A sudden, significant increase in station pressure.

A cone-tipped metal rod designed to be driven downward into deposited snow or firn. The measured amount of force required to drive the rod a given distance is an indication of the physical properties of the snow or firn.

A temperature scale with the ice point at 273 degrees and boiling point of water at 373 degrees. It is intended to approximate the Kelvin temperature scale with sufficient accuracy for many sciences, notably meteorology.

For a given locality and month, an empirical expression devised for the purpose of classifying climates numerically on the basis of precipitation and evaporation.

See ceilometer.

A hygrometer in which the sensitive element is a strand or strands of human hair, the length of which is a function of the relative humidity of the air.

A type of instrument shelter. It is a wooden box painted white with double louvered sides and mounted on a stand four feet above the ground.

A fabric cone attached to a metal ring and used to indicate wind direction. often at airfields.

A graphical aid used in fire weather forecasting to calculate the degree of forest-fire danger (or burning index). Commonly in the form of a circular slide rule, the firedanger meter relates numerical indices of (a) the seasonal stage of foliage, (b) the ...

Wind with a speed between 4 and 27 knots (4 and 31 mph); Beaufort scale numbers 2 through 6.

Instrument for measuring the depth of water from precipitation that is assumed to be distributed over a horizontal, impervious surface and not subject to evaporation.

A photoelectric spectrophotometer which is used in the determination of the ozone content of the atmosphere.

A method of upper air observation consisting of an evaluation of the wind speed and direction, temperature, pressure, and humidity aloft by means of a balloon-borne radiosonde tracked by radar or a radio theodolite.

Wind with a speed between 17 and 21 knots (19 and 24 mph); Beaufort scale number 5.

An instrument for measuring the intensity of direct solar radiation at normal incidence. See Angstrom compensation pyrheliometer, Eppley pyrheliometer, Michaelson actinograph. silver- disc pyrheliometer, spectropyrheliometer, waterflow pyrheliometer.

Difference between the temperatures of the dry-bulb and the wet-bulb thermometers of a psychrometer.

An aneroid barometer with a scale graduated in altitude instead of pressure units.

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 polariscope consisting of a specially constructed double plate polarizer and a tourmaline plate analyzer. Polarized light passing through the instrument is indicated by the presence of parallel colored fringes, while unpolarized light results in a unifo ...

A rain gauge or array of rain gauges designed to measure the inclination and direction of falling rain.