The atmospheric pressure at mean sea level either directly measured by stations at sea level or empirically determined from the station pressure and temperature by stations not at sea level. Used as a common reference for analyses of surface pressure patt ...

A device for measuring the height of tide. It may be simply a graduated staff in a sheltered location where visual observations can be made, or it may consist of an elaborate recording instrument (sometimes called a marigraph) making a continuous graphic ...

Temperature of equilibrium between the liquid and vapor phases of a substance at a given pressure.

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.

Old snow that has become granular and compacted as a result of melting and refreezing.

A weakly colored lunar halo identical in form and optical origin to the solar parhelion.

See approximate absolute temperature scale, Celsius temperature scale, centigrade temperature scale, Fahrenheit temperature scale, Kelvin temperature scale, Rankine temperature scale, Reaumur temperature scale,

Companion to the wet-bulb thermometer in a psychrometer. Used to measure ambient air temperature.

A clock-driven device for recording the time of occurrence of an event or the time interval between the occurrence of events.

The condition of the atmosphere when the amount of water vapor present is the maximum possible at the existing temperature.

The standard deviation (positive square-root of the variation) of the errors associated with physical measurements of an unknown quantity, or statistical estimates of an unknown parameter or of a random variable.

The state of the atmosphere, mainly with respect to its effects upon life and human activities. As distinguished from climate, weather consists of the short-term (minutes to months) variations of the atmosphere.

An instrument for measuring radiant energy. See actinometer, Dines radiometer, photometer, Tulipian radiometer.

An aneroid barograph designed to record atmospheric pressure variations of very small magnitude.

The energy of any type of electromagnetic radiation. Also called radiation.

A unit of luminous flux. The lumen is equal to the luminous flux radiated into a unit solid angle (steradian) from a small source having a luminous intensity of one candle. An ideal source possessing an intensity of one candle in every direction would rad ...

check chamber-A chamber use to check the sensing elements of radiosonde equipment.

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

Federal Aviation Administration.

The difference between amounts of precipitation and runoff for a given storm. It is that portion of the precipitation that remains in the basin as soil moisture, surface storage, ground water, etc.