Darbas:
lacunosusStratus Nebulosus, fractus Opacus, translucidus, undulatus
Cumulus Humulis, mediocris, congestus, fractus radiatus
Cumulonimbus Calvus, capillatus
ETAGE CLOUD GENERA HIGHT
Tropical Region Temperate Region Polar Region
High CirrusCirrostratusCirrocumulus 20,000-60,000 ft 16,000-45,000ft 10,000-26,000ft
Middle AltostratusAltocumulus 6,500-26,000 ft 6,500-23,000 ft 6,500-13,000ft
Low StratusStratocumulusNimbostratusCumulusCumulonimbus 0-6,500 ft 0-6,500 ft
By convention, the part of the atmosphere in which clouds are usually present has been vertically divided into three "étages": high, middle and low. The base of the following cloud genera is normally found in the étage indicated:
Surface and aircraft observations have shown that clouds are generally encountered over a range of altitudes varying from sea level to the level of the tropopause, i.e. to 18 kilometers (60,000 feet) in the tropics, 13 kilometers (45,000 feet) in middle latitudes
1.2 THE HIGHT OF TROPOPAUSE
The height of the tropopause depends on the location, notably the latitude. It also depends on the season. Thus, it is about 16 km high over Australia at year-end, and between 12 - 16 km at midyear, being lower at the higher latitudes. At latitudes above 60, the tropopause is less than 9 -10 km above sea level; the lowest is less than 8 km high, above Antarctica and above Siberia and northern Canada in winter. The highest average tropopause is over the oceanic warm pool of the western equatorial Pacific; about 17.5 km high, and over Southeast Asia, during the summer monsoon, the tropopause occasionally peaks above 18 km. In other words, cold conditions lead to a lower tropopause, obviously because of less convection. Deep convection (thunderstorms) in the Intertropical Convergence Zone, or over mid-latitude continents in summer, continuously push the tropopause upwards and as such deepen the troposphere. This is because thunderstorms mix the tropospheric air at a moist adiabatic lapse rate.
In the upper troposphere, this lapse rate is essentially the same as the dry adiabatic rate of 10K/km. So a deepening by 1 km reduces the tropopause temperature by 10K. Therefore, in areas where (or at times when) the tropopause is exceptionally high, the tropopause temperature is also very low, sometimes below -80° C. Such low temperatures are not found anywhere else in the Earth's atmosphere, at any level, except in the winter stratosphere over Antarctica.
On the other hand, colder regions have a lower tropopause, obviously because convective overturning is limited there, due to the negative radiation balance at the surface. In fact, convection is very rare in Polar Regions; most of the tropospheric
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