OCR Text |
Show Comparison of Collected Precipitation and Support Data with Computed Time and Location of Seeding Effect 4. 5. 1. 4 Data collected over the experiment area network included: Optical snow-rate sensor continuous records (with 5-minute resolution under optimum conditions). (1) (2) Modified weighing bucket snow gauge records O 968-6 9 time resolution F::1 15 minutes under optimum conditions and 1 hour in previous years). (3) Snow samples collected on plastic sheets over various time periods (optimally over 15 minute intervals) and analyzed for silver content. ~/ m (4) Snow crystal replicas made at 5 to 30 minute intervals and analyze: for crystal type, size, rimin g , and AgI particles serving as crystal nuclei. N ! (5) Continuous recording of ice nucleus concentration during operational periods. w N (6) Continuous vertical pointing radar AGC voltage records from the Lodwick site (which can be converted to z value). (7) PPI radar photos from the Mt. Harris facility. Inter-comparisons of time histories of all these data were made, as well as comparisons of the indi victual records to the computed time and location of occurrence of seeding effect- Of particular importance was the four way comparison between ( 1) computed time and locations of seeding effect, (2) optical snow-rate sensor records, (3) silver-~n-precipitation concentration (obtained by AAS analysis of collected snow samples), and (4) the percentage of individual snow crystal replicas (on each replica slide) growing microscopically visible AgI crystals at their centers. The time, elevation, and intensity changes of maximum AGC voltage from the vertical pointing radar at Lodwick (in the western edge of the target areal, when compared with computed passage time and vertical position of the seed· ~1 0 ing effect, and with the elevation of the -15 °C isotherm at times yielded im· portant information concerning the sign of the seeding effect. PPI photos were used primarily to check for (1) the passage of convective bands, and (2) the existence and slow southward migration of an east -west convergence band of precipitation which frequently exists over the area under conditions of northwest flow aloft (for details of this phenomenon, see 3. 3), 148 |