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Edward E. Hindman

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Edward E. Hindman II

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A modified version of the Continuous Small Particle Sampler was used to obtain cloud particle samples of the phase change in a cloud chamber. The effects of silver iodide (AgI) and dry ice (CO2) were studied under similar conditions. Nucleation by AgI produced evidence which followed heterogeneous nucleation theory and crystal growth-rate observations. The dry ice seeding, plus a comparison with natural samples, illustrated Mason's homogeneous nucleation theory. Finally, total water content balances were computed and depict the water content of ice, liquid water content, and water vapor content proportions for each seeding.

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Edward E. Hindman

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Observations and measurements were made of supercooled liquid water in clouds which enveloped high elevation sites in the Colorado Rocky Mountains for the winters of 1980/81 through 1983/84. The observations showed that liquid water was more frequent at the southern and northern Rocky sites than at the central sites. Eighty percent of the liquid water periods persisted 3 to 20 h at the northern Rocky site. This site was enveloped by supercooled liquid cloud 24% of the time during the months of December 1981 and January 1982. Average liquid water contents at the sites ranged between 0.14 to 0.23 g m−3; the maximum individual value was 0.60 g m−3. The measurements indicated that substantial amounts of liquid water were flowing over the Colorado Rockies at mountaintop heights.

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Edward E. Hindman

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The cloud gun is a direct-impaction instrument for determining cloud droplet size distributions and number concentrations. The instrument was designed for airborne use. Procedures are detailed for operating the instrument at the surface. The Langmuir crater-to-diameter ratios are used for reducing the data. Liquid water contents from cloud-gun data collected at Storm Peak Laboratory (SPL), Steamboat Springs, Colorado are found to be similar to those reported from a replica cloud gun operated at Elk Mountain Observatory (EMO), 129 km to the north. This consistency in the SPL and EMO data is evidence that the procedures reported produce reliable results.

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Edward E. Hindman

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The flow of moisture through a “slab” of air, upwind and over the Park Range in northwest Colorado, was estimated from wintertime meteorological measurements. On average, 6–14% of the inflow moisture precipitated onto the barrier (86 to 94% flowed over the barrier). Because such a small amount of the moisture precipitates, snowfall augmentation activities on the upwind Park Range barrier should not significantly affect the moisture reaching the downwind Front Range barrier.

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Edward E. Hindman

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The formation of a warm cloud was studied in a 1.1 m−3, isothermal, slow–expansion cloud chamber. The evolution of the precloud haze droplet population into the incloud haze and cloud droplet populations was measured in unprecedented detail. The chamber environment was found to closely reproduce cloud formation in an adiabatically expanding parcel. Further, the microphysical characteristics of the cloud resembled those of a marine stratocumulus cloud. A procedure for estimating subsaturated and supersaturated relative humidity values was developed and shown to reproduce modeled values. Unique measurements of cloud droplets evaporating into haze droplets were obtained. The visual range within the chamber was calculated to he 4 m, a value sufficiently low to conduct electromagnetic energy propagation experiments.

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EDWARD E. HINDMAN II

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A sequence of aerial photographs is presented that illustrates the breakup of a stratus deck that filled the Redwood Creek Valley in northern California on Nov. 4, 1971. The vertical circulation within the valley was deduced from the breakup of the deck: air was rising along the sides of the valley, air was sinking along the center of the valley, and air was moving diagonally away from the center of the valley in a downstream direction connecting the rising and sinking air. This circulation has been suggested in theory, and the rising and diagonal components have been observed. The sinking component, however, has not been observed. The stratus breakup presented in this paper is submitted as evidence that the sinking component exists.

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Edward E. Hindman

A field course for undergraduate science students at The City College of New York (CCNY) is described. The students, who have completed an introductory meteorology course, conduct experiments at Storm Peak Laboratory (SPL) in the northern Colorado Rockies during winter breaks. The students apply their classroom learning to understand actual meteorological conditions. Prior to the field work, the students learn the necessary measurement and observation skills in a series of laboratories at CCNY and SPL. Experiments are conducted in both cloudy and clear conditions. From the clouds that envelop SPL, the students collect cloud droplets and snow crystals for physical and chemical analyses and for more detailed analyses at CCNY. For example, the students measure the pH of droplets as a function of droplet size and, in clear conditions, measure the diurnal behavior of valley temperature inversions. Following the winter field experiments, the students reduce and analyze their data during the spring semester. At the end of the semester, each student reports his or her findings in a scientific paper and presents the paper at a department seminar. Other university professors are encouraged to develop teaching and research activities at SPL.

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Edward E. Hindman II

Techniques have been developed for dissipation of supercooled fogs in the −4C to −20C range. However, no suitable methods have been devised to cover the 0C to −4C range. Nucleation theories associated with dry ice and reports from the literature are applied to three dissipation techniques: tethered balloon, ground blower, and aircraft seeding. These techniques are theoretically subjected to the same fog condition in the 0C to −4C temperature range. Resulting computations show that the aircraft technique is not operable in this fog case or the temperature range when using dry ice pellets. It was determined that the same mass of dry ice is needed for the dissipation of the fog in the remaining techniques. Computations associated with the dispersion of this mass into the fog are presented. A comparison of the dispersion operations show that the ground blower is the most feasible technique.

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Edward E. Hindman II and G. Garland Lala

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