Hi Friends,
I have some doubts regarding "Western cyclonic disturbances"...hope you can shed some light on it.
My Understanding -
a) These are westerlies flowing from the Meditterian region and basically cold and dry.
b) Flow in Winter when High Pressure Belt over Himalayan regions.
c) Brings rain to Northern India due to extra-tropical cyclones. (May be I'm wrong on this)
d) Affect coastal regions of India. (Orissa, WB etc)
My Doubts -
a) For extra-tropical cyclones - cold front should meet warm front. But northern India is already a high-pressure zone (so no warm front is there)
b) How is it affecting coastal regions? - My understanding was that the damage that generally happens there is due to tropical cyclonic activities and not extra-tropical cyclones.
Please clarify these doubts if one has a good understanding of "Western Cyclonic Disturbances".
PS - I may be totally wrong about a fact things...please specifically mention that so I can correct my mistakes.
Thanks in advance.
Comments
Thanks for the prompt reply ..
Just few questions?
1) Aren't these westerly supposed to be dry...as they are crossing over a continent?
2) Also can you please elaborate "Tibetan Plataeu" point...I couldn't comprehend it.. :P
3) Also, How does it affect coastal regions?
Now answer to your another question
U asked there is no fronts then how extra tropical cyclones?
Actually extra-tropical cyclone is given name to the cyclone which originates on continent or land unlike tropical cyclone which originates on large water body. And what must have studied is how tropical cyclone formed by frontogenesis and frontolysis. This doesnt mean that fronts are the only cause of extra tropical cyclones.
So now as you are also aware extra tropical cyclone are higly influenced by jet streams and they almost follow the path of jet stream.
@Therock90
Wo dry wala dekhna padega mere ko bhi...ok
by the time u can refer this also
http://www.yourarticlelibrary.com/monsoon/monsoon-classical-and-modern-theories-of-monsoon/13835/
Also i would request instead of creating news discussion we can raise/put these doubts in geography discussion
you can discuss here
http://forumias.com/discussion/2920/geography-optional-subject-mains-doubts#Item_178
1) Okay this makes sense to me...as I was originally thinking that it will cause rain but as you said they'll result in snowfall so that makes sense.
2) Also, yes i read about frontogenesis so thought that's the main diff b/w tropical and extra-tropical cyclones.
Though there is one I'm still confused about. It's the concept of tibetan plataeu.
I read this in NCERT and I'm qouting - "The Tibetan plateau gets intensely heated during summer, which results in strong vertical air currents and the formation of high pressure over the plateau"
This is how I think anti-cyclones will be formed in Tibetan region as high Pressure region is already created and Jet streams would rush into the eyes from above.
But how would "Intensely heating" create a "High Pressure Zone".? Don't you think exactly opposite should happen?
BTW thanks for sharing that link...I was actually looking for something comprehensive on this topic. I would go thru it and see if I can get clarity on this.
But if you can help then please do.
Bro as I told u earlier also in summer jetstream moves northward of tibetan plateau. This bends the jetstream like a bow ( i hope u can imagine) and it direction is always from west to east. So some part of jet stream starts making clockwise rotation and as you know anti-cyclone has clockwise rotation. The intense heating part is independent of this phenomenon it is due high altitude & sun directly over it.
As you also might be aware that anticylone sucks air from up and cyclone from the bottom.
Is your doubt clear ??
Ohk...I get what you're trying to say...but everywhere I've been reading it says that in Summer Tibetan Plateau becomes a high pressure heat zone and this produces a thermal anticyclone over this region and then this results in easterly Jet stream which flows from east to west.
The same has been given in the article that you shared with me above. Also check out this article... "
http://www.yourarticlelibrary.com/monsoon/role-of-himalayan-and-tibetan-highlands-in-the-development-of-south-west-monsoon/5465/
May be there is something that I'm missing here.
Bro, I am not sure if I am correct. I am just speculating. But if the Tibetan plateau is intensely heated, it is possible that the air near the ground is heated. But as the hot air mass rises up, it expands adiabatically and cools to produce a high pressure area. So, low pressure near the ground but high pressure in the higher layers of troposphere. This can explain many facts like:
1) Jet streams flow about 9 K.M. up in the atmosphere and not close to the earth
2) Look at the inter-tropical convergence zone, there is hot air near the ground but to complete the circulation, there is divergence in the upper layers of the atmosphere. This means that on the ITCZ, though there are low pressure conditions near the earth, there are high pressure conditions in the upper layers of atmosphere.
3) Also, anticyclones suck air from above and not below. So this makes perfect sense.
What do you think about my theory??
It will be wrong to say that western disturbances are westerlies . They do not originate over Indian subcontinent or Tibetan plateau . They are temperate cyclones which generally start in the region around Mediterranean sea by frontogenesis . The Westerlies brings these towards Indian subcontinent as they are the prevalent winds in winter over this lattitude . As they travel from Mediterranean towards continents they tend to lose most moisture on the way however give slight rain in Northwest India ( Haryana , Punjab , Western uttar pradesh )which is extremely good for RABI crops . Please note Western disturbances are simply temperate cyclones ( extra tropical ) and not westerlies .
I do not think they affect any coastal area .The winter rain in east coast is rather due to Northeast monsoon picking moisture from Bay of Bengal and offloading it on coasts .
Also extratropical cyclones are cyclones oustside tropical areas , generally temperate regions ( hence the name temperate cyclones ) they can be over sea or land.
Jetstream is a fast moving band of air , as far as I know there is no vertical motion in them( ascent or descent) . Though wobbling does occurs and often they enter lower lattitudes of temperate zone .
Any addition or rectification is welcome