Forecasting weather by the use of numerical models, run on high speed computers. Most of the NWP for the National Weather Service is done at the National Centers for Environmental Prediction (NCEP).

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 colorless and odorless gaseous element. The lightest and apparently the most abundant chemical element in the universe. However, it is found only in trace quantities in the observable portion of our atmosphere, only about 0.00005 percent by volume of dr ...

Same as aneroid barometer. Holostelic means wholly made of solids, while aneroid means devoid of liquid.

The indicating part of an instrument. For example, the hand of a watch or the meniscus of a mercury column.

Abbreviation for the pressure, temperature, and humidity data obtained by a radiosonde observation.

See ceilometer.

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

A thermometer designed for use in measuring the temperature of sea water. One form consists of a mercury-in-glass thermometer protected by a perforated metal case. Another form consists of a mercury-in-glass thermometer surrounded by a metal case which fo ...

For a given location, a measure of the long-range effectiveness of precipitation in promoting plant growth. Also called precipitation-evaporation index.

Rate of wind movement in distance per unit time.

A record obtained from a meteorograph. A chart in which meteorological variables are plotted against time.

Air in motion relative to the surface of the earth. Almost exclusively used to denote the horizontal component.

Companion to the wet-bulb thermometer in a psychrometer. Used to measure ambient air temperature.

Wind with a speed between 28 and 55 knots (32 and 63 mph); Beaufort scale numbers 7 through 10.

The ratio of the amount of electromagnetic radiation reflected by a body to the amount incipient upon it, commonly expressed as a percentage. The albedo is to be distinguished from the reflectivity, which refers to one specific wavelength.

See river basin.

An empirical curve relating stream discharge or stage at a point on a stream to discharge or stage at one or more upstream points and, possibly. to other parameters. Also called stage relation.

The record of a barograph.

A recording hair hygrometer.