A momentary decrease in the speed of the wind.

An early and once universal name for the mercury barometer.

The temperature to which a sample of air must be cooled, while the mixing ratio and barometric pressure remain constant, in order to attain saturation by water vapor. When this temperature is below O

A type of pressure-tube anemometer, named after the inventor.

A measure of the degree to which the weather or climate of a region is favorable to the process of evaporation. Usually considered to be the rate of evaporation. under existing atmospheric conditions, from a surface of water which is chemically pure and h ...

Water vapor content of the air. See absolute humidity, dew point, mixing ratio, relative humidity, specific humidity.

Anemometer which measures wind speed by measuring the degree of cooling of a metal film heated by an electric current. A type of cooling-power anemometer.

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.

Technically, the temperature registered by the dry-bulb thermometer of a psychrometer. However, it is identical with the temperature of the air and may also be used in that sense.

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

Any emission of light at temperatures below that required for incandescence.

Similar to the spectroheliograph, but used for visual instead of photographic purposes.

The combined processes by which water is transferred from the earth's surface to the atmosphere: evaporation of liquid or solid water plus transpiration from plants.

In a system of moist air, the dimensionless ratio of the mass of water vapor to the mass of dry air. For many purposes, the mixing ratio may be approximated by the specific humidity.

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

Instrument which measures and records the amount of evaporation over time.

check chamber-A chamber use to check the sensing elements of radiosonde equipment.

The change in barometric pressure within a specified period of time (typically 3 hours for meteorological observations).

Ice crystal deposits formed by sublimation (conversion of water vapor directly to ice) when temperature and dew point are below freezing.

bucket rain gauge-A rain gauge where the precipitation collected by the receiver empties into one side of a chamber which is partioned transversely at its center and is balanced bistably upon a horizontal axis. When a predetermined amount of water has bee ...