What drives the Jets stream?

[[1ponders]]

This is just a general question to help those new to this maddening phenomenon get a better handle on why amateur astronomer curse it.

What drives the Jetstream? Over the past few weeks it seems to be just sitting over the southern parts of SE Qld travelling at between 160 and 220 mph. :mad2: Why hasn't it moved north/south or the worst of it east/west.:mad2:

[ballaratdragons]

Jet Fuel :shrug:

[sheeny]

Yeah, good one Ken!:lol: I was gunna say the pilot stream...:P

Al.

[ballaratdragons]

But that would be spamming Pauls thread! :whistle:

[sheeny]

It would. And I wasn't going to... but you started it!:D

Getting back on topic... I've forgotten what the jet stream looks like...



clouds, clouds, clouds...:sadeyes:

Al.

[Harpspitfire]

i think my telescope- LOL

[ballaratdragons]

Paul,

The jet streams (there is more than one) are caused by temperature differences in the atmosphere.

The most famous jet stream is the Polar Jet Stream. It forms where the cold, polar air meets the warm air from the tropics. The large temperature difference between these two causes a large pressure difference as well.

Air from high pressure flows in the direction of low pressure. Since the pressure changes so quickly, the air flows between pressures very fast. The strong winds are formed, which are called jet streams.

Or for the long answer:
http://www.atmos.millersville.edu/~lead/JS_Advanced_Answers.html

[CoombellKid]

No actually it's the speed of the All Black backline : )))

regards,CS

[sheeny]

I'll bet there's a Coriolis component in there somewhere too!;)

Al.

[acropolite]

My understanding is that it is also related to the earths rotation. It's interesting that we were blissfully unaware of the jetstream until WW2 when high altitude bombers discovered that their ground speed at high altitude was not as anticipated.

[IanL]

Jet Streams

At high levels of the atmosphere, strong winds develop as a result of the pressure difference, these winds known as the jet streams are usually located at about 30,000 to 35,000 feet (9000 to 10,000m) and their speed can be as much as 180mph (300kph)
Jet streams can strengthen and steer low pressure systems during winter, when there are greater temperature contrasts, the jets are more pronounced and shift towards the equator. In summer when temperatures are more uniform the jets tend to weaken and shift pole ward. Roll on summer.

Taken from my book on weather

[[1ponders]]

I think your book might need an update Ian :P According to the weather map (http://weather.wvec.com/auto/wvec/global/Region/AU/2xJetStream.html)over the past few weeks we've been experiencing 220+ mph at times with the average at around 160-180 :eyepop: . It has been a right pitb.

Welcome to SE Qld, beautiful one day, 200 mph Jetstream the next :doh:

[GTB_an_Owl]

so i take it that us uninformed newbies when looking at the jetstream maps are looking for the LOWER speed colors ? - or none at all

geoff

[[1ponders]]

If it's yellow Geoff, do youself a favour and image in widefield. Nice and clear with very short arrows is what you want for planetary imaging.

[GTB_an_Owl]

i haven't gone over to the dark side yet Paul

strictly visual here

geoff

[IanL]

Paul i am not complaining. When i stayed in Glasgow i was lucky to get out 2 nights a month because of clouds and rain. When i moved to Brisbane i was amazed at the amount of clear nights. :thumbsup:

[Don Pensack]

The air at the equator is headed east with the Earth at 1000mph. As the tropical sun heats the air, it rises, and cooler air from both north and south roll in to fill the void. the air filling the void is rotating with the Earth slower than the air it replaces, so it heads West at a slow speed.
The hot air that has risen heads north and south, and falls to earth moving east substantially faster than the surface of the earth. These are the constant easterly tradewinds.
This process repeats itself with belts of warm and cool air all the way to the poles, though the wind speeds become smaller there.
In the temperate belts, the air temperature isn't as great a differential, so the belts get wider, and the differential speeds of the airstreams even higher. Though water, land obstructions, and other topographic features keep the bands from being colinear with latitude, the speed of the air travelling north and south results in a band of high velocity wind headed east at temperate latitudes. This band drops toward the equator during winter and travels away from the equator during summer. During the reversal of seasons, the jetstream can be remarkably "fixed", but, inevitably, it begins to move toward the equator once again.
This high altitude movement, combined with an understanding of the air movement underneath it, explains why surface winds can often travel in the opposite direction from those aloft.
For me, at 34 degrees N, the surface winds often blow from east to west when the upper atmosphere is moving the opposite direction.
To research this further, look up "Coriolis Effect", "Jet Stream" "Atmospheric bands" or "atmospheric movement".
Don