- Industry: Weather
- Number of terms: 60695
- Number of blossaries: 0
- Company Profile:
The American Meteorological Society promotes the development and dissemination of information and education on the atmospheric and related oceanic and hydrologic sciences and the advancement of their professional applications. Founded in 1919, AMS has a membership of more than 14,000 professionals, ...
An instrument for determining the degree of polarization of light. See photopolarimeter.
Industry:Weather
An instrument used to measure humidity. It consists of two thermometers exposed side by side, one of which (the dry bulb) is an ordinary glass thermometer, while the other (the wet bulb) has its bulb covered with a jacket of clean muslin that is saturated with distilled water prior to an observation. The temperature measured by the wet-bulb thermometer is generally lower (due to evaporation of water from the wet bulb) than that measured by the dry bulb. The difference in the temperatures is a measure of the humidity of the air; the lower the ambient humidity, the greater the rate of evaporation and, consequently, the greater the depression of the wet-bulb temperature. The size of the wet-bulb depression is related to the ambient humidity by the psychrometric formula. See aspiration psychrometer, Assmann psychrometer, sling psychrometer.
Industry:Weather
An instrument used to measure and record earthquake vibrations and other earth tremors. It consists essentially of a heavy pendulum hung so that it can swing freely in one direction. A pen is attached to the end of the pendulum so that the pendulum's motion, relative to a recorder fixed solidly to the earth, may be determined. A seismological observatory requires three seismographs in order to measure the three component directions of the tremors and to fix approximately their origin. A study of the records of sensitive seismographs has shown that some of the tremors may be attributed to oceanographic and atmospheric phenomena. See microseism.
Industry:Weather
An instrument for measuring the index of refraction of a liquid, gas, or solid. Refractometers in general use in meteorology operate in the microwave region and are based on the principle that the resonant frequency of a cavity depends on the dielectric constant of its contents. In the Crain refractometer, a microwave oscillator is stabilized by the cavity at its resonant frequency. Two such stabilized systems are used, one with a sealed cavity and one with a perforated cavity open to the atmosphere. These are spaced in frequency by 30–50 MHz, and the difference frequencies are measured. The change in difference frequency is almost linearly related to the change in refractive index of the perforated cavity's contents. The Birnbaum refractometer is similar in its operating principles.
Industry:Weather
An instrument used to determine approximately the amount of cloudiness during the dark hours. It consists of a fixed long-focus camera positioned so that Polaris is permanently within its field of view. The apparent motion of the star appears as a circular arc on the photograph and is interrupted as clouds come between the star and the camera.
Industry:Weather
An instrument consisting of a series of graduated cylinders possessing selective collection efficiencies. It is used for the measurement of quantities relating to the size distribution of cloud droplets. See impactor.
Industry:Weather
An instrument used to detect the presence of and to determine the information carried by electromagnetic radiation. A receiver includes circuits designed to detect, amplify, rectify, and shape the incoming radio- frequency signals received at the antenna in such a manner that the information-containing component of this received energy can be delivered to the desired indicating or recording equipment.
Industry:Weather
An instrument that automatically records the amount of precipitation collected as a function of time. The most common types, according to their principle of operation, are 1) tipping-bucket rain gauge, 2) weighing rain gauge, 3) capacitance rain gauge, and 4) optical rain gauge.
Industry:Weather
An instrument used for the measurement of direct solar radiation. It consists of a silver disk located at the lower end of a tube containing a diaphragm that serves as the radiation receiver for a calorimeter. Radiation falling on the silver disk is periodically intercepted by means of a shutter located in the tube, causing temperature fluctuations of the calorimeter that are proportional to the intensity of the radiation. The instrument is normally used as a secondary instrument and is calibrated against the water-flow pyrheliometer. It was used by the U. S. Weather Bureau as a standard instrument. Currently, this instrument's function has been replaced by an absolute cavity radiometer. See pyrheliometer, cavity radiometer.
Industry:Weather
An inorganic chemical compound, AgI, that has a crystalline structure (symmetry; lattice spacing) similar to ice and a very low solubility in water, and can be easily generated as an aerosol. It was discovered by Bernard Vonnegut in 1947 after a search of the crystallographic tables as an effective nucleating agent for supercooled water. In cloud seeding applications it is usually combined with small amounts of other materials (e.g., bromine, chlorine, copper) to enhance nucleating properties through change of lattice dimension to approach more closely that of ice.
Industry:Weather
