The record of a barograph.

An inert gas. A colorless, monatomic element which is found to occur in dry air to the extent of only 0.000524 percent by volume. Helium is very light, having a molecular weight of only 4.003 and specific gravity referred to air of 0.138. Because helium i ...

Lowest altitude in the atmosphere over a given location at which the air temperature is 0

A pointed device which indicates the amount of resistance encountered when it is forced into a material such as snow or soil. See ram penetrometer.

The decrease of an atmospheric variable with height, the variable being temperature, unless otherwise specified.

Capacity of a soil or other surface to be penetrated by water sinking into the ground under the force of gravity. It thus expresses the rate of percolation.

Of equal or constant pressure, with respect to either space or time.

Upwarddirected solar radiation, reflected by the earth's surface and the atmosphere.

The process whereby a position on the scale of an instrument is identified with the magnitude of the signal (or input force) actuating the instrument.

A psychrometer in which the ventilation is provided by a suction fan.

An instrument that shows changes in humidity.

Name sometimes given to a transmissometer.

The upward force produced by the gas in a balloon. It is equal to the free lift plus the weight of the balloon and the attached equipment.

A relatively small-scale, downward moving current of air.

A device for measuring sea-surface waves. It consists of a weighted pole below which a disk is suspended at a depth sufficiently deep for the wave motion associated with deepwater waves to be negligible. The pole will then remain nearly as if anchored to ...

The total amount of water transferred to the atmosphere by evapotranspiration.

Thermometer for measuring the temperature in the soil at different depths.

A measure, proposed by Angstrom, of the precipitation effectiveness of a region.

Frozen or partly frozen rain.

The difference between temperature measurements taken at two significant levels above the ground. Temperatures at 10 and 40 meters are commonly used.