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[Query] Breaks in Monsoon

edited July 2014 in Geography & Geology
I could not find out what causes BREAKS IN MONSOON?

How does the monsoon trough/ITCZ undergoes change to cause Monsoon Breaks ?
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Comments

  • Due to the movement of the ITCZ from Central India to the foothills of the Himalays/Shivaliks, there is a monsoonal break in rainfalls in Central and Southern India. This break may extend froma few days to a few weeks.

    However, during this period, there is enhanced rainfall in the Tarai region and the Himalayan foothills.
  • Is it someway related to weakening of Tibetan High. As the Tibetan High weakens, the tropical easterly also weakens causing monsoon winds to weaken ?

    or is it that Tibetan High and ITCZ shift enforce each other ?
  • No, it is an intra-seasonal variability. During this season, the Tibetan High is more or less consistent. There may be some vagary there as well but there is no concrete corroborative data on their correlation as such.
  • I think, even ITCZ is almost constant. It gets shifted from central India by June, and remains there.
    'Break' and 'Burst' phenomena is caused by shifting of 'monsoon trough', which is altogether different than ITCZ.
    The phenomena is best explained at

    http://www.cherrapunjee.com/monsoon-magic/movement-of-the-monsoon-trough-and-breaks-in-the-monsoon/
  • The Monsoon Trough movement and the ITCZ movement are inextricably linked, ck. The Monsoon Trough would not extend from Kolkata to Karachi until and unless the ITCZ pulls it towards itself.

    But, yes. I correct myself. Use of the term 'Monsoon Trough' would be more appropriate.
  • Yes, the two are interlinked. I got confused. :-(

    @Neanderthal
    A doubt: " The Westerlies that come to Britain and Norway tend to be cool winds in the summer and warm winds in winter and are most valuable in moderating the climate." (Pig 107, GC Leong)

    I understand that it is due to shift in ITCZ and Britain's particular location in 40-60N latitude. But I have been wondering, how cool wind and warm wind?
  • Okay, it's rather very simple-

    During the Northern Hemisphere summers, the ITCZ shifts northwards and therefore the entire wind system shifts- the least affected being the Polar Easterlies. As a result, the Westerlies pick up moisture from the Atlantic Ocean and reach North-Western Europe as on-shore cool moisture-laden winds. Similarly in the NH winters, these winds are dry winds which do not carry any moisture but drag the warm tropical waters in the form of North Atlantic Current (which breaks into the Norwegian and Irminger currents) thereby moderating the severe European winters. As a result, the ports of North-Western Europe are more or less operational almost throughout the year.
  • "Similarly in the NH winters, these winds are dry winds" - Why these winds are dry ? Is it because during winters less surface heating (SST) leads to less atmospheric humidity?

    And similarly the summers lead to high moisture caused by high SST (high evaporation) ?
  • Predominantly. Also, due to the southward displaced ITCZ during NH winters, the winds are at a higher atmospheric pressure and thus have low moisture carrying capacity.
  • Okay, it's rather very simple-

    During the Northern Hemisphere summers, the ITCZ shifts northwards and therefore the entire wind system shifts- the least affected being the Polar Easterlies. As a result, the Westerlies pick up moisture from the Atlantic Ocean and reach North-Western Europe as on-shore cool moisture-laden winds. Similarly in the NH winters, these winds are dry winds which do not carry any moisture but drag the warm tropical waters in the form of North Atlantic Current (which breaks into the Norwegian and Irminger currents) thereby moderating the severe European winters. As a result, the ports of North-Western Europe are more or less operational almost throughout the year.
    I had missed the point that Polar easterlies can play a crucial role in dragging the North Atlantic drift to Britain and Scandinavian ports. (I only believed that polar hasto be cold.) Thanks a lot :-)

    You are a savior.

    Another question:
    GC Leong says that there are three types of rainfall: Convectional, Orographic and Frontal. Now, which category should I put monsoon into? Is a mix of three, or a new category altogether.
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