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<br />xvi <br /> <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 />I <br />I <br />I <br />I <br />I <br />I <br /> <br />and seeded precipitation, However, the model fixes did not entirely <br />eliminate the low-level warm bias. <br />. The best 30 cloud-seeding days were selected for use in post-season <br />research evaluations, When compared to measured 24-hr precipitation at <br />61 SNOTEL sites the model exhibited a mean precipitation bias of 11.88, <br />The highest bias areas included the Target Area. The lowest bias areas <br />were in more upwind areas in northwesterly and southwesterly events, <br />Possible sources of those biases are discussed in the text and are <br />currently still under investigation. <br />. The model control simulations produced a reasonable qualitative pattern <br />of total precipitation and its topographic dependence for the 30 selected <br />days, The 30-day simulated precipitation total showed only light <br />precipitation over the entire SE leg and south half of the SW leg of the <br />target area, Thus the model suggests little orographic precipitation <br />potential and perhaps little cloud seeding potential over the two south legs <br />of the target area. <br />. The model forecast precipitation data were evaluated against SNOlrEL <br />data using MRBP statistical analysis procedures. The results from the <br />evaluation show that the model is describing the non-seeded and sl~eded <br />simulation equally well. While the signal of the fits is strong (all P-values <br />about 1.0E-6 or less), the agreement measures are not outstanding (all fall <br />between 0.18 and 0,26). <br />. Comparison of model-predicted precipitation (control) versus seeded <br />precipitation revealed that there was essentially no difference between the <br />86-day seed and control average totals (difference of -1.0 mm) or the 30 <br />days selected for model precipitation evaluation seed and control average <br />totals (difference of -0.2 mm), <br />. Langrangian trajectory analyses of six selected days of the subset of 30 <br />days selected for precipitation evaluation revealed that particles are! <br />generally being transported to the target area by the targeting wind as <br />intended, On average, 54% of those particles are 50-500 m AGL, with <br />another 34% in the layer 500-1000 m AGL, which are levels suitabll~ for <br />Agl seeding, <br />. The Lagrangian analyses confirm that generators should not be used <br />when the targeting wind would not carry their plumes over the targe,t area, <br />Low level trapping of particles can become moderate in nocturnal <br />inversions, but significant numbers of particles escape the inversions and <br />are transported by the targeting wind as intended, It appears that <br />generators located on the lee side of mountain ranges may be in <br />stagnation zones or rotors associated with high amplitude mountain <br />waves, and their particles are also subject to moderate local trapping, <br /> <br />The very small differences between seed and control precipitation predictEld by <br />the model were very disappointing and not expected at the onset of this project. <br />Possible causes of such low seedability: <br />