The record made by a hygrograph.

February 2nd. In American folklore, a day that is popularly supposed to provide the key to the weather for the remainder of the winter. Specifically, if the ground-hog upon emerging from its hole casts a shadow, it will return underground, thereby forebod ...

In meteorology, a deflecting force acting on a body in motion and resulting from the earth's rotation. It deflects air currents to the right in the northern hemisphere and to the left in the southern hemisphere, thus having an effect on wind direction.

An instrument which indicates the presence of dust particles in the atmosphere. Also spelled coniscope.

A device used on certain types of instruments to prevent unwanted radiation from affecting the measurement of a quantity. Also called solar radiation shield.

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

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

The elevation of the water surface in a stream as measured by a river gauge with reference to some arbitrarily selected zero datum.

Quantitative Precipitation Forecast.

Same as precipitation-evaporation ratio.

See hurricane beacon.

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

A line drawn through all points on a map having the same amount of cloudiness.

The inherent imprecision of a given process of measurement, the unpredictable component of repeated independent measurements of the same object under sensibly uniform conditions.

The total infrared radiation emitted from the earth's surface. To be carefully distinguished from atmospheric radiation, effective terrestrial radiation, and insolation.

Name given to the unit of pressure in the International System of Units (SI). Equal to 1 newton/meter2 or 0.01 millibar.

An instrument consisting of a series of graduated cylinders possessing selective collection efficiencies. It is used for the measurement of quantities relating to the size distribution of cloud droplets.

An instrument which measures evaporation by measuring the loss of water from a burette reservoir through a ceramic disc.

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.

The amount of precipitation captured by a rain gauge.