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<br />" . <br /> <br />- 80 - <br /> <br />and, <br /> <br />x(t + ~t) = x(t) + u~t <br /> <br />(3.9l) <br /> <br />For larger particles E # 0, and eqns. (3.e7) and (3.8S) are simultaneously <br />numerically inte~rated from t to (t + ~t) to yield r(t + 6~) and z{t + ~t) <br />assuming E = l. Eqn. (3.91) is used to evaluate x(t + ~t). <br />3.5 Some results from the Theoretical t10del <br />In practise results are obtained from the theoretical model in the <br />following manner. The airflow model (93.2) is first run using an upwind <br />"","md; nr-; of temperature and winds and the results (i. e. streamlines) are <br />stored on tape. Subsequently, any number of ice particle trajectories can <br />be determined using either postulated or measured ice crystal concentrations <br />(N ). <br />o <br />Three sample outputs are shown in Figs. 3.5, 3.6, and 3.7. The airflows <br />used to obtain these results correspond to Figs. 3.3, 3.2, and 3.4, <br />respectively (see ~3.2.4). The wind and temperature profiles in Fig. 3.1 <br />co,t.,t'ei:lpond to the horizontal position x = -40 km. Figs. 3.5 and 3.6 show <br />calculations for a west wind, while Fig. 3.7 is for a southwest wind. There is <br />a marked difference in the terrain profile that is presented to the wind in <br />these two cases but most of the difference is downwind of the target area. In <br />both cases the target is the zero of the horizontal scale (x = 0). The water <br />shed divide is the rise of land immediately upwind of the target. When the <br />wind blows from the west the terrain downwind of the target area falls away <br /> <br />I <br />I <br />I <br />1 <br />I <br />I. <br />t <br />l <br />,I. <br />I. <br />I <br />I- <br />I <br />I <br />I <br />I <br />I <br />I <br />I <br />