A recording anemometer.

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

Any twelve-month period, usually selected to begin and end during a relative dry season. Used a basis for processing streamflow and other hydrologic data. The period from October 1 to September 30 is widely used in the U.S.

A pointed device which indicates the amount of resistance encountered when it is forced into a material such as snow or soil. See ram penetrometer.

A balloon used to carry a radiosonde aloft, considerably larger than pilot balloons or ceiling balloons.

That temperature at which, in a specified latitude, the reading of a particular barometer requires no temperature or latitude correction.

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

A barometer which measures atmospheric pressure using one or a series of aneroid capsules. Also called holosteric barometer.

Phase Shift Keying. A form of phase modulation of a data signal performed by a modem for transmission over dedicated wire or phone lines.

Lowest altitude in the atmosphere over a given location at which the air temperature is 0

pattern barometer-Mercurial barometer with a fixed scale and cistern and which therefore requires only one adjustment before each reading.

A wind blowing in a direction opposite to the heading of a moving object, thus opposing the object's intended progress; the opposite of a tailwind.

Situated on the side from which the wind blows.

modulated radiosonde-A radiosonde which transmits the indications of the meteorological sensing elements in the form of pulses spaced in time. The meteorological data are evaluated from the intervals between the pulses. Also called timeinterval radiosonde ...

A number of quantity defining a limit that errors will not exceed when a device is used under specified operating conditions. Accuracy rating can be expressed in a number of forms, i.e. in terms of the measured variable (+/- 1 C), percent of span (+/-0.5% ...

The condition of the atmosphere when the amount of water vapor present is the maximum possible at the existing temperature.

An instrument for measuring differences in electric potential.

Same as parhelion.

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

An instrument for recording global solar radiation.