Same as dew-point hygrometer.

A thermodynamic change of state in a system in which there is no transfer of heat or mass across the boundaries of the system. In an adiabatic process, compression always results in warming, expansion in cooling. Compare to diabatic process.

Moisture contained in the soil above the water table, including water vapor which is present in the soil pores. In some cases this term refers strictly to the humidity contained in the root zone of plants.

An atmospheric phenomenon, other than clouds, which obscures a portion of the sky from the point of observation. Also called obscuration.

That temperature at which, in a specified latitude, the reading of a particular barometer requires no temperature or latitude correction.

Automated Local Evaluation in Real Time. Network of automatic rain gauges that transmit via VHF radio link when precipitation occurs. Some sites are also equipped with other sensors such as temperature, wind, pressure, river stage or tide level. More info ...

A line drawn through geographical points having the same pluvial index.

An instrument used to measure the amount of dew formed on a given surface.

That horizontal wind velocity at which the Coriolis acceleration exactly balances the horizontal pressure force. It is directed along contour lines or isobars.

Negative Vorticity Advection.

A hydrometeor consisting of an aggregate of microscopic and more-or-less hygroscopic water droplets suspended in the atmosphere. It reduces visibility to a lesser extent than fog. The relative humidity of mist is often less than 95 percent.

For a given location, a measure of the long-range effectiveness of precipitation in promoting plant growth. Also called precipitation-evaporation index.

The record of an aneroid barograph.

Snow gauge composed of a metal cylinder, closed at one end, used to obtain a sample of snow from which the water is measured after melting.

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 ...

The actual time during which physical events take place.

A river gauge in which a weight suspended on a wire is lowered to the water surface from a bridge or other overhead structure to measure the distance from a point of known elevation to the water surface.

The volume of liquid water evaporated per unit area in unit time. usually measured as the depth of liquid water lost per unit time from the whole area.

A definite portion of a stream channel, commonly taken between two gauging stations, but may be taken between any two specified points.

See feed.