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<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 />II <br /> <br />28 <br /> <br />and in the 'convective elements \vere small, as expected. HO\,'ever, the spectra <br /> <br />over the mountain frequently contained large droplets; in one case, a majority <br /> <br />of the droplets had diameters in excess of 20 pm. The droplet spectrum is of <br /> <br />some interest in considering the problem of ice multiplication, since one <br /> <br />propqsed mechanism (Hallett and Mossop, 1974) requires the presence of large <br /> <br />droplets. The droplet sizes are also important in considering the accretional <br /> <br />contribution to the precipitation process, since the large droplets have in- <br /> <br />creased riming efficiency. <br /> <br />Droplets larger than 20 ~m diameter were found only in the region over <br /> <br />the mountains. The liquid water here was rather long-lived, and apparently <br /> <br />\vas produced by continuous lifting over 15-20 km, or typically 15-20 minutes. <br /> <br />This region \<las al\vays located at cold temperatures, and therefore \'laS not a <br /> <br />candidate for the Hallett-Mossop multiplication mechanism. No region was <br /> <br />observed in these storms \,1here both the droplet spectrum and the temperature <br /> <br />met the requirements of the Hallett-Mossop mechanism. <br /> <br />The bimodal droplet spectra occasionally observed over the mountain <br /> <br />(see V.A.3.e) suggest a dual origin for the droplets in this region. A <br /> <br />possible sequence would be for convection to form the initial droplets, and <br /> <br />then for the convective elements to merge with the general upward motion of <br /> <br />the air over the mountain so that a second supersaturation peak occurs. If <br /> <br />the general updrafts moving over the mountain are increasing, and reach a <br /> <br />maximum greater than the updraft in the initial convective cell, a bimodal <br /> <br />spectrum could result. <br /> <br />In summary, the liquid \.Jater observations indicate considerably less <br /> <br />extensive liquid water regions than were anticipated. However, there are <br /> <br />still significant liquid regions which are important to the precipitation <br /> <br />process and ~lich may be secdable. The extensive liquid water region over <br />