A systematic summary of the terms (inflow, outflow, and storage) of the storage equation as applied to the computation of soil-moisture changes, ground-water changes, etc. An evaluation of the hydrologic balance of an area. Also called basin accounting, w ...

A momentary decrease in the speed of the wind.

A mercury barometer in which the tube is U-shaped and the upper and lower mercury surfaces have the same diameter.

A measure of the relative power, or of the relative values of two flux densities, especially of sound intensities and radar power densities. The decibel is derived from the less frequently used unit, the bel, named in honor of Alexander Graham Bell.

A clock-driven instrument mounting which automatically and continuously points in the direction of the sun. It is used with a pyrheliometera,hen continuous direct solar radiation measurements are required.

A device that allows a terminal or computer at one location to communicate with a terminal or computer at a distant location via wire or phone lines.

A mercury barometer which measures atmospheric pressure by weighing the mercury in the column or cistern.

A thermometer with a muslin-covered bulb which is moistened. used to measure wet-bulb temperature.

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.

An instrument which measures the transmissivity of the atmosphere between two points for the determination of visual range.

Electromagnetic radiation of shorter wavelength than visible radiation but longer than x-rays, between 0.02 and 0.4 micron (200 and 4000 angstrom).

A fixed support for mounting maximum and minimum thermometers of the liquid-in-glass type. The support holds the thermometers at the correct operating attitude and also permits their rotation for resetting when desired.

A type of electrical thermometer in which the thermal element is a substance whose electrical resistance varies with the temperature. Such thermometers can be made with very short time constants and are capable of highly accurate measurements.

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.

Rate of flow of water past a point in a stream, expressed as volume per unit time, i.e. cubic feet per second.

Eluding precise prediction, completely irregular.

Board that holds graph paper on which is plotted information obtained from a pilot-balloon observation.

See wind vane.

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

A balloon having a detachable tail which is released when the balloon has undergone a predetermined expansion. It thus serves to measure approximately the density of the atmosphere at the point of release.