Jet Streams

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frosty

Member
What influences jet streams to buckle into a trough, or rise into a ridge?

Also does jet streams influence high and low pressure circulations or is it pressure circulation that influence the jet streams?

How many jet strems are there that run across the US and whats their typical speed?

My kids and I were watching the weather last night and they started asking me these questions. I told them I had to get back to them. I would appreciate any info.
 
jd

jd

Administrator
Staff member
It gets pretty technical to try and describe all that makes the jetstream do what it does, but the main driving force behind the jetstream is temperature difference. Also think of the ridges and troughs in the jet as waves. However, instead of them crashing to shore, they just keep on traveling around the globe. Things like strong temperature differences then cause the waves to grow larger.

The jet is responsible for influencing weather here at the surface like high and low pressure systems.

There can be up to 3 different jetstreams over the US at one time; the sub-tropical, the polar and the arctic. However, this is only really possible in the winter as the arctic retreats way up into the arctic regions and then dissipates over the summer and the sub-tropical jet also disappears in the summer, leaving a very weakened polar jet to be the lone jet out there.

Speeds will vary from 50-70 mph to over 200 mph. The strongest jetstreams occur in the winter.

-John
 
F

frosty

Member
With the jet stream being like a wave that never crashes, how does a severe trough staighten out. For example, the huge buckle that not once but three times that slammed the north east on three different occasions. How did the jet stream straighten out when it made the circle back around to the west coast. Was there that much of a temperature difference in the Atlantic to Europe to straighten it out or did the Rockies do that?
 
jd

jd

Administrator
Staff member
The troughs and ridges propagate around the hemispheres and also the same things that cause them to deepen cause them to flatten out- only in an opposite manner.

The jet does not stay flat too long though- especially in the winter.

-John
 
F

frnash

Active member
frosty said:
Why do jet streams run west to east when the rotation of the earth is east to west?
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'Cuz the air mass is stationary, and the earth moves beneath it (spinning on its axis), making it appear as though the air mass "moves" from west to east! :)

Of course the air mass is "dragged along" by surface friction with the earth to some degree, and there are also differing atmospheric pressures in different segments of the air mass, plus temperature differences, both of which influence air flow (i.e.winds) resulting in quite complex variations in the atmospheric motion.

Not exactly a "scientific explanation", but I'll betcha I'm kinda close!
 
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F

frosty

Member
I see says the blind man. I thought the earth rotated clockwise, not counter clockwise. Now it makes sense, not! :p

So the air is still not moving, or is it moving? :confused:
 
F

frnash

Active member
frosty said:
I see says the blind man. I thought the earth rotated clockwise, not counter clockwise. Now it makes sense, not! :p
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Clockwise or counterclockwise depends on where you're standing. If you are standing at the north pole, the earth would be turning counterclockwise; if you are standing at the south pole, the earth would be turning clockwise!

Since the sun appears to "rise" in the east, and "set" in the west, it is in fact the earth rotating eastward around its axis, as shown in the image provided by rjgoniea.

frosty said:
So the air is still not moving, or is it moving? :confused:
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The air mass is indeed moving, generally with the rotation of the earth as it is "dragged along" by surface friction, and in other complex motions due to the atmospheric pressure and temperature differences, both of which influence air flow (i.e.winds).
 
F

frosty

Member
Okay, now explain this to me. The earths rotation is spinning at like thousands miles per hour. Why isn't the air mass moving thousands of miles per hour, or is it and the wind now is rotation of the earth plus whatever the air speed is?:D
 
F

frnash

Active member
frosty said:
Okay, now explain this to me. The earths rotation is spinning at like thousands miles per hour. Why isn't the air mass moving thousands of miles per hour, or is it and the wind now is rotation of the earth plus whatever the air speed is?:D
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The circumference of the earth at the equator is approximately 24,000 miles (closer to 24,902 miles, in fact), so a point on the equator would be moving at (24,902 miles / 24 hours) ≈ 1038 miles per hour. If the air mass "appeared" to be stationary, it would in fact be moving at the same speed, in the same direction, so its relative velocity would be zero. Now consider a circle 24 miles in circumference, just a short distance from the north pole (a circle of latitude, in fact). A point on that circle would be moving at (24 miles / 24 hours) ≈ 1 mile per hour! That certainly suggests some complex forces and motions, no?

Rather than re-invent the wheel here, I'd recommend PhysicalGeography.net, the source of the earth's rotation image previously posted by rjgoniea, there's some great information there, such as Forces Acting To Create Wind, and much more.
 
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