Tables prepared from the psychrometric formula and used to obtain vapor pressure, relative humidity, and dew point from values of wet-bulb and dry-bulb temperatures.

The physical exposure of an instrument. The effect of immediate environment upon the representativeness of the measurements obtained by meteorological instruments is considerable and not always correctable. The purpose of the instrument shelter is to prov ...

An Instrument used to determine dew point.

Precipitation composed of balls or irregular lumps of ice with diameters between 5 and 50 mm.

The range through which the input may be varied without initiating a response. Usually expressed as a percentage of full-scale range.

A unit of mass numerically equal to the molecular weight of the substance. The gram-mote or gram-molecule is the mass in grams numerically equal to the molecular weight, i.e. a gram-mole of oxygen is 32 grams.

A small balloon whose ascent is followed by a theodolite in order to obtain data for the computation of winds aloft.

By international agreement, a period during which greatly increased observation of world-wide geophysical phenomena is undertaken through the co-operative effort of participating nations. July 1957-December 1958 was the first such year. However, precedent ...

The limiting values of ceiling, visibility, and wind, or runway visual range, established as safety minimum for aircraft landings and take-offs.

A thin metal disc partially evacuated of air used to measure atmospheric pressure by measuring its expansion and contraction.

An instrument for measuring the pressure of gases and vapors. A mercury barometer is a type of manometer.

A momentary decrease in the speed of the wind.

A type of climatic diagram whose coordinates are some form of temperature vs. a form of humidity or precipitation.

Same as parhelion.

The maximum difference in output for any given input (within the specified range) when the value is approached first with increasing, and then with decreasing, input signals. Caused by energy absorption in the elements of the measuring instrument. Usually ...

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

A device used to switch electrical current at a selectable setpoint temperature.

A type of atmometer. It is a pan used in the measurement of the evaporation of water into the atmosphere. The NWS Class A pan is a cylindrical container 48 inches in diameter and 10 inches deep.

A self-recording psychrometer.

A type of cistern barometer in which the level of mercury in the cistern is adjusted to the zero point of the scale before each reading.