A modification of the dew cell used in radiosonde equipment.

The ratios, to the mean wind speed, of the average magnitudes of the component fluctuations of the wind along three mutually perpendicular axes.

Negative Vorticity Advection.

The temperature at which an object gives out as much radiation as it receives from its surroundings.

A nephoscope in which the motion of the cloud is observed by its reflection in a mirror.

See sea-water thermometer, reversing thermometer.

February 2nd. In American folklore, a day that is popularly supposed to provide the key to the weather for the remainder of the winter. Specifically, if the ground-hog upon emerging from its hole casts a shadow, it will return underground, thereby forebod ...

An instrument which measures the transmissivity of the atmosphere between two points for the determination of visual range.

Hygrometer in which the dew (frost) point is determined by observing the temperature of an artificially cooled surface at the moment at which dew (frost) first appears on it.

A device for measuring the height of tide. It may be simply a graduated staff in a sheltered location where visual observations can be made, or it may consist of an elaborate recording instrument (sometimes called a marigraph) making a continuous graphic ...

The difference between the input quantity applied to a measuring instrument and the output quantity indicated by the instrument. The inaccuracy of an instrument is equal to the sum of its instrument error and its uncertainty.

A small pointer extending downward from the top of the cistern of a Fortin barometer. The level of the mercury in the cistern is adjusted so that it just comes in contact with the end of the pointer, thus setting the zero of the barometric scale.

Instrument which measures and records the amount of evaporation over time.

The average temperature of the air as indicated by a properly exposed thermometer for a given time period, usually a day, a month, or a year.

A device that combines several separate communications signals into one and outputs them on a single line.

Forecasting weather by the use of numerical models, run on high speed computers. Most of the NWP for the National Weather Service is done at the National Centers for Environmental Prediction (NCEP).

An instrument used to measure the water vapor content of the air.

In a system of moist air, the dimensionless ratio of the mass of water vapor to the total mass of the system.

The maximum rate at which precipitation can pass through the surface into the soil, for a given soil in a given condition.

The direction toward which the wind is blowing; with the wind.