Solar and terrestrial radiation directed downwards (towards the earth's surface); incoming radiation.

The time required for an instrument to register a designated percentage (frequently 90%) of a step change in the variable being measured.

The cardinal points of the compass, i.e. north, south, east, west.

An instrument used to measure changes in the level of the water in an evaporation pan. The gauge is normally placed in a Stillwell and adjusted so that the point of the hook just breaks the water surface. The change in water level is read on the attached ...

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

Precipitation falling from a cloud, usually in wisps or streaks, but evaporating before it reaches the ground.

The correction applied to an instrument to account for the effect of temperature upon its response characteristics.

A unit that represents one degree of deviation from a reference point in the mean daily outdoor temperature (usually 65

Particle on which the freezing of water occurs.

The succession of stages through which water passes on the ground and in the atmosphere: evaporation from land or bodies of water, condensation to form clouds, precipitation, accumulation in the soil or in bodies of water, and re-evaporation.

A type of cooling-power anemometer based upon the principle that the time constant of a thermometer is a function of its ventilation.

Of equal or constant pressure, with respect to either space or time.

Wind with a speed between 22 and 27 knots (25 and 31 mph); Beaufort scale number 6.

Difference between the instantaneous wind velocity at a point and the mean wind velocity taken over a given time interval. Also called fluctuation velocity.

An absolute temperature scale with the ice point of pure water defined as 273.16 K. The size of the degree is the same as on the Celsius scale, and the zero point is absolute zero.

Winds from the four cardinal points of the compass; that is, north, east, south, and west winds.

The upward force produced by the gas in a balloon. It is equal to the free lift plus the weight of the balloon and the attached equipment.

A type of wind vane having a split or V-shaped tail. The apex orients itself to the direction of the wind.

Pertaining to rain, or more broadly, to precipitation.

A thermometer. the sensitive element of which consists of two metal strips which have different coefficients of expansion and are brazed together. The distortions of the system in response to temperature variations are used as a measure of temperature. It ...