Generally, the relative states of inflow, outflow, and storage of moisture over a given area of earth's surface.

A current meter consisting of six conical cups, mounted around a vertical axis, which rotate and generate a signal with each rotation. Tail vanes and a heavy weight stabilize the instrument.

A small balloon whose ascent is followed by a theodolite in order to obtain data for the computation of winds aloft.

Line drawn through geographical points recording equal amounts of precipitation during a given time period or for a particular storm.

Radiation with wavelengths greater than 4 microns. (In meteorology, same as infrared radiation.)

A scale of yellows, greens, and blues for recording the color of sea water, as seen against the white background of a Secchi disk.

A line drawn through geographical points where a given seasonal biological event occurs on the same date.

Wind with a speed between 11 and 16 knots (13 and 18 mph); Beaufort scale number 4.

Diffuse solar radiation which has the same intensity in all directions.

An element that can control current without moving parts, heated filaments, or vacuum gaps.

Moisture contained in the soil above the water table, including water vapor which is present in the soil pores. In some cases this term refers strictly to the humidity contained in the root zone of plants.

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

A set of rules or conventions used to standardize data transfer between devices.

Same as rain gauge.

Snow shower, particularly of a very light and brief nature.

The processing of the form or mode of a signal so as to make it intelligible to, or compatible with, a given device.

A recording siphon barometer.

Contraction for pilot balloon observation.

Atmospheric layer throughout which there is no change of temperature with height, i.e. a zero lapse rate.

The amount of precipitation falling in one day, or other specified period, that is likely to be equalled or exceeded in any given place only once in a century. That is, a precipitation amount that has a return period of 100 years.