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<br />II <br />II <br />II <br />II <br />II <br />II <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br /> <br />4.0 DATA REDUCTION & ANALYSIS <br /> <br />The data analysis phase of this project primarily involved <br />data collected during the Experimental Period for selected Case <br />Study days (a list of Case Study days is given in Section 3.3). Only <br />a cursury analysis was made of the Operational missions. In order <br />to prevent bias, the radar, voice, computer, and film data were <br />reduced by contractor personnel without knowledge of which days <br />were seeded with placebos or live AgI flares. Thus data reduction <br />was the first in a series of contractor tasks in support of the seed- <br />ing evaluation. <br /> <br />4. 1 Area of Effect Computations <br />The first step in the analysis task was t6 compute <br />"plumes" which we defined as a best estimate of the area of effect. <br />Determination of the plume required an evaluation of PPI overlays, <br />seeding locations, winds at several levels through the cloud region <br />and the dispersion characteristics of the seeding material within <br />the atmosphere. The following steps were used in estimating the <br />area of effect: <br />1. From seeding altitude, determine the mean wind <br />wind speed and direction for the cloud layer. <br />2. Using seeding delivery locations, project the <br />downwind movement based on the mean wind. Allow the <br />seeding material to disperse (spread) using a 22 0 arc (11 0 <br />either side of center line). <br />3. Modify the initial plume estimate taking into <br />account, (a) variation of wind with altitude (direction shear), <br />(b) movement of echoes as determined by the PPIoverlays. <br />4. Use a time interval of 25 minutes for the initial <br />fallout delay; and from there, project a downwind mov,ement <br />of two hours. <br /> <br />34 <br />