A measure of long-term precipitation effectiveness. The ratio of the normal annual rainfall to the normal annual evaporation.

A magnetometer of the electromagnetic type which is used to measure the horizontal intensity of the earth's magnetic field.

See photometer.

A photometer which measures the intensity of radiation as a function of the frequency (or wavelength) of the radiation.

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

An atmometer which uses a filter paper disc as the evaporating element. The amount of water evaporated through the paper is read at the graduated tube reservoir.

A buoyant balloon rising freely in the atmosphere, as opposed to a captive balloon.

Same as parhelion.

A type of modulation in which the frequency of a continuous radio carrier wave is varied in accordance with the properties of a second (modulating) wave.

A line of equal or constant temperature.

An addition to a rawinsonde system which allows determination of the slant range to the radiosonde.

The total amount of water transferred to the atmosphere by evapotranspiration.

A rotation anemometer which has a horizontal axis upon which helicoidal shaped vanes are mounted. See windmill anemometer.

A type of electrical thermometer in which the thermal element is a substance whose electrical resistance varies with the temperature. Such thermometers can be made with very short time constants and are capable of highly accurate measurements.

An effect noted primarily in wet snow conditions when snow clings to the sides of a precipitation gauge and gradually accumulates until the gauge orifice is capped with accumulated snow. This effect can be minimized by using large collectors, and wind scr ...

A graphical representation of stage or discharge at a point on a stream as a function of time.

A thermopile used in some types of radiation instruments. See solarimeter.

A warm, dry wind on the lee side of a mountain range, the warmth and dryness due to adiabatic compression upon descent.

A radiosonde which is dropped by parachute from an aircraft for the purpose of obtaining soundings of the atmosphere below.

A device for computing certain psychrometric data, usually the dew point and the relative humidity, from known values of the dry-bulb and wet-bulb temperatures and the atmospheric pressure. One type is the circular slide-rule form and, like the psychromet ...