A method of winds aloft observation essentially the same as a pilot balloon observation except the height data is derived from the radiosonde observation rather than from assumed ascension rates.

The atmospheric pressure at the level of the barometer. May or may not be the same as station pressure.

The height ascribed to the lowest layer of clouds or obscuring phenomena when it is reported as broken, overcast, or obscuration and not classified as "thin" or "partial." The ceiling is termed unlimited when these conditions are not satisfied. ...

Same as precipitation- effectiveness index.

A form of psychrometer with wet-bulb and dry-bulb thermometers mounted on opposite sides of a specialty designed graph of the psychrometric tables. It is so arranged that the intersections of two curves determined by the wet-bulb and dry-bulb readings -yi ...

Determined by weighing a special type of wooden stick that has been exposed in the woods, its weight being proportional to its contained water.

A computed characteristic of a particular river basin, expressed as the time difference between the time-center of mass of rainfall and the time-center of mass of resulting runoff.

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

The state of the weather with respect to its effect upon the kindling and spreading of forest fires.

A constant which describes the performance of a wind vane in response to a step change in wind direction. It is calculated from the relative amount of overshoot on two successive swings (half cycles) of a decaying oscillation. This specification is dimens ...

See standard atmosphere.

One of the radiation laws which states that the wavelength of maximum radiation intensity for a black body is inversely proportional to the absolute temperature of the radiating black body.

Abbreviation for visual flight rules, but commonly used to refer to the relatively favorable weather and/or flight conditions to which these rules apply.

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

A subtle, diumal component of the wind velocity leading to a diumal shift of the wind or turning of the wind with the sun, produced bv the east-to-west progression of daytime surface heating.

A recording weight barometer.

Thermometer used for measuring the highest temperature attained during a given interval of time, for example, a day.

Precipitation composed of white or translucent ice crystals, chiefly in complex branched hexagonal forms.

A wind blowing in the same direction as the heading of a moving object. thus assisting the object's intended progress. The opposite of a head wind.

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