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 line of equal or constant pressure.

An instrument which measures combined direct solar radiation and diffuse sky radiation. See pyrheliometer, Robitzsch actinograph. solarimeter. See also albedometer.

An instrument, located at the surface observing station, which is used to record the data presented by a radiosonde aloft.

A photometer which measures the intensity of radiation as a function of the frequency (or wavelength) of the radiation.

A type of pressure-plate anemometer in which the plate, restrained by a stiff spring, is held perpendicular to the wind. The wind-activated motion of the plate is measured electrically. The natural frequency of this system can be made high enough so that ...

Hygrometer in which the dew (frost) point is determined by observing the temperature of an artificially cooled surface at the moment at which dew (frost) first appears on it.

A rotation anemometer which has a horizontal axis upon which helicoidal shaped vanes are mounted. See windmill anemometer.

Very generally, any moving- stream of air. It has no particular technical connotation.

An instrument which automatically records the voltage applied to it, as a function of time.

Wind with a speed between 7 and 10 knots (8 and 12 mph), Beaufort scale number 3.

A halo consisting of a faint white circle passing through the Sun and running parallel to the horizon for as much as 360

An elongated area of relatively high pressure. Usually associated with and most clearly identified as an area of maximum anticyclonic curvature of the wind flow. The opposite of a trough.

A measure of the intrinsic luminous intensity emitted by a source in a given direction. Luminance is a measure only of light. The comparable term for electromagnetic radiation in general is radiance.

Value of soil moisture, expressed as a percentage of the mass of dry soil, below which a plant living in the soil dies by wilting.

Winds which, over a small area, differ from those which would be appropriate to the general pressure distribution.

Quantitative Precipitation Forecast.

A mercury barometer in which the lower mercury surface is larger in area than the upper surface. The basic construction of a cistern barometer is as follows: A glass tube one meter in length, sealed at one end is filled with mercury, and then inverted. Th ...

A unit of illuminance or illumination equal to one lumen per foot'. This is the illuminance provided by a light source of one candle at a distance of one foot.

The lowest level at which the wind becomes geostrophic in the theory of the Ekman spiral. Also called gradient wind level.