What is the Mountain Wave?

In the Rockies, the Sierras, the Alps, and all other mountain ranges, there is a phenomenon that enables sailplanes to fly up into the stratosphere... This is the mountain wave. It happens on the DOWNWIND side of the mountain, when a strong wind blows across a mountain chain - but it can be also generated by mountain-size depressions, like the Grand Canyon. They are not limited to Earth: mountain waves have been observed on Mars. The illustrations show how it works:

The wind hits the mountain, and must rise. This is the slope lift. Then it drops down on the other side. When the atmosphere is "stable", the air bounces up again, and the whole atmosphere starts resonating, easily up into the stratosphere... Under the domes of the wave the air spins around in rotors. Areas of rising air are in green, sinking air is in red.	... and this is what it "really" looks like... Picture from a DG-505 from 15,800 ft (4800 m) by Andrea Marie Jaszlics on January 16, 2000. We are in the Wet Mountain Wave. 25 mi to the West, the Sangre de Cristo Primary and Secondary Wave, and the rotors are visible. The rotor clouds are the rough sausages, the wave clouds are the smooth ones above

What is it like? Before you get in the wave, you often must climb in the rotor. Sometimes this must be similar to the experience of a rat being caught in a clothes dryer - extremely turbulent. Other times the rotor is like a rough and unsteady thermal. Once you are in the wave - it is smooth! And you can move fast. In the picture above to the right, we were indicating 112 Knots. At a density altitude of 5500 m this is 149 KTAS, or 172 mph (277 km/hr). We were doing this in straight, still gently climbing flight, covering a 30-mile run in about 11 minutes! And it was smooth as glass!