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

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.)

Same as recording rain gauge.

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

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

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

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

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

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

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.

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

Same as rain gauge.

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

A recording siphon barometer.

Contraction for pilot balloon observation.

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

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.

Apparatus designed to measure the amount of precipitation falling in the form of snow. The device determines the weight of the snow or the volume of water after the snow melts.