Name given to the unit of pressure in the International System of Units (SI). Equal to 1 newton/meter2 or 0.01 millibar.

The gravity flow of water within soil.

Pyrheliometer based on the comparison of the heating of two identical metal strips, one exposed to radiation, the other to a joule effect.

The unit of force in the centimeter-gram-second system of physical units, i.e. one gm cm per sec2, equal to 7.233 x 10-5 poundal.

The range of operating conditions within which a device is designed to operate and for which operating influences are stated. See operating conditions, reference operating conditions.

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

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

An estimate of the temperature of an incandescent body, determined by observing the wavelength at which it is emitting with peak intensity (its color) and using that wavelength in Wien's law.

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

An absolute temperature scale with the degree of the Fahrenheit scale and the zero point of the Kelvin scale. The freezing point of water equals 491.69

An instrument used for measuring geometric angles. See radio direction-finder.

A tube designed to measure the rate of flow of fluids. It consists of a tube having a constriction or throat at its midsection. The difference between the pressure measured at the inlet and at the throat is a function of the fluid velocity. Compare to Pit ...

Capacity of a soil or other surface to be penetrated by water sinking into the ground under the force of gravity. It thus expresses the rate of percolation.

An instrument for measuring temperature by utilizing the variation of the physical properties of substances according to their thermal states. Thermometers may be classified into types according to their construction; deformation thermometer, electrical t ...

Solar radiation scattered by particles in the atmosphere.

A flower-like diagram indicating the relative frequencies of different wind directions for a given station and period of time.

A wind blowing in a direction perpendicular to the course of a moving object.

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

An instrument for measuring differences of electric potential.

A curve showing the variation of temperature with height in the free air. See lapse rate.