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	Cloud condensation nuclei - Biocrawler (Site not responding. Last check: 2007-10-12)
		Cloud condensation nuclei or CCNs are small particles (typically 0.00002 mm, or 1/100 th the size of a cloud droplet [1] (http://apollo.lsc.vsc.edu/classes/met130/notes/chapter6/ccn.html)) about which cloud droplets coalesce.
		A typical raindrop is about 2 mm in diameter, a typical cloud droplet is on the order of 0.02 mm, and a typical cloud condensation nuclei (particle or droplet) is on the order of 0.0002 mm or 0.2 micrometer in diameter.
		The number and type of CCNs can affect the radiative properties of clouds as well as the amount and hence have an influence on climate change [2] (http://www.agu.org/revgeophys/rasmus00/node26.html) [3] (http://www.grida.no/climate/ipcc_tar/wg1/181.htm), but the details of this are still not well understood.
	www.biocrawler.com /encyclopedia/CCN (470 words)

	Britain.tv Wikipedia - Cloud condensation nuclei
		Cloud condensation nuclei or CCNs (also known as cloud seeds) are small particles (typically 0.0002 mm, or 1/100 th the size of a cloud droplet [1]) about which cloud droplets coalesce.
		A typical raindrop is about 2 mm in diameter, a typical cloud droplet is on the order of 0.02 mm, and a typical cloud condensation nucleus (aerosol) is on the order of 0.0001 mm or 0.1 micrometer or greater in diameter.
		The number and type of CCNs can affect the lifetimes and radiative properties of clouds as well as the amount and hence have an influence on climate change [2] [3], but the details of this are still not well understood but are the subject of much research by many groups worldwide.
	www.britain.tv /wikipedia.php?title=Cloud_condensation_nuclei (656 words)

	EO Library: Changing Global Cloudiness
		Clouds are visible collections of small particles of water or ice, or both, suspended in the atmosphere.
		Water vapor, or water in its gaseous state, is transferred from the surface to the atmosphere primarily via either evaporation or "evapotranspiration," (the process by which water is evaporated from the tiny openings on the leaves of plants during respiration).
		Since hygroscopic nuclei have an affinity for water, they act as "seeds" to accelerate the condensation process to convert water from its gaseous to its liquid phase.
	earthobservatory.nasa.gov /Library/GlobalClouds (325 words)

	Large-Eddy Simulations of Entrainment of Cloud Condensation Nuclei into the Arctic Boundary Layer: 18 May 1998 ...
		Three-dimensional simulations of a spring time Arctic boundary layer cloud observed during the FIRE/SHEBA 1998 spring IOP were conducted to study the influence of entrainment of cloud condensation nuclei (CCN) at cloud top on cloud microphysical and dynamical structure, radiative properties, and cloud evolution.
		The response of the cloud optical properties to entrainment occurs from the begining of the simulations.
		Cloud albedo shows a 12% increase, while cloud optical depth has a 33% increase due to the entrainment of higher CCN concentrations.
	rams.atmos.colostate.edu /may18/les.html (242 words)

	Introduction
		To investigate the effect of cloud microphysical processes on climate, it is therefore desirable to separate the dependence of cloud optical properties on droplet size distribution and liquid water content.
		It is found that cloud optical properties depend mainly on equivalent radius throughout the solar and terrestrial spectrum and are insensitive to the details of the droplet size distribution, such as shape, skewness, width and modality (single or bimodal).
		This suggests that in cloud models, aimed at predicting the evolution of cloud microphysics with climate change and conversely the impact of cloud microphysics on climate evolution, it is sufficient to determine the third and the second moments of the size distribution (the ratio of which determines the equivalent radius).
	asd-www.larc.nasa.gov /~yhu/paper/thesisall/node6.html (870 words)

	[No title]
		The larger the aerosol and the greater its solubility, the lower is the supersaturation required for the aerosol to serve as a cloud condensation nuclei.
		In contrast to cloud condensation nuclei, the most effective ice nuclei are hydrophobic having molecular spacings and a crystallographic structure close to that of ice.
		Optical Depth is a logarithmic measure of cloud turbidity (usually between 0 and 4) and is related to the size and number of particles in the cloud.
	www.geo.mtu.edu /~raman/hydrometeors.html (2213 words)

	AI Weather Modification Page
		Cloud and storm-related events which are often the target for cloud seeding programs include rainfall, snow, fog, lightning, hail and devastating winds from severe storms.
		Clouds are made up of billions of these tiny water droplets or ice crystals and sometimes combinations of both.
		Of prime importance for determining both the initiation and amount of precipitation from the cloud system are (1) the vertical and horizontal dimensions of the clouds, (2) the lifetime of the clouds and (3) the sizes and concentrations of cloud droplets and ice particles.
	www.atmos-inc.com /weamod.html (919 words)

	CO2 Science
		Cloud condensation nuclei are small particles in the atmosphere about which water vapor may condense to form clouds.
		Furthermore, cloud droplet spectra measured in the ship tracks showed higher number concentrations and lower droplet effective radii than spectra measured in adjacent non-ship-impacted clouds, both of which alterations typically make clouds brighter and more persistent and, therefore, better able to cool the part of the planet over which they float.
		The standard theory of cloud droplet creation, which is utilized in current IPCC climate projections, assumes that water droplets form around aerosol nuclei composed of soluble inorganic salts, and that the drops are activated, or grow spontaneously, after they reach a certain critical size in air that is supersaturated with water vapor.
	www.co2science.org /scripts/CO2ScienceB2C/subject/c/summaries/ccn.jsp (1719 words)

	IGAC \| Measurements and Modeling of Atmospheric Methane Using Stable Carbon Isotopes
		The indirect climatic effect of aerosols refers to the influence of aerosols on cloud optical depth and albedo, and cloud lifetime, as a result of anthropogenic changes in the number and composition of cloud condensation nuclei (CCN).
		The large uncertainty attending indirect forcing exists because of the complex sequence of phenomena that connects aerosols with CCN, CCN with cloud droplets, and cloud droplets with cloud albedo and cloud lifetime.
		The relationship between CCN measurements obtained with the various instruments and activation in cloud-forming regions of the atmosphere remains unclear.
	www.igac.noaa.gov /newsletter/17/cloud.php (2133 words)

	NASA: TERRA (EOS AM-1) - About Terra
		Clouds reflect solar radiation, which tends to cool the climate, but they also help contain the energy that the Earth would otherwise emit to space, which tends to warm the climate.
		Net cloud forcing is the result of two opposing effects: (1) greenhouse heating by clouds (or positive forcing) — clouds trap heat coming from Earth's surface that would otherwise be lost to space, and (2) cooling by clouds (or negative forcing) — clouds reflect incoming solar radiation back to space.
		Because clouds change rapidly over short time and space intervals, they are difficult to simulate in computer models and, therefore, their contribution to climate change is difficult to quantify.
	terra.nasa.gov /FactSheets/Clouds (1371 words)

	Absorption - Uptake of Radiation
		The point at which this condensation occurs within the moistened air is when the air is saturated with water vapor, which means it cannot hold more water in the form of vapor.
		First, a large number of particles are incorporated in the condensed phase of the cloud, as cloud condensation nuclei or ice forming nuclei.
		Clouds are formed when the relative humidity in the air is higher than 100%.
	www.espere.net /Unitedkingdom/water/uk_cloudform.htm (1671 words)

	Cloud Condensation Nuclei (CCN) Calculator (Site not responding. Last check: 2007-10-12)
		Introduction : This calculator calculates the number of nuclei of a certain radius size in a volume of air with a concentration of c.
		Cloud Condensation Nuclei or CCN are the basis of cloud formation.
		The algorithm for the number density of the cloud condensation nuclei is:
	www.shodor.org /os411/courses/_master/tools/calculators/ccn/index.html (89 words)

	Atmospheric Cloud Condensation Nuclei (Site not responding. Last check: 2007-10-12)
		The degree of brightening in these clouds is sensitive to the cloud droplet concentration, which depends upon the CCN available.
		To measure CCN, aerosol must be subjected to a supersaturated environment, which is commonly done with a thermal diffusion chamber.
		The CCN counter subjects the sample to a specified supersaturation and records the number of aerosol that become CCN.
	www.cgc.uaf.edu /Newsletter/gg6_1/cloud.html (616 words)

	MMM ASR 2002 - Research
		The foci of studies on chemistry, aerosols, and dynamics interactions are to examine the effect of physical and dynamical processes on chemical species and to study the effect of chemistry on aerosols and cloud condensation nuclei.
		The activation and growth of cloud drops are simulated by a cloud parcel model that represents a spectrum of cloud condensation nuclei.
		The cloud chemistry is simulated as 1) a bulk water calculation with drop radius set to ten microns, and 2) a population of drops with varying sizes.
	www.mmm.ucar.edu /asr2003/chemistry.html (877 words)

	Global Monitoring Division (Site not responding. Last check: 2007-10-12)
		A balloon-borne instrument was constructed for observations of vertical profiles of cloud condensation nucleus (CCN) concentrations, active at 1% supersaturation.
		CCN concentrations exhibited a general decrease from the surface to the top of the boundary layers, were generally uniform through well-mixed layers, and show variability above well-mixed layers.
		In general, the structure of the CCN profile appears to be closely related to the structure in the CN and D
	wwwsrv.cmdl.noaa.gov /aero/personnel/ddelene/ccn_abstract.html (203 words)

	biology - Cloud condensation nuclei (via CobWeb/3.1 planetlab2.netlab.uky.edu) (Site not responding. Last check: 2007-10-12)
		Cloud condensation nuclei or CCNs are small particles (typically 0.00002 mm, or 1/100 th the size of a cloud droplet [1]) about which cloud droplets coalesce.
		Without CCNs, water vapour can be strongly supercooled before droplets spontaneously form (this is the basis of the cloud chamber for detecting subatomic particles).
		The number and type of CCNs can affect the radiative properties of clouds as well as the amount and hence have an influence on climate change [2] [3], but the details of this are still not well understood.
	www.biologydaily.com.cob-web.org:8888 /biology/Cloud_condensation_nuclei (344 words)

	AMS Glossary
		Cloud differs from fog only in that the latter is, by definition, close (a few meters) to the earth's surface.
		Clouds form in the free atmosphere as a result of condensation of water vapor in rising currents of air, or by the evaporation of the lowest stratum of fog.
		Generally, cloud drops (droplets) range from 1–100 μm in diameter, and hence are very much smaller than raindrops.
	amsglossary.allenpress.com /glossary/search?id=cloud1 (133 words)

	Cloud Formation and Explicit Precipitation
		Clouds are formed as air parcels are forced to rise, cool and condense.
		Clouds condense when relative humidity is > 75% for land and > 80% for ocean.
		Cloud parameterization scheme predicts cloud liquid and ice based on RH and temperatures in each model layer.
	www.met.tamu.edu /class/metr452/models/2001/precip.html (1124 words)

	SatMet - Cloud Formation
		Liquid particles suspended in the atmosphere are referred to as cloud droplets and the solid particles are often called ice crystals.
		Layered clouds form in more stable environments in which large layers of air are slowly lifted.
		Clouds reflect shortwave solar energy back into space and tend to cool the earth.
	cimss.ssec.wisc.edu /satmet/modules/clouds/cloudformation.html (325 words)

	Reference.com/Encyclopedia/Cloud condensation nuclei
		Cloud condensation nuclei or CCNs (also known as cloud seeds) are small particles (typically 0.0002 mm, or 1/100 th the size of a cloud droplet
		The number of cloud condensation nuclei in the air can be measured and ranges between around 100 to 1000 per cubic centimeter.
		The number and type of CCNs can affect the lifetimes and radiative properties of clouds as well as the amount and hence have an influence on climate change
	www.reference.com /browse/wiki/Cloud_condensation_nuclei (624 words)

	Dimethylsulfide Emission: Climate Control by Marine Algae
		Clouds affect the Earths radiation balance and thereby greatly influence its temperature and climate.
		A cloud's optical properties are related to the size distribution and number of its droplets.
		The more cloud condensation nuclei, the smaller the size of its water droplets and the higher the density of water droplets since the same amount of water vapor is distributed among a greater number of CCN.
	www.csa.com /discoveryguides/dimethyl/overview.php/t_blank (2658 words)

	Winter 2004 - p. 3
		The objective is to learn what CCN occur naturally or are already in place within a cloud from a source such as a smokestack.
		Cloud seeding conducted as part of Weather Modification programs generally uses silver iodide that is introduced into the cloud from burning flares as nuclei around which water drops can form, thus speeding up the process of rain formation.
		The aircraft takes samples of air that is then analyzed for water droplets, their sizes, and the types of naturally occurring or human produced CCN that are in the cloud.
	www.npwd.org /winter_2004_-_page_3.htm (539 words)

	Global Monitoring Division (Site not responding. Last check: 2007-10-12)
		The research objective was to obtain high-vertical resolution profiles of CCN concentration from the surface to 200 mb and relate these measurements to concurrent measurements of condensation nuclei, optical aerosols, and meteorological conditions.
		The uncertain in CCN mesurements, made with the balloon-borne CCN counter, was determined.
		Several vertical profiles of CCN concentration have been obtained at Laramie, Wyoming and two profiles obtained at Lauder, New Zealand.
	wwwsrv.cmdl.noaa.gov /aero/personnel/ddelene/dissertation.html (157 words)

	Keith Broekhuizen
		Clouds and cloud droplets play a very important role in the earth’s atmosphere and climate system.
		The way in which atmospheric particles, both natural and man-made, impact the formation, lifetime, and properties of clouds is of vital importance in the prediction of climate effects.
		The uptake of water vapor on particles and the subsequent cloud droplet formation will be studied using tandem differential mobility analysis and a thermal gradient cloud chamber.
	www.colgate.edu /desktopdefault1.aspx?tabid=2121 (538 words)

	ISWS - Publications Search - Publication Abstract
		The goal of the project is to develop the instrumentation to collect cloud condensation nuclei (CCN) in sufficient amounts to determine their chemical composition, and to survey the CCN composition in different climates through a series of field measurements.
		Our approach to CCN collection is to first form droplets on the nuclei under simulated cloud humidity conditions, which is the only known method of identifying CCN from the background aerosol.
		Two size fractions of CCN particles are collected by first forming droplets on the larger CCN in a haze chamber at 100 percent relative humidity, then activating the remaining CCN at 1 percent supersaturation in a cloud chamber.
	www.sws.uiuc.edu /pubs/abstract.asp?PID=1580 (253 words)

	Researchers improve predictions of cloud formation for better climate modeling (Site not responding. Last check: 2007-10-12)
		Scientists have tried to predict cloud formation through empirical “parameterization” – techniques that rely on empirical information or correlations, such as comparing the number of particles in the atmosphere with the number of cloud droplets.
		A new type of cloud condensation nuclei (CCN) counter was developed by Georgia Tech Assistant Professor Athanasios Nenes and Gregory Roberts at the Scripps Institution of Oceanography.
		The CCN counter is being commercialized by Droplet Measurement Technologies in Boulder, Colo., and a number of research universities and government agencies have already placed orders.
	gtresearchnews.gatech.edu /newsrelease/cloudcover.htm (1202 words)

	2000 Progress Report - AIRBORNE MEASUREMENTS OF CLOUD CONDENSATION NUCLEI (Site not responding. Last check: 2007-10-12)
		The goal of this research is to develop an effective instrument for accurately classifying cloud condensation nuclei (CCN) according to their critical supersaturation.
		The CCN measurement is a very sensitive one- the supersaturation range of interest is generally ranges from 0.01% to 1%.
		In order to gain a better understanding of the complex interactions involved in CCN activation, detailed simulations of the performance of the new instrument will be used in conjunction with the rest of the design process.
	es.epa.gov /ncer/fellow/progress/98/vanrekenti00.html (297 words)

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