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<br />as with the transport and dispersion studies; (2) aircraft 1 ine <br />releases of AgI across the prevailing winds; and (3) vertical curtains <br />of dry ice (C02) caused crystals, also across the prevailing wind. <br /> <br />For seeding in (2) the instrumented aircraft would be equipped <br />with one AgI generator. TIle dry ice seeding for (3) would utilize <br />manual dispersion from a small aircraft. For sampling, in the <br />first case (ground release of AgI), flight passes would be made <br />across the wind (AgI plume) at various downwind distances at <br />various altitudes. In the other cases (airborne release), sequen- <br />t i al passes woul d be made along the wi nd as the 1 i ne or vertical <br />curtain moves across Grand Mesa. In all cases, it would be <br />attempted to identify the seeded portion of the cloud and compare <br />it with neighboring non-seeded portions. <br /> <br />Aircraft measurements required in these experiments would be: <br /> <br />a. Ice nucleus concentration <br />b. Ice particle concentration, size spectra, and habit <br />c. Liquid water content <br />d. Temperature <br />e. Oewpoint temperature <br />f. Horizontal wind velocity <br /> <br />Precipitation would be measured with several high resolution <br />gauges atop Grand Mesa to obtain ground observations in the zone <br />where the seeding-induced snowfall should reach the surface. In <br />addition, the microwave radiometer and Rosemount icing probe would <br />be operated at the observatory. The radiometer should respond to <br />seeding-induced changes as the seeded cloud volume moves above it; <br />thus, even if seeding-caused ice particles do not reach the sur- <br />face at the ohservatory. evidence of them may be apparent in the <br />radiometer record. The target area would be limited in extent, <br />generally to the area within a few miles of the observatory <br />because most sensors are located in that zone. <br /> <br />c. No Action Alternative <br /> <br />Under this alternative, no seeding activities contributing to the <br />Bureau's atmospheric water resources program would take place in the <br />Upper Colorado River Basin. Research into physical processes of <br />storms, development of new instrumentation appl ications, testing <br />techniques, and methods of evaluation of results would be curtailed. <br /> <br />. <br /> <br />Present climatological research has reached another stage in the need <br />for data. The climatological data base needs to be related to <br />seeding effects. Climatological studies would continue, but without <br />this next logical step in the process they would be of much more <br />limited benefit. <br /> <br />13 <br />