A generic term for any machine that enables a human being to communicate with a computer.

A photometric unit of illuminance or illumination equal to one lumen per square centimeter.

The ratios, to the mean wind speed, of the average magnitudes of the component fluctuations of the wind along three mutually perpendicular axes.

A sudden brief increase in the speed of the wind, followed by a lull or slackening. Compare to peak gust.

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 ...

Any source of radiant energy, especially electromagnetic energy.

The difference between downward and upward (total) radiation; net flux of all radiation.

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

The average temperature of the air as indicated by a properly exposed thermometer for a given time period, usually a day, a month, or a year.

The record made by a hygrograph.

An instrument designed to measure the effect of sunlight on evaporation from plant foliage. It consists of a porous clay atmometer whose surface has been blackened so that it absorbs radiant energy.

Water condensed onto objects at or near the ground, due to the fact that their temperatures have fallen below the dew point temperature of the surrounding air, but not below freezing.

The intensity (flux per unit solid angle) of visible radiation weighted to take into account the variable response of the human eye as a function of the wavelength of light. Usually expressed in candles.

A pyrheliometer of the thermoelectric type. Radiation is allowed to fall on two concentric silver rings, the outer covered with magnesium oxide and the inner covered with lamp black. A system of thermocouples (thermopile) is used to measure the temperatur ...

Forecasting weather by the use of numerical models, run on high speed computers. Most of the NWP for the National Weather Service is done at the National Centers for Environmental Prediction (NCEP).

Same as river gauge.

February 2nd. In American folklore, a day that is popularly supposed to provide the key to the weather for the remainder of the winter. Specifically, if the ground-hog upon emerging from its hole casts a shadow, it will return underground, thereby forebod ...

A component of a radiosonde consisting of a series of alternate electrically conducting and insulating strips. As these are scanned by a contact the radiosonde transmits temperature and humidity signals alternately. The contact may be a baroswitch as in t ...

See sea-water thermometer, reversing thermometer.

A device which surrounds a rain gauge and acts to maintain horizontal flow in the vicinity of the funnel so that the catch will not be influenced by eddies generated near the gauge. See Alter shield, Nipher shield, Wild fence.