion and may fall from a cloudless sky.

See hydrologic accounting.

Precipitation composed of balls or irregular lumps of ice with diameters between 5 and 50 mm.

Force wind-Wind with a speed above 64 knots (73 mph); Beaufort scale numbers 12 through 17.

Snow shower, particularly of a very light and brief nature.

A thermometer using transducing elements which deform with temperature. Examples are the bimetallic thermometer and the Bourdon tube type of thennometer.

A clay atmometer consisting of a hollow ceramic sphere through which evaporation occurs. Evaporation is measured by the loss of water from the reservoir which feeds the sphere.

A thermometer used in aircraft which automatically corrects for adiabatic and frictional temperature rises by imparting a rotary motion to the air passing the thermal sensing element.

A sunshine recorder of the type in which the time scale is supplied by the motion of the sun. It consists of two opaque metal semi-cylinders mounted with their curved surfaces facing each other. Each of the semi-cylinders has a short narrow slit in its fl ...

Abbreviation for the pressure, temperature, and humidity data obtained by a radiosonde observation.

A line drawn through geographical points having the same duration of sunshine (or other function of solar radiation) during a given interval of time.

A graphical aid used in the reduction of data from a winds aloft observation.

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