Cloud base height

The network of 211 weather stations allows measurement of tens of basic weather parameters, the most important of which include air temperature, atmospheric pressure, air humidity, wind speed and wind direction. Among the other parameters measured are cloud base height (laser-measured), amount of precipitation (rain or snow), visibility, and air temperature near the ground. Measurements are performed in enclosed areas within the weather stations. 

The air-mass thunderstorm is the least severe of all thunderstorms. In its simplest form, an air-mass thunderstorm grows as a single cell when solar radiation heats the surface air in an unstable atmosphere. Its life cycle lasts around 30 minutes. Towering cumulus clouds are formed as in-cloud updrafts push moisture upward. The tower may reach a height about five times the diameter of the cloud base in the growth phase. 

West Africa was three days, which they found to be similar to the mean residence time of gaseous inorganic chlorine of 2.25 days. The lifetime of gaseous inorganic bromine, however, was —7.25 days. Moyers and Duce (1972) estimated that the lifetime of gaseous bromine would be —7 times that of particulate bromine. These numbers are of course dependent on transport and deposition which vary with time and location. The vertical profile of sea salt aerosol was examined by Woodcock (1953) and Blanchard and Woodcock (1980), who found an exponential decrease with height and a salt inversion (i.e., local maximum) near cloud base. 

Let us suppose that the radius of raindrops is uniform and equal to R. One raindrop obviously sweeps out an air volume of R2nh between the cloud base and the surface if the height of the cloud base is h. Let this air volume be filled with a monodisperse aerosol containing particles of unit density with radius r at a number concentration N(r). Then the total mass of aerosol particles in the air volume swept out will be ... 

B. FM 3-3-1 details the steps needed to determine the yield from cloud parameters. The M4A1 nuclear yield calculator is designed to provide rapid yield estimation based on any parameter except cloud-top or cloud-bottom height. Refer to the equipment chapter in this Battlebook for additional detail. 

It increases with height above the cloud base, reaches a maximum value somewhere in the upper half of the cloud, and then decreases toward the cloud top. 

Figure 15.31 shows a zonally averaged climatology based on six cloud types high clouds (Ci, Cs), middle clouds (As, Ac), low clouds (St, Sc), cumulus, cumulonimbus, and nimbostratus. The altitude, thickness, and cloud cover are shown with a 10° resolution. Note that the cirrus base heights vary with latitude but their thickness is fixed at 1.7 km due to limitations of the observations. 

FIGURE 1 Temperature vs height distributions. Solid line, in a rising parcei of air AB, beiow cioud base, dry adiabatic BD, cloud base to cioud top, entrained ascent. Dotted line BC, moist adiabatic. Dashed iine environmentai temperatures. 

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 lower boundary condition, u(zo), is the zonal wind speed at level zo- Elson (1979) has applied this diagnostic relation to the temperatures shown in Fig. 9.2.10. The lower boundary was taken to be at the cloud top height, zo = 65 km, and the wind speed, u(zo), was based on observed cloud motion. The resulting cyclostrophic component of the zonal wind in the northern hemisphere is shown in Fig. 9.2.11 as a function of latitude and z. At levels above the zero contour line pure cyclostrophic balance cannot hold since 94>/90 becomes positive. Other terms in Eq. (9.2.21) then become important in this part of the atmosphere. This result has led to the application of more complex diagnostic models by Taylor et al. (1980). 

Numerous analyses of data routinely collected in the United States have been performed by the U.S. National Climatic Center, results of these analyses are available at reasonable cost. The joint frequency of Pasquill stability class, wind direction class (primarily to 16 compass points), and wind speed class (in six classes) has been determined for various periods of record for over 200 observation stations in the United States from either hourly or 3-hourly data. A computer program called STAR (STability ARray) estimates the Pasquill class from the elevation of the sun (approximated from the hour and time of year), wind speed, cloud cover, and ceiling height. STAR output for seasons and the entire period of record can be obtained from the Center. Table 21-2 is similar in format to the standard output. This table gives the frequencies for D stability, based on a total of 100 for all stabilities. 

Atmospheric Transport Processes. If an atmospheric constituent is not removed, then it will be transported by the winds, which vary greatly in time and space. The vertical dimension is particularly important, not only because transport speeds increase with height but because the probability of encountering clouds increases with height and the likelihood of being trapped by a ground-based... 

There is sufficient H202 in clouds to oxidize the S02 which reaches cloud height and calculations estimate that the multiphase oxidation of S02 by H2O2 accounts for most of the sulfuric acid present in rain, and over 70% of the sulfate aerosol observed in the atmosphere [79]. The aerosol is produced after evaporation of cloud droplets. It has been found in experiments carried out in the real atmosphere that the overall rate of oxidation of S02 in clouds is many times faster than would be predicted from using laboratory-based measurements [80]. 

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