Cloud formation mechanisms

The mechanism of Self-organized criticality, a concept first introduced by Bak, Tang and Wiesenfeld [bak87a], may possibly provide a fundamental link between such temporal scale invariant phenomena and phenomena exhibiting a spatial scale invariance - familiar examples of which are given by fractal coastlines, mountain landscapes and cloud formations [mandel82],... 

This overview will outline surfactant mixture properties and behavior in selected phenomena. Because of space limitations, not all of the many physical processes involving surfactant mixtures can be considered here, but some which are important and illustrative will be discussed these are micelle formation, monolayer formation, solubilization, surfactant precipitation, surfactant adsorption on solids, and cloud point Mechanisms of surfactant interaction will be as well as mathematical models which have been be useful in describing these systems,... 

Effect of aerosol particles on cloud drop number concentrations and size distributions Clouds and fogs are characterized by their droplet size distribution as well as their liquid water content. Fog droplets typically have radii in the range from a few /an to 30-40 /an and liquid water contents in the range of 0.05-0.1 g m" Clouds generally have droplet radii from 5 /an up to 100 /im, with typical liquid water contents of 0.05-2.5 gin"5 (e.g., see Stephens, 1978, 1979). For a description of cloud types, mechanisms of formation, and characteristics, see Wallace and Hobbs (1977), Pruppacher (1986), Cotton and Anthes (1989), Heyms-field (1993), and Pruppacher and Klett (1997). 

Fractionation correlation techniques have been applied to cloud, fallout, and ground-filter samples from the Transient Nuclear Test of January 1965. Although safety analysts do not consider fractionation effects to be of operational importance for this type of event, analysis of such data provides insight into the mechanisms of debris formation. The results show many similarities to the correlations observed for fallout. Those dissimilarities found indicate the importance of escape processes to the formation mechanisms for this type of debris. 

In summary it seems that in situ synthesis of long chain carbon molecules is presently the most convincing of the various formation mechanisms. In particular, spallation of organic grains s ms rather unlikely in the cold dark clouds such as TMC 1. We note, incidentally, that the dark clouds produce an absolutely clean chemistry , in the sense that many types of reactions which occur in terrestrial chemistry are excluded. Shocks, for example, appear not to be present if one can judge from the observed narrow line profiles. The gas is very quiescent and cold. On the other hand, ions such as HCO and (Guelin et al., 1977)... 

The mechanism of cloud formation (Mason, 1971) is the cooling of moist air below its... 

Many kinds of organic molecules liave been detected in interstellar clouds. The formation mechanisms of these molecules have been one of the most significant issues in cosmochemistiy. Recent tlieoretical and experimental studies suggest that tlie important mechanisms are ion-molecular reactions in tlie gas phase [59], grain surface reaction in dusts [60], gas-pliase pyrolysis [61], and photochemical reaction in icy grain mantles [62]. The ion-molecular reaction results from a collision of ions and molecules in a gas phase. Because of tlie lack... 

Peter, T. (1996) Formation mechanisms of polar stratospheric clouds, in Nucleation and Atmospheric Aerosols 1996, M. Kulmala and P. E. Wagner, eds., Elsevier, Oxford, UK, pp. 280-291. 

The ability of a given particle to become activated depends on its size and chemical composition and on the maximum supersaturation experienced by the particle. If, for example, the ambient RH does not exceed 100%, no particle will be activated and a cloud cannot be formed.2 In this section we will examine the mechanisms by which clouds are created in the atmosphere. A necessary condition for this cloud formation is the increase in the RH of an air parcel to a value exceeding 100%. This RH increase is usually the result of cooling of a moist air parcel. Even if the water mass inside the air parcel does not change, its saturation water vapor concentration decreases as its temperature decreases, and therefore its RH increases. 

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