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<br />These weather conditions, although typical for the area during <br />wintertime, were only observed five or six times during special <br />field program dates. In addition, some field measurements were <br />made during southwest (270-1800) airflow situations. <br />3. Special field programs <br />The primary objective of the special field programs were <br />to collect sufficient imformation to check on the laboratory <br />results. The programs were not large scale and therefore their <br />objectives were quite limited. On occasion the field programs <br />of the study benefited from other active programs in the same <br />area such as the National Science Foundation's Rocky Mountain <br />orographic cloud precipitation and modification program and the <br />State of Colorado weather modification program. <br />The principal objectives of the field program were as <br />follows: <br />a) Obtain sufficient radiosonde, pilot balloon (rawin) and <br />near surface data to define the vertical structure of the <br />atmosphere in orographic terrain, especially during weather <br />conditions when cloud seeding would most likely be in operation. <br />b) Obtain data on the trajectory of air parcels, by means of <br />the superpressure balloon technique and also make estimates <br />on the atmospheric dispersion from these same measurements. <br />c) Obtain surface samples of tracer material (e.g., si1ver- <br />iodide, zinc sulfide, sulfur hexaf10ride) downwind from <br />generator sites in order to determine the dimensions of the <br />tracer plume. <br />d) Obtain upper-level samples of particulate material using <br />a kite system and aircraft. Primary emphasis was on obtaining <br />measurements on the vertical depth of the tracer plume by <br />using an aircraft as a sampling platform. <br />Seven periods of field data collection were implemented <br />to attain the four objectives listed above (Table 3-1). During <br />these periods, especially those for 1969-70, the following tasks <br />were at least partially completed: <br />a) Collection of radio-and rawin-sonde data at Minturn (upwind), <br />Camp Hale (upwind, near the Ridge), and Fairp1ay (downwind). <br />b) Collection of pilot balloon data taken at four different <br />locations from Minturn to Chalk Mountain. However, low cloud <br />ceilings limited the vertical extent of the data. <br />c) Realization of dual and single super-pressure balloon <br />runs in the Camp Hale, Leadville and Redcliff areas. Eight <br />of the balloon releases were tracked by a double-theodolite <br />technique and six releases were tracked by a M-33 radar and <br />transponder system. 8ix of the eight releases tracked by the <br />double theodolite technique were done under general northwest <br />wind conditions and have provided additional data on the local <br />dispersion characteristics in the Camp Hale area. <br />d Sampling of silver-iodide tracer material near the surface <br />was accomplished at Chalk Mountain and Tennessee Pass. <br />e Seven aircraft sampling flights were completed in the <br />Climax-Leadville and Eagle River Valley area. Four of the <br />flights were made in weather conditions comparable to conditions <br /> <br />~ <br /> <br />" <br /> <br />26 <br />