A forecast of the expected stage or discharge at a specified time, or of the total volume of flow within a specified Interval of time, at one or more points along a stream.

The number of cycles per second between the limits of a frequency band.

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

The boundary between the troposphere and stratosphere, usually characterized by an abrupt change in lapse rate. Its height varies from 10 to 20 km. Regions above the tropopause have greater atmospheric stability than regions below.

An instrument which automatically records the voltage applied to it, as a function of time.

The water volume within a specified portion of a stream channel.

The length of air flow past a wind vane required for the vane to respond to 50 percent of a step change in wind direction. Expressed in feet or meters and calculated from delay time times wind tunnel speed.

The frequency of a carrier wave.

A method of upper air observation consisting of an evaluation of the wind speed and direction, temperature, pressure, and humidity aloft by means of a balloon-borne radiosonde tracked by radar or a radio theodolite.

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

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

A halo consisting of a faint white circle passing through the Sun and running parallel to the horizon for as much as 360

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.

The process of modifying some characteristic of a wave (the carrier) so that it varies in step with the instantaneous value of another wave (the modulating wave) in order to transmit a message. The modified characteristic may be frequency, phase, and/or a ...

Any one of numerous devices for the measurement of either speed alone or of both direction and speed (set and drift) in flowing water.

A clock-driven instrument mounting which automatically and continuously points in the direction of the sun. It is used with a pyrheliometera,hen continuous direct solar radiation measurements are required.

A technique for making winds aloft observations in which two theodolites located at either end of a baseline follow the ascent of a pilot balloon. Synchronous measurements of the elevation and azimuth angles of the balloon. taken at periodic intervals, pe ...

That temperature at which, in a specified latitude, the reading of a particular barometer requires no temperature or latitude correction.

The time required for an instrument to registe 63.2% of a step change in the variable being measured.

Same as evaporative power.