- 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, ...
Multiple generations of secondary cosmic rays produced when primary cosmic rays interact with atoms in the upper atmosphere, yielding subatomic particles and gamma rays. The secondary cosmic rays in turn produce even more down through the atmosphere. Billions of these particles travel downward at nearly the speed of light and at ground level may extend over several square kilometers (in which instance the shower may be termed an extensive air shower). The maximum flux of cosmic rays, both primary and secondary, is at an altitude of 20 km, and below this the absorption by the atmosphere reduces the flux, though the rays are still readily detectable at sea level. Intensity of cosmic ray showers has also been observed to vary with latitude, being more intense at the poles.
Industry:Weather
A project that reconstructed global climate at several times in the Holocene, using pollen, lake-level, and marine microfossils. These reconstructions were compared with general circulation model results using the boundary conditions appropriate to each time in order to investigate the global effects of variations in insolation resulting from the Milankovitch variations and the effects of the retreating continental ice sheets in the early Holocene.
Industry:Weather
A project that reconstructed sea surface temperatures 18 000 years before present (BP). The temperature information was derived from properties of deep-ocean sediments sampled by means of corers, and provided strong support for the role of Milankovitch variations as a pacemaker for climate fluctuations. The primary attributes used were the species composition of planktonic organisms found in the sediments, and the oxygen isotopic composition of foraminiferan skeletons.
Industry:Weather
A composite radar display constructed by assembling radar data from many PPIs at successive elevation angles to obtain the pattern of the data at a specified constant altitude.
Industry:Weather
(Abbreviated CZCS. ) A scanning radiometer with six channels flown on Nimbus 7 (launched October 1978) designed to monitor ocean color and phytoplankton production in coastal areas. Four channels are in the visible part of the spectrum, one in the near-infrared, and one in the thermal infrared.
Industry:Weather
A type of radar that transmits continuously instead of in pulses. Moving targets may be recognized with such radars by observing a Doppler shift in the frequency of the received signal. Some forms of modulation of the transmitted wave allow measurement of range (e.g., FM–CW radar). Historically, continuous-wave radars preceded the development of the pulsed radars widely used today.
Industry:Weather
A principal cloud type (cloud genus) in the form of individual, detached elements that are generally dense and posses sharp nonfibrous outlines. These elements develop vertically, appearing as rising mounds, domes, or towers, the upper parts of which often resemble a cauliflower. The sunlit parts of these clouds are mostly brilliant white; their bases are relatively dark and nearly horizontal. Near the horizon the vertical development of cumulus often causes the individual clouds to appear merged. If precipitation occurs, it is usually of a showery nature. Various effects of wind, illumination, etc. , may modify many of the above characteristics. Strong winds may shred the clouds, often tearing away the cumulus tops to form the species fractus. Under certain conditions cumulus clouds may be arranged in files, cloud streets, oriented approximately parallel to the wind direction. Changes in direction of illumination and in background cause modification of color and of apparent surface relief. Cumulus is composed of a great density of small water droplets, frequently supercooled. Within the cloud larger water drops are formed that may, as the cloud develops, fall from the base as rain or virga. Ice crystal formation will occur within the cloud at sufficiently low temperatures, particularly in upper portions as the cloud grows vertically. Occasionally the growth of ice crystals at the expense of water droplets will reduce the entire cloud to diffuse trails of snow. Cumulus most often forms directly in clear air as a result of convection in air of sufficiently high moisture content for a condensation level to be reached. As a result, a distant diurnal cycle of cumulus frequency is observed. Over a landmass, the cumulus maximum occurs after midday (for a horizontal extent, early afternoon; for vertical extent, somewhat later). Over a water surface, the cycle is reversed and much less obvious, with the cumulus maximum generally recognized as occurring after midnight. The vertical growth of a cumulus cell is restricted and modified by the existence and character of layers of relative static stability above the cloud base. Cumulus may also evolve from the convective transformation of stratus or stratocumulus (Cu stratomutatus or Cu stratocumulomutatus). Cumulus may be generated by altocumulus and, again, stratocumulus (Cu altocumulogenitus and Cu stratocumulogenitus). Cumulonimbus is the ultimate manifestation of the growth of cumulus; therefore, at a certain point, it is difficult to differentiate between the two. If a cloud in doubt reveals no fibrous structure, it is still cumulus; if still in doubt, cumulonimbus further differs in that it is accompanied by lightning, thunder, and sometimes hail. The elements of altocumulus are smaller and, along with those of stratocumulus, tend to be more merged than the separated units of cumulus. Cumulus has the unique ability to penetrate other preexisting cloud layers, sometimes partially dissipating, at other times apparently fusing with, the impaled layers. The cumulus, in this instance, retains its identity as long as it remains primarily vertically developed, is physically (although perhaps not visibly) separate from the other cloud, and has a tower- or dome-shaped summit. See cloud classification, trade-wind cumulus.
Industry:Weather
An electronic instrument designed to measure very accurate, nearly continuous profiles of conductivity, temperature, and pressure (depth) in the water column. It is usually lowered on the end of a conducting cable through which the real-time measurements are transmitted to a recorder on the ship. Today there are also self-contained instruments (i.e., with an internal memory). Salinity is computed subsequently from the conductivity and temperature measurements. Accuracies are typically ±0. 005 psu, 0. 005 K, and 0. 15% full scale for conductivity, temperature, and depth, respectively.
Industry:Weather
A branch of cognitive science devoted to identifying the processes involved in performing a task requiring intelligence. CTA is useful in the design of expert systems, computer interfaces, and the appropriate division of tasks between humans and computers. A recent CTA of weather forecasting in the Air Force has resulted in modifications to the forecast office and in forecaster and observer training.
Industry:Weather
A principal cloud type (cloud genus), appearing as a whitish veil, usually fibrous but sometimes smooth, that may totally cover the sky, and that often produces halo phenomena, either partial or complete. Sometimes a banded aspect may appear, but the intervals between the bands are filled with thinner cloud veil. The edge of a veil of cirrostratus may be straight and clear-cut, but more often it is irregular and fringed with cirrus. Some of the ice crystals that compose the cloud are large enough to fall and thereby produce a fibrous aspect. Cirrostratus occasionally may be so thin and transparent as to render it nearly indiscernible, especially through haze or at night. At such times, the existence of a halo may be the only revealing feature. The angle of incidence of illumination upon a cirrostratus layer is an important consideration in evaluating the identifying characteristics. When the sun is high (generally above 50° elevation), cirrostratus never prevents the casting of shadows by terrestrial objects; and a halo might be completely circular. At progressively lower angles of the sun, halos become fragmentary and light intensity noticeably decreases. Cirrostratus may be produced by the merging of elements of cirrus (Cs cirromutatus); from cirrocumulus (Cs cirrocumulogenitus); from the thinning of altostratus (Cs altostratomutatus); or from the anvil of cumulonimbus (Cs cumulonimbogenitus). Since cirrostratus and altostratus form from each other, it is frequently difficult to delineate between the two. In general, altostratus does not cause halo phenomena, is thicker than cirrostratus, appears to move more rapidly, and has a more even optical thickness. When near the horizon, cirrostratus may be impossible to distinguish from cirrus. See cloud classification, cirriform.
Industry:Weather
