- 行业: 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, ...
Roll circulations approximately aligned with the surface stress vector that frequently occur in the upper boundary layer of oceans or lakes. Although similar in form to atmospheric longitudinal roll vortices, Langmuir circulations are thought to be driven by nonlinear interactions between the surface gravity wave field and the larger-scale turbulent motions within the mixed layer. They are sometimes called windrows because they form lines of surface debris or bubbles in their surface convergence zones. Their spatial scale is related to the depth of the mixed layer and their characteristic velocity is on the order of 8u*, where u* is the friction velocity in water. As a result of this scaling, Langmuir circulations generally require surface winds of at least 8 m s−1 in order to form. See coherent structures, longitudinal rolls.
Industry:Weather
Relatively strong winds concentrated within a narrow stream in the atmosphere. While this term may be applied to any such stream regardless of direction (including vertical), it is coming more and more to mean only a quasi-horizontal jet stream of maximum winds embedded in the midlatitude westerlies, and concentrated in the high troposphere. The question of the maintenance of the jet stream is a cardinal problem of theoretical meteorology. Two such jet streams are sometimes distinguished. The predominant one, the polar-front jet stream, is associated with the polar front of middle and upper-middle latitudes. Very loosely, it may be said to extend around the hemisphere, but, like the polar front, it is discontinuous and varies greatly from day to day. A subtropical jet stream is found, at some longitudes, between 20° and 30° latitude and is strongest off the Asian coast. Currently, in the analysis of upper-level charts, a jet stream is indicated wherever it is reliably determined that the wind speed equals or exceeds 50 knots. See thermal jet.
Industry:Weather
Region of convergence, often a line, downwind of a mountain or mountain ridge during fair-weather daytime conditions that are favorable for the formation of thermally forced upslope flow and deep convective mixing. Convergence forms between upslope (or sometimes light and variable) flow at lower elevations of the lee slopes and downslope flow at higher elevations, which results from the downward convective mixing of ambient momentum from the flow above ridgetops. With moist upslope flow and favorable conditions, updrafts produced by the convergence can lead to mountain cumulus formation, or trigger thunderstorm or severe weather activity.
Industry:Weather
Ratio of mean free path of air molecules to particle radius; a measure of its ability to behave as a molecule or a particle.
Industry:Weather
Procedures to prevent the occurrence of lightning. Seeding below cloud base with 10-cm fiber chaff in a Colorado study resulted in corona discharges that caused a discharging current to flow within developing or active thunderstorms. Electric fields below thunderstorms seeded with chaff decayed much faster than electric fields below nonseeded storms, and chaff seeding of existing thunderstorms greatly reduced cloud-to-ground flashes compared to nonseeded storms. Recent evidence suggests that chaff releases may result in a significant decrease in downwind cloud-to-ground lightning. Another experimental approach is to use lasers to discharge lightning in an overhead cloud in order to divert the flash from striking people or highly sensitive equipment on the ground; more research is needed to make this a realistic method of lightning suppression. In the 1960s, seeding with silver iodide was considered in order to produce an excess of ice crystals to cause numerous coronal discharges within the thunderstorm and reduce the need for the flash to reach the ground, but the test results were complex and difficult to identify. Finally, electric space charge was released into the atmosphere from a network of high-voltage wires on the ground to produce corona discharge, but a field test showed minimal effects on suppressing lightning.
Industry:Weather
Probing the atmosphere above the earth's horizon from a satellite or other space vehicle. Measuring radiation emitted in the horizontal direction at various altitudes above the limb is a useful method for obtaining vertical profiles of atmospheric constituents.
Industry:Weather
Prediction of future hydrologic variables such as streamflow or snowmelt for periods of at least one week and up to several months in advance.
Industry:Weather
Popular term for a set of optical particle probes for counting, sizing, and/or imaging aerosols or hydrometeors, named for the inventor, Robert G. Knollenberg.
Industry:Weather
Part of the Kuroshio system. Between longitudes 155° and 160°E, considerable water turns south and southwest, forming part of the Kuroshio countercurrent. It runs at a distance of approximately 700 km from the coast as the eastern branch of a large whirl on the right-hand side of the Kuroshio.
Industry:Weather
