These two pictures illustrate very effectively how mountain wave works. The Sierra's are built in a way that makes them excellent wave producers - a long gentle slope with a steep drop off on the back side. They need a westerly wind perpendicular to the ridge top to generate the wave, ideally with a unstable airmass on the bottom and a stable airmass with steadily increasing winds with altitude on the top. The lower unstable airmass acts like a spring for the air flowing over the ridge to bounce off, producing a standing wave.
For a better mental picture think of water flowing over a rock in a stream. There is always a standing wave on the downstream side of the rock. Mountain wave works the same way. The moving air over the mountain functions just like a fluid in motion, and the same fluid dynamics apply.
The record distance flight that you were describing was
a world record, flown in mountain wave, probably under an instrument flight plan flown entirely at the flight levels. Previous world distance records were flown in ridge lift and thermals down the Appalachian mountain chain from Pennsylvania to Tennesee (?) and back.
Recommended reading for sailplane and power pilots alike: Exploring The Monster
Excerpt from the Gliding Magazine book review - "Bob Whelan does a wonderful job of describing the thrills, and the life threatening hazards they faced, as they explored the unknown, at a time when most meteorologists just couldn't believe the stories they told. Most of the information was gathered from personal interviews with those involved. From Harland Ross soaring a Cessna 140 from 6,000 to 23,500', soaring a P-38 from 13,000 to 31,000', giving a power student an hour's lesson between 11,500 and 17,500' ALL with the engine off, tales of 'routine' turbulence of plus or minus 3g, to Bob Symons' "Do you want to set a world record today?", the meticulous preparation of the aircraft for flights in extreme conditions with temperatures frequently in the area of -70oC, and occasionally even lower in unheated cockpits, with the canopy inches deep in hoar frost on the inside, this is fascinating reading.
Any pilot considering flying in mountainous regions likely to produce lee waves would be well advised to read Larry Edgar's personal account of an encounter with a rotor cloud. The incredibly violent turbulence shook him to unconsciousness, leaving him temporarily blinded for 15 minutes, and falling with the rudder pedals wrapped round his feet, the rest of the aircraft having disintegrated around him after being subjected to forces calculated at -20 and +16g!"
Larry found himself going up
while hanging in his parachute! He worried that his bail out bottle would run out of oxygen until he drifted into the downside of the rotor and took a wild ride down. I remember reading his story somewhere years ago and saying to myself "Holy S**t!" while I was reading it.
As an interesting anecdote, my glider instructor and I once flew the Sierra wave at night in a Cessna 172. We parked ourselves in the wave, pulled the throttle back to idle, and climbed in the wave to 12,500' (ahem). We sat there in serene motionlessness for a little over an hour enjoying to nightime view of the Owens Valley before allowing the wind to push us back into the down side of the wave and landing back at California City airport.
The Carson Valley is also a world class thermal producer in the warmer months (as you've no doubt experienced). But it's very unique in that the thermals tend to be very strong, sometimes 1500 fpm, and sometimes quite large in diameter with broad areas of gentle sink in between. This isn't the rule, but the local terrain and weather conditions make it a very common occurence. Occasionally, the thermals go all the way to 15,000' and even higher, especially over the White Mountains of the eastern Owens Valley. You can run down the crest of the ridge under a cloud street at the gliders redline, traveling over a hundred miles without making a turn in a thermal.
Here in AZ, thermals also tend to be pretty strong but most of the time they're closer together with what can sometimes be very ferocious sink in between them.