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 ...

A scale of yellows, greens, and blues for recording the color of sea water, as seen against the white background of a Secchi disk.

Generally, the relative states of inflow, outflow, and storage of moisture over a given area of earth's surface.

Same as pitot tube.

A unit of illuminance or illumination equal to one lumen per foot'. This is the illuminance provided by a light source of one candle at a distance of one foot.

Radiation with wavelengths greater than 4 microns. (In meteorology, same as infrared radiation.)

The total electromagnetic radiation emitted by the sun. About 99.9 percent of its energy output falls within the wavelength interval from 0. 15 microns to 4.0 microns, with peak intensity near 0.47 microns. About one-half of the total energy in the solar ...

A mercury barometer arranged so that the position of the upper or lower meniscus may be measured photographically. In one design the image of the meniscus is formed on a rotating drum covered with sensitized paper so that a continuous record of pressure a ...

Frozen or partly frozen rain.

A recording siphon barometer.

A local variation in the wind direction or speed. This condition can present danger to aircraft, especially at landing, when a sudden shift from headwind to tailwind can cause a rapid loss of airspeed and lift.

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

Tables prepared from the psychrometric formula and used to obtain vapor pressure, relative humidity, and dew point from values of wet-bulb and dry-bulb temperatures.

The line-of-sight distance between two objects.

Same as rain gauge.

modulated radiosonde-A radiosonde which transmits the indications of the meteorological sensing elements in the form of pulses spaced in time. The meteorological data are evaluated from the intervals between the pulses. Also called timeinterval radiosonde ...

Precipitation of very small, white opaque particles of ice, fairly flat or elongated, with diameters less than 1 mm. The solid equivalent of drizzle.

A set of rules or conventions used to standardize data transfer between devices.

Atmospheric layer throughout which there is no change of temperature with height, i.e. a zero lapse rate.

See radiation shield.