Some regions have monsoon conditions, a seasonal reversal of wind due to the heating and cooling of major land masses. This is true of east Asia in particular; according to https://science.jrank.org/pages/4439/Monsoon-monsoons-South-China-Japan.html

The monsoons of China and Japan are strongly affected by the huge land mass of Siberia. During the winter, the interior of Siberia becomes extremely cold. Cold air is dense, so a cold area of high pressure forms, where the air sinks from aloft. When it reaches the surface, the air spreads outward in all directions. The result is a dry winter monsoon that blows from the north through south China and southeast Asia. The same circulation affects northern China, Japan and Taiwan, where the prevailing wind is from the northwest.

But that description seems like it should also apply to North America, with the interior of Canada becoming likewise extremely cold. Why is the east coast of North America not similarly subject to a dry winter monsoon?

(I have seen it argued that this is because the polar vortex prevents cold air spilling down over North America. But then the question becomes, why does the polar vortex behave this way over that continent, but not over Asia?)

  • 1
    $\begingroup$ @nwallace - East Asia gets winter monsoon due to en.wikipedia.org/wiki/Siberian_High . $\endgroup$
    – gansub
    Jul 22 '21 at 9:58
  • $\begingroup$ @gansub Okay but then why is there no corresponding Canadian high to do the same thing in North America? $\endgroup$
    – rwallace
    Jul 22 '21 at 16:51
  • 1
    $\begingroup$ @rwallance The North American winter climate is a complex one. The stationary feature there is the polar vortex and the Aleutian Low.en.wikipedia.org/wiki/Aleutian_Low $\endgroup$
    – gansub
    Jul 22 '21 at 17:09
  • $\begingroup$ @gansub Right. So why does North America have the polar vortex and the Aleutian low instead of a Canadian high? Looking at the linked articles and the maps thereon, the only thing that jumps out at me as a possible cause is that Siberia is simply bigger than Canada? $\endgroup$
    – rwallace
    Jul 22 '21 at 18:12

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