- 업종: Weather
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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, ...
With this optical technique, one measures the difference in light absorption of the species of interest between a maximum and minimum in the spectrum. The technique most often uses the visible or ultraviolet regions of the spectrum. A broadband continuous white light source, generally a high-pressure Xe lamp or incandescent quartz-iodine lamp, is used for this purpose, but light from the sun and the moon have also been used. Differential optical absorption has been used in the atmosphere to detect gas molecules such as ozone, sulfur dioxide, nitrogen dioxide, nitrate radical (NO3), and hydroxyl radical (OH), with sensitivities ranging from the low parts-per-trillion (ppt) level to several hundred ppt.
Industry:Weather
A device used to remove from a flowing gas stream a predictable fraction of particles within a narrow size range based upon electrical mobility. The electrical mobility is defined as the electrical velocity of the particle divided by the field strength. This device consists of two cylindrical electrodes, an outer ground electrode and an inner rod to which a precise negative voltage is applied. The sample flow is introduced into an annular gap between the two electrodes and flows through the device along with an inner core of particle- free sheath air without mixing. Particles with positive charges are attracted through the sheath air toward the negatively charged center electrode. Only those particles within a narrow mobility range pass through a slit near the bottom of the center electrode.
Industry:Weather
Method of determining from the pressure and wind fields, using kinematic equations, certain parameters relating to the movement and development of synoptic features.
Industry:Weather
The hypothetical area normal to the incident radiation that would geometrically intercept the total amount of radiation actually backscattered per unit solid angle (i.e., through a scattering angle of 180°) by a particle.
Industry:Weather
General term for a chart showing the amount and direction of change of a meteorological quantity in time or in space, for example, change chart, vertical differential chart. See differential analysis.
Industry:Weather
In bomb ballistics, the wind vector that is the weighted average of all the differential winds from the bomb-release altitude down to the target. The differential ballistic wind is the basis for calculation of the Q-factor in the bomb-sight setting.
Industry:Weather
The difference in the loss of power, due to propagation, experienced by two signals that differ in one attribute, for example, polarization or wavelength. As applied to polarimetric radar observations, the differential attenuation is defined relative to the axes of the propagation medium for which the attenuation is minimum and maximum. These axes are described as the principal axes of the medium.
Industry:Weather
Synoptic analysis of change charts or of vertical differential charts (such as thickness charts) obtained by the graphical or numerical subtraction of the patterns of some meteorological variable at two times or two levels. Spatial differential analysis from one surface to another in the vertical is useful because of its relation to hydrostatics: Differential analysis of pressure at low levels gives the mean isopycnic lines for the layer; differential analysis of temperature and potential temperature at two levels approximates the mean stability for the layer; and differential analysis of the topographies of two different isobaric surfaces gives the pattern of thickness or mean virtual isotherms for the layer.
Industry:Weather
(Abbreviated DIAL thermometer. ) An active remote sensor that measures temperature using a laser. To measure temperature, a DIAL thermometer transmits three wavelengths: one on an oxygen absorption band, one off the band, and one at the transition wavelength in between. With this technique, the concentrations of oxygen in various energy states can be measured. Many of the high rotational energy states of oxygen are temperature dependent, allowing temperature to be inferred from the DIAL measurements. This method requires very high accuracy, spectral resolution, and stability of the laser transmitter and detector, which are characteristics that are almost achieved at present.
Industry:Weather
A specification of the angular distribution of the electromagnetic energy scattered by a particle or a scattering medium. The differential (scattering) cross section is defined as the ratio of the intensity of radiant energy scattered in a given direction to the incident irradiance and thus has dimensions of area per unit solid angle. The symbol σ is frequently used for scattering cross section and dσ/dΩ for the differential cross section.
Industry:Weather
