The succession of stages through which water passes on the ground and in the atmosphere: evaporation from land or bodies of water, condensation to form clouds, precipitation, accumulation in the soil or in bodies of water, and re-evaporation.

A graphical representation of a frequency distribution. The range of the variable is divided into class intervals for which the frequency of occurrence is represented by a rectangular column. The height of the column is proportional to the frequency of ob ...

A wind (or component thereof) directed down the slope of an incline and caused by greater air density near the slope than at the same levels some distance horizontally from the slope. Also called drainage wind and sometimes called katabatic wind.

A modification of the dew cell used in radiosonde equipment.

A nephoscope in which the motion of the cloud is observed by its reflection in a mirror.

The direction, with respect to true north, from which the wind is blowing. Distinguish from magnetic wind direction. In all standard upper-air and surface weather observations, it is true wind direction that is reported.

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.

See hook gauge.

The maximum rate at which precipitation can pass through the surface into the soil, for a given soil in a given condition.

Movernent of water through the soil surface into the soil, or the quantity of water entering the soil. Infiltration is equal to the total precipitation less the losses due to interception by vegetation. retention in depressions on the land surface, evapor ...

Frequency Shift Keying. A form of frequency modulation of a data signal performed by a modem for transmission over dedicated wire or phone lines.

A box-like structure designed to protect certain meteorological instruments from exposure to direct sunlight, precipitation, and condensation, while at the same time providing adequate ventilation. Instrument shelters are painted white, have louvered side ...

The flux of visible radiation, so weighted as to account for the manner in which the response of the human eye varies with the Wavelength of radiation. The basic unit for luminous flux is the lumen,

Similar to the spectroheliograph, but used for visual instead of photographic purposes.

Instrument which measures and records the amount of evaporation over time.

Pertaining to measurements or devices in which the output vanes in discrete steps, i.e. on-off or pulse signals. Compare to analog.

The sum of solar and terrestrial radiation.

An instrument which measures the instantaneous rate at which rain is falling on a given surface. Also called a rate-of-rainfall gauge.

The ratio of the actual amount of water evaporated into the atmosphere to the evaporative power. Also called relative evaporation.

A cylinder installed in a body of water or an evaporation pan to hold a sensor, such as a float to measure water level or a hook gage. The stillwell is constructed so that there is free movement of water in and out of it, and it therefore provides a repre ...