Meteorologija - Puslapis 5

(Darbą įkėlė Svečias)

Darbas:

just west of the Northern Mariana Islands. The eye wall descends almost to the sea surface, a distance of nearly 45,000 feet (13,800 meters).
Finally, there exists a group of clouds, rarely or occasionally observed, not included in the main classification.
Some of these "special clouds" consist for the greater part or in their entirety of non-aqueous liquid or solid particles. Included in the "special" clouds are the nacreous clouds, which by day resemble pale cirrus, but after sunset, are characterized by brilliant colors. They occur at altitudes between 21 and 30 kilometers (70,000 and 100,000 feet). The physical constitution of nacreous clouds is still unknown. Measurements have shown that their altitude ranges from 75 to 90 kilometers (250,000 to 300,000 feet). Their physical composition is also unknown, but they are believed to be composed of fine, cosmic dust particles possibly with a thin, outer layer of ice. Noctilucent clouds become visible after sunset.

Other special clouds include clouds from fires produced by the fine combustion products. These may appear as dark, cumulus or cumulonimbus clouds but usually are rapidly dispersed and carried great distances by the wind, spreading to resemble thin, stratiform veils. Clouds from volcanic eruptions, explosions, and industrial activities are also considered in the "special cloud" category.

2. CUMULONIMBUS CLOUDS IN DIFFERENT SINOPYICAL SITUATIONS

2.1 CLOUDS OF VERTICAL DEVELOPMENT

The bases of this type of cloud may form as low as 1500 feet. They are composed of water droplets when the temperature is above freezing and of ice crystals and super cooled water droplets when the temperature is below freezing.
Cumulus (Cu). Dense clouds of vertical development. They are thick, rounded and lumpy and resemble cotton balls. They usually have flat bases and the tops are rounded. They cast dense shadows and appear in great abundance during the warm part of the day and dissipate at night. When these clouds are composed of ragged fragments, they are called cumulus fractus.

Towering Cumulus (TCu). Cumulus clouds that build up into high towering masses. They are likely to develop into cumulonimbus. Rough air will be encountered underneath this cloud. Heavy icing may occur in this cloud type.

Cumulonimbus (Cb). These clouds are much larger and more vertically developed than cumulus clouds, which form, in a more stable atmosphere. They can exist as individual towers or form a line of towers called a squall line often present at cold fronts. Underneath they are dark and menacing. At a distance they rise up like huge White Mountains when the Sun shines on them, and are commonly topped with anvil-shaped heads.

To introduce and discuss the importance of cumulonimbus clouds,