Rosby wave

Please help!!! I just don't understand it - can anyone explain to be in the most basic way possible what it does/is?
Thanks rosiex

Reply 1

Lynnie

this is what i think:
it is a loop within a jet stream exaggerated by coriolis, prob wrong my teacher sucks so i need help too

Reply 2

supernoodle

the only info i have is that is is a band of upper air westerlies (sp?)
so it occurs between 30-60 latitiude. i also includes some jet streams. i'm unsure where this would be included in a question thou

x

Reply 3

toto8462

9

I pulled this from one of my previous posts in another thread. Hope it helps.

Below is a quick summary of upper atmospheric winds.

The earth receives differential heating and so there is a pressure gradient force driving air from the equator polewards. However, the coriolis force defflects this to the right (in the northern hemisphere) and so it flows west to east around the globe at the highest level (the tropopause boundry). It is known as a geostrophic wind. This air is not deflected in anyway and flows continuously around the globe.

However, as more and more air comes from the equator, the geostrophic winds become rossby waves. This is becasue the geostrophic winds get deeped and deeper. They cannot become much wider because it is located at the polar front and the difference in pressure stops the geostrophic wind spreading laterally. As it gets deeper and deeper, it becomes much lower in the atmosphere and mountain ranges interfere with the geostrophic winds. As the air passes over mountains, its velocity increases and so the effect of the coriolis force increases and deflects the wind to the right. The winds are now on a trak southwards, but the pressure gradient force gets larger and larger as you go south and so the winds are deflected north again, creating waves which circle the globe. These waves are known as rossby waves.

Now - Jet streams are much more narrow than geostrophic winds or rossby waves, they are found on the most northerly and southerly edges of the geostrophic winds/rossby waves. The northerly one is called the polar jet stream and the southerly one is called the sub-tropical jet stream.

The polar jet steam seperates the polar and ferrel cells. The sub-tropical jet stream separates the ferrel and hadley cells. Depending on the temperature differences between the cells, the jet streams are of different speeds. i.e. the greater the difference, the faster they flow.

A note on formation of depressions/anticyclones. Jet streams within rossby waves slow down going south towards the equator (due to the pressure gradient force) and so there is a build up of air. Air cannot indefinitely move sideways (air mass fronts prevent this), it cannot move up (tropopause - uniform density prevents air rising) and so it can only move down. This decending air is rotated clockwise (looking down over the north pole) due to coriolis force. Thus you have an anticyclone.

In a similar way, the pressure gradient force drives the jet streams going north, so they speed up. Because jet streams are generally slower around the bends in the rossby waves, on the ascending limb, there is a shortage of air and so it is drawn up from the ground (in an anticlockwise fashion). Thus you have a depression.

The application of this, is that you will notice that depressions follow the path of jet strems (not surprisingly!). If you monitor upper air movements, you can begin to predict the likely path of a depression.

Reply 4

Lynnie

so are jet streams in rossby waves or vice versa

Reply 5

~*Sar*~

1

Well in the formation of a depression pronounced rossby waves produce strong jet streams, which leads to more activity in the polar front. So i was under the impression Rossby waves form jet streams....
argh, i dunno

Reply 6

toto8462

9

~*Sar*~

Well in the formation of a depression pronounced rossby waves produce strong jet streams, which leads to more activity in the polar front. So i was under the impression Rossby waves form jet streams....
argh, i dunno

Ok, my teacher said that rossby waves are the bends in the geostrophic winds, that circle the globe, (the browny coloured patch between the blue and red jet streams). The jet streams are at the edges of the geostrophic winds.

Reply 7

Spiral

I've got that:

Rossby waves are a belt of upper air westerlies, which follow a meandering path.
Their velocity is not uniform.

Within Rossby Waves are very fast jet streams.
Jet streams are strong regular uniform winds in the upper troposphere, flowing in a narrow band from West to East.

Rosby wave

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