A line drawn through points of equal humidity on given surface.

Determination of the total amount of snow covering a watershed or a given region. Both depth and water content of the snow may be measured, and the results may be used to predict the amount of water that will be available after melting.

Graduated fixed stake used in regions of abundant snowfall to facilitate the measurement of snow depth.

A unit of mass numerically equal to the molecular weight of the substance. The gram-mote or gram-molecule is the mass in grams numerically equal to the molecular weight, i.e. a gram-mole of oxygen is 32 grams.

A pressure tube anemometer, consisting of a pitot tube mounted on the windward end of a wind vane and a suitable manometer to measure the developed pressure and calibrated in units of wind.

Same as precipitation-evaporation ratio.

An instrument for taking photographs of an image of the sun in monochromatic light.

modulated radiosonde-A radiosonde which transmits the indications of the meteorological sensing elements in the form of pulses spaced in time. The meteorological data are evaluated from the intervals between the pulses. Also called timeinterval radiosonde ...

Same as geostrophic wind level.

See foehn.

Apparatus from which the nature and time of precipitation may be determined.

A unit of illuminance or illumination equal to one lumen per foot'. This is the illuminance provided by a light source of one candle at a distance of one foot.

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

An instrument for determining the degree of polarization of light. See photopolarimeter.

A reversing thermometer which is encased in a strong glass outer shell that protects it against hydrostatic pressure. Compare to unprotected thermometer.

The line-of-sight distance between two objects.

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.