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

Radiation coming from the solid angle of the sun's disc, as opposed to diffuse sky radiation, effective terrestrial radiation, or radiation from any other source. Direct solar radiation is measured by pyrheliometers.

In thermodynamics, the integrating factor of the differential equation referred to as the first law of thermodynamics, In statistical mechanics, a measure of translational molecular kinetic energy (with three degrees of freedom). In general, the degree of ...

A tube designed to measure the rate of flow of fluids. It consists of a tube having a constriction or throat at its midsection. The difference between the pressure measured at the inlet and at the throat is a function of the fluid velocity. Compare to Pit ...

Thermometer used for measuring the lowest temperature attained during a given interval of time, for example, a day.

A common type of terrestrial scintillation; shimmering over a hot surface (such as a roadway) on a quiet, cloudless. summer day.

The writing component of a recording instrument.

Any and all forms of water particles, liquid or solid, that fall from the atmosphere and reach the ground.

A sunshine recorder of the type in which the time scale is supplied by a chronograph. It consists of two bulbs, one of which is blackened, which communicate through a glass tube of small diameter. The tube is partially filled with mercury and contains two ...

The play or loose motion in an instrument due to the clearance existing between mechanically contacting parts.

That stage, on a fixed river gauge, at which overflow of the natural banks of the stream begins to cause damage in any portion of the reach for which the gauge is used as an index.

Same as marine rainbow.

Root Mean Square. This notation is used frequently with error analysis. In that context, it is the square root of the arithmetic mean of the squares of the deviations of the individual calibration points from the theoretical or ideal response.

An instrument for measuring the difference of the solar radiation falling on both sides of a horizontal surface from the whole hemisphere.

The time required for an instrument to register a designated percentage (frequently 90%) of a step change in the variable being measured.

A large plastic constant-level balloon for duration flying (in excess of 24 hours) at altitudes above 40,000 feet, used for the determination of wind fields and the measurement of upper atmospheric parameters.

Quantitative Precipitation Forecast.

The outer, solid portion of the earth: the crust of the earth.

See gust and peak gust.

Generally, a measure of the departure of the mean daily temperature from a given standard, one degree day for each degree (