- 行业: 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, ...
A line drawn through all points on a map having the same amount of cloudiness. See nephanalysis, nephcurve.
Industry:Weather
A line (or transition zone) that encircles the earth and lies between two belts that typify the annual time distribution of rainfall in the lower latitudes of each hemisphere; a form of meteorological equator. It lies slightly north of the geographic equator, reaching its most northerly position at about 10°N latitude near the mouth of the Orinoco River in South America. The hyetal equator is more or less centrally situated in the belt of tropical rainfall, which has two rainy seasons and generally one main dry season, the latter occurring in the winter of the corresponding hemisphere.
Industry:Weather
A line connecting points of equal change in temperature within a given time period.
Industry:Weather
A line connecting points having the same vertical direction (inclination) of a particular vector quantity. This term is not widely used in this sense, probably because of its long-standing geological definition relating to folded rock strata. See isoclinic line; compare isogon.
Industry:Weather
A lightning discharge occurring between a positive charge center and a negative charge center, both of which lie in the same cloud; starts most frequently in the region of the strong electric field between the upper positive and lower negative space charge regions. In summer thunderstorms, intracloud flashes precede the occurrence of cloud-to-ground flashes; they also outnumber cloud-to-ground flashes. Intracloud lightning develops bidirectionally like a two-ended tree: one end of the tree is a branching negative leader, the other is a branching positive leader. Later in the flash, fast negative leaders similar to dart leaders (also called K changes) appear in the positive end region and propagate toward the flash origin. In weather observing, this type of discharge is often mistaken for a cloud-to-cloud flash, but the latter term should be restricted to true intercloud discharges, which are far less common than intracloud discharges. Cloud discharges tend to outnumber cloud-to-ground discharges in semiarid regions where the bases of thunderclouds may be several kilometers above the earth's surface. In general, the channel of a cloud flash will be wholly surrounded by cloud. Hence the channel's luminosity typically produces a diffuse glow when seen from outside the cloud, and this widespread glow is called sheet lightning.
Industry:Weather
A layer of ice on top of some other feature. Usually used in reference to an ice layer at the surface of a lake or pond.
Industry:Weather
A layer of haze in the atmosphere, usually bounded at the top (haze line) by a temperature inversion and frequently extending downward to the ground. Necessary for the existence of this phenomenon are, of course, a source of haze particles and a relatively stable stratification of temperature in the atmosphere either within or immediately above the haze layer. A haze layer may vary in extent from the type developed locally over an urban area at night to a layer covering thousands of square miles as within an old and stable air mass.
Industry:Weather
A large, level area of ice, either of sea ice (“more than five miles across”) or an ice cap or highland ice.
Industry:Weather
A large mass of floating or stranded ice that has broken away from a glacier; usually more than 5 m above sea level. The unmodified term “iceberg” usually refers to the irregular masses of ice formed by the calving of glaciers along an orographically rough coast, whereas tabular icebergs and ice islands are calved from an ice shelf, and floebergs are formed from sea ice. In decreasing size, they are classified as: ice island (few thousand square meters to 500 km2 in area); tabular iceberg; iceberg; bergy bit (less than 5 m above sea level, between 1 and 200 m2 in area); and growler (less than 1 m above sea level, about 20 m2 in area).
Industry:Weather
