Telescopic Eyeglasses and Model Airplanes

detailsValley of the Kali GandakiThe valley of the Kali Gandaki features two superlatives:between Kalopani and Larjung one finds oneself standingat the bottom (approx. 2540 meters) of the world’s deepestvalley. Its winds display the most extreme diurnal cycleknown to scientists. The 8167-meter Dhaulagiri in the westand the 8091-meter Annapurna in the east are only about35 kilometers apart at this point. This means one is around5500 meters under the mountain peaks.At the breakthrough, the distance between the river bedand the peaks is more than 5000 meters. The Kali Gandakiis one of the four large rivers in Nepal. It rises in Mustangon the border with Tibet and flows into the Ganges.At Ghasa, the river rushes downward by a thousandmeters in a steep canyon and finally approaches Nepal’slowlands.The Kali Gandakiwind systemJoseph Egger and his team had setthemselves the goal of investigatingthe unusual wind system in theworld’s deepest valley together withthe model plane pilots WolfgangSchäper, Stephan Lämmlein and PhilipKolbe. While a wind with storm forceblows into the valley during the day,the wind leaving the valley at night isweak.Therefore, this wind system is totallydifferent from the wind systemsobserved in large Alpine valleys. Thequestion to be asked was how thisunusual wind system can develop inthe first place.By means of very successful measurementsand computer simulations,a conclusive explanation was finallyfound for the development mechanismof the Kali Gandaki winds. Awall separates the Mustang basinfrom the world in the south. A narrowpassage through the wall representsthe valley section from Ghasato Marpha. If the sun shines fromabove, the air in the basin heats upstrongly, and that in the foreland to alesser degree as there is much greatermass to be heated there. In the gateway,a valley wind then emerges, thespeed of which then increases. Thiswind extends into the posterior partof the basin. In the narrow connectingarea, the winds accelerate andreach the basin in the form of stronggusts.54In Practice Innovation 17, Carl Zeiss AG, 2006