Cirrus clouds

There are three fundamental classes of clouds cirrus, cumulus, and stratus. Cirrus are high clouds with a silken appearance, becattse they are composed of ice crystals. Cumulus are detached, dertse clouds that rise in motmds or towers from a level base. Stratus is the name given to an extensive layer or flat patches of low clouds showing hardly any well-defined detail. These names are some-... 

Clouds cover roughly two-thirds of our earth s surface and play an important role in influencing global climate by affecting the radiation budget. Cirrus clouds are one example of a cloud type whose optical properties are not accurately known. Cirrus clouds form in the upper troposphere and are composed almost exclusively of non-spherical ice crystal particles. The impact of cloud coverage on dispersion of pollution in the atmosphere is an area of great concern and intensive study. 

Solar beating of tropical oceans warms the surface water, promoting evaporation. Where the equatorial surface waters are warmest and the northeast and southeast trade winds meet, a band of cirrostratus and cirrus clouds spreads out from convective precipitation regions. This area is known as the Intertropical Convergence Zone. 

Since feedbacks may have a large potential for control of albedo and therefore temperature, it seems necessary to highlight them as targets for study and research. Besides the simple example above of cloud area or cloud extent, there are others that can be identified. High-altitude ice clouds, for example, (cirrus) have both an albedo effect and a greenhouse effect. Their occurrence is very sensitive to the amount of water vapor in the upper troposphere and to the thermal structure of the atmosphere. There may also be missing feedbacks. 

Borrmann, S S. Solomon, L. Aval lone, D. Toohey, and D. Baumgardner, On the Occurrence of CIO in Cirrus Clouds and Volcanic Aerosol in the Tropopause Region, Geophys. Res. Lett., 24, 2011-2014 (1997a). 

Number concentrations of ice crystals in cirrus clouds have also been observed to increase with aerosol particle concentrations (with diameters >0.018 /tm) and, in particular, with the concentration of light-absorbing materials in the ice crystals (Strom and Ohlsson, 1998). 

Fu, R., A. D. Del Genio, W. B. Rossow, and W. T. Liu, Cirrus-Cloud Thermostat for Tropical Sea Surface Temperatures Tested Using Satellite Data, Nature, 358, 394-397 (1992). 

Heymsfield, A. J., Microphysical Structures of Stratiform and Cirrus Clouds, in Aerosol-Cloud-Climate Interactions (P. V. Hobbs, Ed.), pp. 97-121, Academic Press, San Diego, 1993. 

Laaksonen, A., J. Hienola, M. Kulmala, and F. Arnold, Supercooled Cirrus Cloud Formation Modified by Nitric Acid Pollution of the Upper Troposphere, Geophys. Res. Lett., 24, 3009-3012 (1997). 

Ramanathan, V., and W. Collins, Thermodynamic Regulation of Ocean Warming by Cirrus Clouds Deduced from Observations of 1987 El Nino, Nature, 351, 27-32 (1991). 

Ramaswamy, V., and V. Ramanathan, Solar Absorption by Cirrus Clouds and the Maintenance of the Tropical Upper Troposphere Thermal Structure, J. Atmos. Sci., 46, 2293-2310 (1989). 

Strom, J., and S. Ohlsson, In Situ Measurements of Enhanced Crystal Number Densities in Cirrus Clouds Caused by Aircraft Exhaust, J. Geophys. Res., 103, 11355-11361 (1998). 

Clouds that are formed when the dew point is below the freezing point Cirrus... 

Cirrus clouds - high, thin, feathery clouds... 

Many uncertainties also remain about the impact of present changes in extra-atmospheric insolation on climate. Soon et al. (2000) detected, for instance, the super-sensitivity of the climate system to changes in UV insolation whose impact is enhanced by the feedback due to the statistical stability of clouds, influence of tropical cirrus clouds, and stratospheric ozone (the ozone-climate problem needs special analysis) (Kondratyev and Varotsos, 2000). 

This happened because of our investigation of the rate of nucleation of ice in deeply supercooled water. Previous laboratory studies of the freezing of water occurred in substantially warmer water and were blind to the phase of ice obtained. We studied water undergoing nucleation at roughly the temperature of nucleation in cirrus clouds, I believe. I understand that what happens in cirrus clouds has an important effect on the climate. Moreover, we showed directly that the ice first nucleated was the metastable cubic ice, not the ordinary hexagonal ice. Atmospheric scientists had inferred that result from indirect evidence. Previously it had not been possible to carry out experiments like ours in the laboratory, which is why our work attracted the attention of atmospheric scientists. 

Demott P. (2002) Laboratory studies of cirrus cloud processes. In Cirrus (eds. D. K. Lynch, K. Sassen, D. O C. Starr, and G. Stephens). Oxford University Press, Oxford, pp. 102-135. 

Cloud types often are classified based on altitude. High clouds have their bases above 7 km (23,000 ft) and include the wispy mare s tail clouds known as cirrus the cirrocumulus, known as mackerel sky and the layers of cirro-stratus. Middle clouds have altitudes between 2 and 7 km (6500 to 23,000 ft), and are either the rounded altocumulus or the layered altostratus. Low clouds have bases from near Earth s surface to about 2 km (6500 ft), and include stratocumulus, stratus, and nimbostratus. Nimbostratus clouds usually bring rain or snow. Clouds with vertical development extend from about 2 to 7 km or more, and include cumulonimbus (thunderhead clouds) and cumulus. 

Mangold, A., R. Wagner, H. Saathoff, U. Sehurath, C. Giesemann, V. Ebert, M. Kramer and O. Mohler Experimental investigation of iee nueleation by different types of aerosols in the aerosol chamber AIDA implications to microphysics of cirrus clouds, MeteoroL Z. (2004) accepted for pubUcatioiL... 

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