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

A method of winds aloft observation in which the elevation and azimuth angles of a theodolite are read while visually tracking a pilot balloon. Balloon height data is estimated from assumed balloon ascension rates.

See stage.

An instrument for measuring the relative speed of a fluid. It consists of a concentric pipe arrangement in which the inner pipe is open at one end and the outer pipe is perforated and closed at both ends. Each pipe is connected to a manometer. The unit is ...

A mercury barometer in which the tube is U-shaped and the upper and lower mercury surfaces have the same diameter.

The temperature at which the liquid and solid forms of a substance may exist in equilibrium at a given pressure (usually one standard atmosphere). The true freezing point of water is known as the ice point.

The amount of sky covered or concealed by clouds or obscuring phenomena. It is reported in tenths, so that 0.0 indicates a clear sky and 1.0 (or 10/10) indicates a completely covered sky. The following classifications are used in aviation weather observat ...

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

Wind with a speed between 28 and 33 knots (32 and 38 mph); Beaufort scale number 7.

Lowest altitude in the atmosphere over a given location at which the air temperature is 0

In aviation terminology, route or terminal weather conditions of sufficiently low visibility to require the operation of aircraft under instrument flight rules.

A faintly-colored circular arc similar to a rainbow but formed on fog layers containing drops whose diameters are 100 microns or less. Also called mistbow, white rainbow.

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

Solar radiation of selected wavelengths.

Precipitation composed of white or translucent ice crystals, chiefly in complex branched hexagonal forms.

Determination of the total amount of snow covering a watershed or a given region. Both depth and water content of the snow may be measured, and the results may be used to predict the amount of water that will be available after melting.

A rain gauge which is placed under trees or foliage to determine the rainfall in that location. By comparing this catch with that from a rain gauge set in the open. the amount of rainfall which has been intercepted by foliage can be determined.

Diffuse solar radiation which has the same intensity in all directions.

Pertaining to rain, or more broadly, to precipitation.

Apparatus from which the nature and time of precipitation may be determined.