Liquid cloud types

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). 

FIGURE 7.2 Frequency distribution for liquid water content average values for various cloud types over Europe and Asia. 

Cloud Type Droplet Concentration (cm ) Liquid Water (g m" ) Mean Droplet Size (/im)... 

Liquid water contents are dependent on the cloud type, cloud base temperature, and height above cloud base. In stratiform clouds, the values are comparatively low, usually 0.1 g m . In cumulus clouds, typical peak values are 0.5 g m , which increase with increasing cloud intensity to more than 3 g m for severe thunderstorms. (As the cloud base temperature increases, a cloud of a given type tends to have a higher liquid water content, increasing with height from cloud base to near cloud top and then falling abruptly to zero at cloud top.)... 

The equivalent charge weight of TNT is calculated on the basis of the entire cloud content. FMRC recommends that a material-dependent yield factor be applied. Three types of material are distinguished Class I (relatively nonreactive materials such as propane, butane, and ordinary flammable liquids) Class II (moderately reactive materials such as ethylene, diethyl ether, and acrolein) and Class III (highly reactive materials such as acetylene). These classes were developed based on the work of Lewis (1980). Energy-based TNT equivalencies assigned to these classes are as follows ... 

A vessel filled with a pressurized, superheated liquid can produce blasts upon bursting in three ways. First, the vapor that is usually present above the liquid can generate a blast, as from a gas-filled vessel. Second, the liquid will boil upon depressurization, and, if rapid boiling occurs, a blast wiU result. Third, if the fluid is combustible and the BLEVE is not fire induced, a vapor cloud explosion may occur (see Section 4.3.3.). In this subsection, only the first and second types of blast wiU be investigated. 

Boiling-liquid expanding-vapor explosion (BLEVE) A BLEVE occurs if a vessel that contains a liquid at a temperature above its atmospheric pressure boiling point ruptures. The subsequent BLEVE is the explosive vaporization of a large fraction of the vessel contents possibly followed by combustion or explosion of the vaporized cloud if it is combustible. This type of explosion occurs when an external fire heats the contents of a tank of volatile material. As the tank contents heat, the vapor pressure of the liquid within the tank increases and the tank s structural integrity is reduced because of the heating. If the tank ruptures, the hot liquid volatilizes explosively. 

The release of a flammable gas or the vaporization of a liquefied flammable gas can lead to different types of fire scenarios dependent on the release mechanism and the point of ignition. Figure 5-2 on page 53 illustrates the different outcomes expected from a gas release. If ignition of a gas release does not occur immediately at the origin of the release, then a gas cloud can develop (the same situation can also occur above flammable liquid spills). A delayed ignition of the gas cloud can result in a flash fire in which the premixed (fuel and air) gas cloud burns rapidly, typically in a matter of seconds. 

If one follows the solution viscosity in concentrated sulfuric acid with increasing polymer concentration, then one observes first a rise, afterwards, however, an abrupt decrease (about 5 to 15%, depending on the type of polymers and the experimental conditions). This transition is identical with the transformation of an optical isotropic to an optical anisotropic liquid crystalline solution with nematic behavior. Such solutions in the state of rest are weakly clouded and become opalescent when they are stirred they show birefringence, i.e., they depolarize linear polarized light. The two phases, formed at the critical concentration, can be separated by centrifugation to an isotropic and an anisotropic phase. A high amount of anisotropic phase is desirable for the fiber properties. This can be obtained by variation of the molecular weight, the solvent, the temperature, and the polymer concentration. 

Clouds, fogs, and rain, however, have much greater liquid water contents and thus have the potential for contributing more to atmospheric aqueous-phase oxidations. Clouds typically have liquid water contents of the order of 1 g m-3, with droplet diameters of the order of 5-50 yxm the number concentration and size distribution depend on the type of cloud. Fogs, on the... 

Vonnegut and Neubauer (24E), using liquids of low conductivity, have produced two types of droplet distributions by means of high voltage 5000 volts direct current produces a uniform stream of droplets of 100 micron diameter at the rate of about 100 per second. A cloud of fine particles which are so uniform in size that Tyndall spectra are apparent, is also produced. 

The reason for the dehydration and denitrification of the Antarctic stratosphere is the formation of the PSCs, whose chemistry perturbs the composition in the Antarctic stratosphere. Polar stratospheric clouds can be composed of small (< 1 pm diameter) particles rich in HNO3 or at lower temperatures (<190 K) larger (10 pm) mainly ice particles. These are often split into two categories, the so-called Type 1PSC, which contains the nitric acid either in the form of liquid ternary solutions with water and sulfuric acid or as solid hydrates of nitric acid, or Type II PSCs made of ice particles. The ice crystals on these clouds provide a surface for reactions such as... 

Pour point ranges from 213 K (-80°F) for some kerosene-type jet fuels to 319 K (115°F) for waxy No. 6 fuel oils. Cloud point (which is not measured on opaque fuels) is typically 3 to 8 K higher than pour point unless the pour has been depressed by additives. Typical petroleum fuels are practically newtonian liquids between the cloud point and the boiling point and at pressures below 6.9 MPa (1000 psia). 

Figure 7 also shows the influence of sea surface temperature, on 5p. Merlivat and Jouzel (1979), Johnsen et al. (1989), and Petit et al. (1991) show that source conditions (temperature and humidity) also influence the relative amounts of HDO and H2 0 in the parcel and thus the deuterium excess in precipitation. The model reproduces deuterium-excess values observed in Greenland (Johnsen et al., 1989) and in Antarctica, where d becomes higher than 15%o in central regions (Petit et al., 1991 Dahe et al, 1994). These results as well as those concerning the isotope-temperature relationship were further confirmed by Ciais and Jouzel (1994), who introduced mixed clouds into the Rayleigh-type model, thereby allowing supercooled liquid droplets and ice crystals to coexist between-15 °C... 

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