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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 />. <br /> <br />20 <br /> <br />~ <br /> <br />Between the convergence zone over Pagosa and the SUMnit a circulation <br /> <br />pattern is formed in \vhich the air rises over the convergence zone and sub- <br /> <br />sides dmvn the side of the mountain. This circulation pattern \ViII be <br /> <br />referred to as a solenoid even though it is not known whether it is closed <br /> <br />or not at the top.. It is a closed circulation pattern if the downslope air <br /> <br />has its origin from ~ithin the convective cells. It is an open circulation <br /> <br />pattern if the dmmslope air has its origin from bet\>Jeen the convective <br /> <br />cells. The convergence zone becomes \>Jell defined and distinct \\Ihen the in- <br /> <br />stability is great. The convective elements over the convergence zone help <br /> <br />to drive the solenoid. If the solenoid was driven solely by the convection, <br /> <br />the convection would eventually transport all the solenoidal air up and over <br /> <br />the mountain. The result \\Iould be that the convergence zone would slowly <br /> <br />move to\Vard the mountain. It does not seem to move but rather remains <br /> <br />stationary. The fact that the solenoid remains stationary and is often <br /> <br />present prior to the development of convective instability suggests that <br /> <br />the solenoid is driven from both sides. This implies a process which cools <br /> <br />the air near the surface on the southwest side of the mountain near the <br /> <br />continental divide. Both evaporative cooling from sublimating sno\\I and <br /> <br />.conductive cooling from the cold mountain were considered to provide the <br /> <br />cooling mechanism. Insufficient data were present to determine which process <br /> <br />drove the downslope side of the solenoid. <br /> <br />Reed (1976) first noted a similar convergence zone upwind of the Climax <br /> <br />area. He observed the phenomenon in non-precipitating situations while <br /> <br />flying the NCAR Q/A over that area on a transport and diffusion study. <br /> <br />Mahyer and Pielke (1975) were able to numerically simulate a solenoid in <br /> <br />their X-Z, 2-D model by coo]jnr, the' up,,]ind mountaJn surface. In Nahycr and <br /> <br />Piclkc IS rdmuliJtion model the atmospheric l.:lpsC r3t:c was sl:i.ghtly stahle w.Lth <br />