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Wallace E. Howell

VOL. 17, NO. 12 JO'URNAL OF APPLIED METEOROLOGY DECEMBER 1978Night Versus Day Cloud Seeding in Langmuir's Periodic Experiment WALLACE E. HOWELLOffce of Atmospheric Resources Management, Division of Research, Bureau of Reclamation, U.S. Department of the Interior, Denver, CO 80225 (Manuscript received 8 December 1977, in final form 10 June 1978)ABSTRACT During the last ten 28-day cycles of

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Donald A. Haines

twocounterrotating HRV's having sustained upwardmotion. Bagnold (1952) suggested that long parallelsystems of sand dunes, covering more than half ofthe world's deserts, are aligned and spaced by thisatmospheric mechanism. Hanna (1969) offered further observational evidence and outlined a model insupport of this hypothesis. Ocean and lake observations by Scott et al. (1969)and otlhers show at least two types of water mechanisms referred to as Langmuir circulations. Type1 produces well-defined and well

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Steven R. Hanna

-p'ing (1963) has observed longitudinaldunes aligned with the prevailing wind and havingspacings of -'-0.3-2 km.The largest mountain-valley circulation in the worldmay be observed in the huge Takla-Makan basin inCentral Asia, according to Fedorivich (1948). Nearlysurrounded by high mountains, this desert heats upduring the daytime and acts as the center of a largeconvection cell. During the night cold air drainage fromthe mountains occurs. As a result of the convergence ofwinds, the dunes all appear to be

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Robert T. Ryan

free fall has been examined. To study theterminal velocity, shape, evaporation, circulation andbreakup of raindrop-sized water drops, investigatorshave used a variety of vertical wind tunnels and droptowers or drop tubes (Lenard, 1904; Schmidt, 1909;Flower, 1928; Laws, 1941; Blanchard, 1949; Gunn andKinzer, 1949; Fournier d'Able and Hidayetulla, 1955;Magarvey and Taylor, 1956; Komabayasi et al., 1964;Cotton and Gokhale, 1967; Pruppacher and Beard,1970). However, of all the studies, only a few

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Gregory J. Tripoli and William R. Cotton

data as a basic state. The initial magnitude and distribution of low-level convergence was varied and the sensitivity of the n~odel to some microphysical parameters was examined. The results of the numerical experiments show that (i) the magnitude of surface convergence over afinite area has a pronounced influence on the simulated storm circulation, the eddy kinetic energy of thestorm and the total rainfall of the Storm system; (ii) the horizontal distribution of convergence has arelatively

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Stewart G. Cober, J. Walter Strapp, and George A. Isaac

. Introduction The concept of drizzle growth by a combination ofcondensation and collision-coalescence has long beenrecognized in cloud environments where the temperature is warmer than 0-C (see, .e.g., Langmuir 1948;Ludlum 1951). Pruppacher and Klett (1978) gives ahistorical overview of work in this area, while Beardand Ochs (1993) provides a more current review. Thisphenomenon has also been inferred in several studiesfor clouds in which the temperature of the cloud environment was colder than 0-C. The

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Vernon G. Plank and Alfred A. Spatola

, moreover, that the entrainmentamounts into the jet should increase directly with thestability. If the computed downwash temperatures at largestability are excessive, it follows that the diagramindicated velocities and penetration distances are alsotoo large. By how much, however, is unknown. The Hohler equations provide no information aboutthe radial (horizontal) components of wake motion, orof the general wake circulations in regions outside theimmediate downflow zone. We might speculate

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Edwin X. Berry and Maarten R. Pranger

Reynolds number, the physical basis for extrapolations ofthese equations far outside the limits of the data isweak. Internal circulations, mechanical pulsations, andirregular vortex shedding combine to make the fallvelocity of large drops somewhat irregular (Dingle andLee, 1972) and certainly difficult to calculate.5. Conclusion The curve-fits given here provide a very close fit toexperimental data at sea level. The use of Re as a function of CdRe2 for the curve-fits provides a physicalbasis for

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R. J. Pilié, E. J. Mack, W. C. Kocmond, W. J. Eadie, and C. W. Rogers

of error in these measurements are statistical innature, imposed by the time required t? measure largernumbers of replicas for each distribution. These errorsare particularly important for small droplet size~(<3/~m radius) where the number of replicateddroplets is limited by small collection efficiencies and,consequently, collection efficiency corrections are large(Langmuir and Blodgett, 1946). Similar problems occurfor large drop sizes where natural concentrations aresmall. A second type of

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Jindra Goodman

corrections(Langmuir and Blodgett, 1946). For the larger dropletsthe errors arise due to the small sampling volume.Droplet samples were taken every 60-90 min at severallevels to obtain the variation with time of the sizedistribution in the vertical.The drop size distribution was found to be a functionof vertical distance from the inversion base. Typically,the mean and median diameter increased with height,as shown in Figs. 4-6. The selected microscopic photo-graphs taken on 27 July 1974 (Fig. 7) further

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