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.

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

The direction, with respect to magnetic north, from which the wind is blowing. Distinguish from true wind direction.

In general, the transformation of data from a "raw" form to some useable form. In meteorology, this often refers to the conversion of the observed value of an element to the value which it would theoretically have at some selected or standard level. The m ...

A colorless and odorless gaseous element. The lightest and apparently the most abundant chemical element in the universe. However, it is found only in trace quantities in the observable portion of our atmosphere, only about 0.00005 percent by volume of dr ...

An area of low barometric pressure, with its attendant system of winds. Also called a depression or cyclone.

A thermograph in which ventilation is provided by a suction fan.

The difference between the solar radiation directed downward and upward; net flux of solar radiation.

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

A numbering system using a base number of 2 and having only two digits: 0 and 1. The fundamental system of representing information with electrical pulses.

Ice crystal deposits formed by sublimation (conversion of water vapor directly to ice) when temperature and dew point are below freezing.

Video Display Terminal. An input and display device which includes a keyboard and a screen and allows a human to communicate with a computer.

That part of snow melt that reaches stream channels as runoff.

A wave disturbance in airflow due to some barrier in the flow. i.e. a hill or mountain.

Thermometer for measuring the temperature in the soil at different depths.

A vector term which includes both wind speed and wind direction.

A sunshine recorder of the type in which the time scale is supplied by the motion of the sun. It consists essentially of a spherical lens which bums an image of the sun upon a specialty prepared card.

meter-An instrument for measuring the transmissivity of the atmosphere; a type of transmissometer. It consists of a constant- intensity collimated light source located at a suitable distance from a photoelectric cell. Variation in the turbidity of the atm ...

A chronograph used to make a time-record of certain measured meteorological elements. The most common type, the triple register, records wind direction and speed, duration of sunshine, and amount of rainfall (sensed respectively by a contact anemometer, M ...

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 ...