An instrument for measuring snow hardness in terms of the resistance of snow to the pressure exerted by a disk attached to a spring-loaded rod, a gauge calibrated in pounds per square inch registers the amount of resistance. See Canadian hardness gauge.

The gravity flow of water within soil.

The array of indicating marks and figure in relation to which the position of an index is observed, i.e. a scale plate on a recorder.

Wind with a speed below 1 knot (1 mph); Beaufort scale number 0.

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

Precipitation of very small, white opaque particles of ice, fairly flat or elongated, with diameters less than 1 mm. The solid equivalent of drizzle.

The difference between amounts of precipitation and runoff for a given storm. It is that portion of the precipitation that remains in the basin as soil moisture, surface storage, ground water, etc.

The interval between the lower and upper measuring limits of an instrument, i.e. a thermometer with a range of -35 to 50

Forecasting weather by the use of numerical models, run on high speed computers. Most of the NWP for the National Weather Service is done at the National Centers for Environmental Prediction (NCEP).

A hygrometer which uses a transducing element whose electrical properties are a function of atmospheric water vapor content. The humidity strip and carbon-film hygrometer element are examples of such a transducer.

See calorie.

The ceiling classification which is applied when the ceiling height is determined by timing the ascent and disappearance of a ceiling balloon or pilot balloon.

The officially designated elevation of an airport above mean sea level, taken as the highest point on any of the runways of the airport. Same as airport elevation.

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

A remote indicator for wind speed and direction used in conjunction with a contact anemometer and a wind vane. The indicator consists of a center light, connected to the contact anemometer, surrounded by eight equally spaced lights which are individually ...

The temperature at which a solid substance undergoes fusion, i.e. melts, changes from solid to liquid form. All substances have their characteristic melting points. For very pure substances the temperature range over which the process of fusion occurs is ...

Any device or instrument for measuring salinity, especially one based on electrical conductivity methods.

See radiosonde commutator.

The transmission of data collected at a remote location over communications channels to a central station.

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