A line of equal or constant temperature.

A thermopile used in some types of radiation instruments. See solarimeter.

An elongated area of relatively low atmospheric pressure. Usually associated with and most clearly identified as an area of maximum cyclonic curvature of the wind flow. The opposite of a ridge.

A measure of long-term precipitation effectiveness. The ratio of the normal annual rainfall to the normal annual evaporation.

An effect noted primarily in wet snow conditions when snow clings to the sides of a precipitation gauge and gradually accumulates until the gauge orifice is capped with accumulated snow. This effect can be minimized by using large collectors, and wind scr ...

The mean difference between the readings of a given instrument and those of a standard instrument.

Same as parhelion.

The atmospheric pressure computed using station elevation as the reference datum level. Station pressure is usually the base value from which sea level pressure and altimeter setting are determined.

Any and all forms of water particles, liquid or solid, that fall from the atmosphere and reach the ground.

The lowest value of a measured quality at which a sensor meets its accuracy specification.

The actual lifting force of an inflated balloon, usually expressed in grams.

In general. the severe wind of an intense tropical cyclone (hurricane or typhoon). The term has no further technical connotation, but, unfortunately, is easily conftlsed with the strictly defined hurricane-force wind,

A graphical representation of stage or discharge at a point on a stream as a function of time.

A photometer which measures the intensity of radiation as a function of the frequency (or wavelength) of the radiation.

That stage, on a fixed river gauge, at which overflow of the natural banks of the stream begins to cause damage in any portion of the reach for which the gauge is used as an index.

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.

The study of waters (including oceans, lakes, and rivers) embracing either: (a) their physical characteristics, from the standpoint of the oceanographer or limnologist; or (b) the elements affecting safe navigation, from the point of view of the mariner. ...

A thermometer, invented by James Six in 1782, which simultaneously indicates the maximum and minimum temperatures attained during a given interval of time. A U-tube min/max thermometer

A magnetometer of the electromagnetic type which is used to measure the horizontal intensity of the earth's magnetic field.

Very small precipitation drops (diameters less than 0.5 mm) that appear to float with air currents while falling in an irregular path. Unlike fog droplets, drizzle falls to the ground.