A line of equal or constant pressure.

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

The nautical mile is closely related to the geographical mile which is defined as the length of one minute of arc on the earth's equator. By international agreement, the nautical mile is now defined as 1852 meters.

A generic term for any machine that enables a human being to communicate with a computer.

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 ...

A type of recording siphon barometer. The mechanically magnified motion of a float resting on the lower mercury surface is used to record atmospheric pressure on a rotating drum.

Of or pertaining to rain.

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

Balance of the water resources of a region, comparing precipitation and inflow with outflow, evaporation, and accumulation.

A device for measuring the height of tide. It may be simply a graduated staff in a sheltered location where visual observations can be made, or it may consist of an elaborate recording instrument (sometimes called a marigraph) making a continuous graphic ...

A unit of distance equal to 5280 feet. It is sometimes referred to as a land mile.

One of several constant-pressure levels in the atmosphere for which a complete evaluation of data derived from upper air observations is required.

An increase in the central pressure of a pressure system; opposite of a deepening. More commonly applied to a low rather than a high.

Particle on which the freezing of water occurs.

A large body of air having similar horizontal temperature and moisture characteristics.

An instrument which measures the rate of evapotranspiration. It consists of a vegetation soil tank so designed that all water added to the tank and all water left after evapotranspiration can be measured.

Any horizontal wind velocity tangent to the contour line of a constant pressure surface (or to the isobar of a geopotential surface) at the point in question.

The closeness of agreement among a number of consecutive output values measuring the same input value under the same operating conditions, approaching from the same direction. Usually measured as nonrepeatability but expressed as repeatability, a percenta ...

The portion of the strearnflow during any month or year derived from precipitation in previous months or years.

check chamber-A chamber use to check the sensing elements of radiosonde equipment.