Tropopause Ii, The Return of the Yeti Options

[Fast Jet]

Ok, where we at. . . ?

Over the Pole at 90*N-you have the Arctic Tropopause at just over 5 kilometers (km) high. you have to convert km to feet.

((3.281 ft per metere?)) (4km x 1000 = 4000 x 3.281 = 13,000 feet) So, Shauna takes the entire Flight Level 350 Cookie Jar for the year!!

Further south at 70*N the is the Arctic Front and the Polar Tropopause here starts at around 4 km high or less ! ! So, you are more than right. If you are at school, tell your teacher to give you a gold star or a credit, recommended by the Royal Aeronautical Society.

But, sorreeeee, I have never seen a tropopause so low before, even though it is in the books, strangely, they always seem to be in the low twenties like: FL200, FL220 etc. . . . I don`t why there is this anomoly, maybe someone else can dive in and comment. In short, I would be surprised, but only because I have not seen one so low as FL130
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Also, unrelated to your point about the Tropo when the ground temp is -30 . .

The warm(er) tropical air rises high and over colder air. At that point the tropical air tumbles over the polar air, its rising over its over lapping, its also going from high pressure to low which what gives it its motion, momentum, as it tumbles, rolls over the top of the colder polar air it rotates like the rotor cloud at the lee-side of a mountain range (just for description ok?) it revolves and this rotates and the centre of this rotating long roll of air becomes the jetstream which because of the pressure gradient moves from high press to lo press.

You now have a river of a high wind going (rotating) going from high press to lo press and in invariably westerly (from the West) has flattened out, for some reason and is now a river of wind about 500 or 600 feet thick, or more and about 100 to 250 nautical miles wide flowing across the Atlantic or any other area wherwe there are jetstreams. They have them in the Pacific too, and although westerly, the cheeky baskits turn 180 degrees often over the Rockies and become Easterly Jets - so your lovely Ground speed of 500 knots on your way to Calif is now 340kts after a big bump too!

The (polarside) edge is still rotating throughout its short life (of a few hours) so if your aeroplane gets on the polar side of it then you will get real bad clear air turb (CAT) as the wind (in the over lap remember?)
is rotating - to avoid this just fly to the south of the jet off-set your track and to a lower flightlevel to keep away from the polar "core" of the jet(stream)

The well made charts of today - SiG Wx charts from NOAA and the FAA etc., show you the position and track of today`s jetstream and also gives you the recommended 80kt levels to fly (above and below the jet) so as you can have a nice 80knot wind and avoid the core of the jet and the CAT.

There is a fantastic book on this subject by Roger G. Barry and Richard J. Chorley called Atmosphere, Weather and Climate. (Eighth Edition)

And just for interest, we had three (3) jetstreams today overhead - at about 290 / 310 / 410 (on average) and consequently it has been VERY, very windy on the ground.

Check it out - its a hit!

http://aviationweather.gov/products/swh/

5 feb 11 UTC