- 行业: Weather
- Number of terms: 60695
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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, ...
A cloud seeding operation in which an excess of nucleating material is released over that required to produce the desired effect. As the term is normally used, the excess is relative to that amount of nucleating material expected to produce the maximum amount of precipitation received at the ground. For example, in seeding a supercooled water cloud with dry ice or silver iodide in order to increase precipitation, the addition of too much seeding material will create too many ice crystals insofar as they compete for the available water vapor, and few of them will grow large enough to fall as precipitation. There are unresolved questions about what composes the optimal amount of seeding material to produce the desired effect. These questions include how to estimate the right amount of material and when and where to deliver it to the cloud; it is difficult to assign quantitative values that will result in overseeding. See cloud seeding.
Industry:Weather
1. Excess water that spills over the ordinary confines of a body of water. 2. A current exiting across the sill of a basin.
Industry:Weather
An aircraft flight so planned and navigated that it is completed under the optimum conditions of minimum time and minimum exposure to dangerous flying weather. An optimum flight often is not a minimal flight.
Industry:Weather
A warm southerly wind on the Bulgarian coast; it is considered a precursor of bad weather. See austru; compare lodos.
Industry:Weather
The quantity that is delivered by an instrument or a component of an instrument; used in contradistinction to the input.
Industry:Weather
1. Descriptive of a sky cover of 1. 0 (95% or more) when at least a portion of this amount is attributable to clouds or obscuring phenomena aloft; that is, when the total sky cover is not due entirely to surface-based obscuring phenomena. In aviation weather observations, an overcast sky cover is denoted by the symbol “symbol”; it may be explicitly identified as thin (predominantly transparent); otherwise a predominantly opaque status is implicit. An opaque overcast sky cover always constitutes a ceiling. See obscuration. 2. Popularly, the cloud layer that covers most or all of the sky. It generally suggests a widespread layer of clouds such as that considered typical of a warm front.
Industry:Weather
Issued to indicate that a hazardous weather or hydrologic event may develop. It is intended to provide information to those who need considerable lead time to prepare for the event.
Industry:Weather
Nocturnal cold-air jet flowing out of the mouth of a valley or canyon as it opens onto a plain. When the flow is fully developed, its depth near the exit is about the same as the height of the valley or canyon sidewalls there. It represents a continuation or extension of the mountain (downvalley or downcanyon) breeze generated in the valley by surface cooling. The jet often achieves peak wind speeds outside the valley. This acceleration is probably due to the conversion of potential to kinetic energy, as the column of cold air flowing out of the valley, freed of the confining sidewalls, fans out in the horizontal and compresses vertically. Another factor is the release of the flow from surface friction along the sidewalls. Maximum speeds in the jet begin near the surface early in the evening, but for well-developed jets at exits from deep valleys the highest speeds may be at 300–500 m or more above the ground. In deep, extensive valley drainage systems, peak speeds may exceed 10 m s<sup>−1</sup> on clear nights.
Industry:Weather
The radiative character of energy radiated from the warmer earth to cooler space, often derived from window channel measurements from satellites in polar orbit.
Industry:Weather
A valley glacier that drains an ice sheet or ice cap and flows through a gap in peripheral mountains.
Industry:Weather
