Same as atmometer.

The limiting values of ceiling, visibility, and wind, or runway visual range, established as safety minimum for aircraft landings and take-offs.

Abbreviation for precipitation effectiveness index.

See stage.

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.

The ratio of the output of an instrument to the input value, i.e. a rain gauge with a sensitivity of 1 tip per 0.01"

The measurement and computation of wind speeds and directions at various levels above the surface of the earth. Methods include pilot balloon observations, rabals, rawin or rawinsonde observations, radar tracking, or acoustic sounding.

A magnetometer of the electromagnetic type which is used to measure the horizontal intensity of the earth's magnetic field.

A direct-vision nephoscope constructed in the following manner: A grid-work of bars is mounted horizontally on the end of a vertical column and made free to rotate about the vertical axis. The observer rotates the grid and adjusts his or her position unti ...

Navy Operational Global Atmospheric Prediction System. A global meteorological model operated by the Department of Defense.

Defect in the action of an aneroid barometer resulting in a sluggish adjustment of the index toward the correct reading when the barometer is subjected to a large and rapid change in pressure.

A graphical representation of stage or discharge at a point on a stream as a function of time.

Particle on which the freezing of water occurs.

A large body of air having similar horizontal temperature and moisture characteristics.

The wind speed and direction at various levels in the atmosphere above the level reached by surface weather observations.

Same as instrument shelter.

A thermometer which utilizes the thermal properties of gas. There are two forms of this instrument: (a) a type in which the gas is kept at constant volume, and pressure is the thermometric property, and (b) a type in which the gas is kept at constant pres ...

The temperature at which a solid substance undergoes fusion, i.e. melts, changes from solid to liquid form. All substances have their characteristic melting points. For very pure substances the temperature range over which the process of fusion occurs is ...

Any one of numerous devices for the measurement of either speed alone or of both direction and speed (set and drift) in flowing water.

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.