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I've heard meteorologists say that the cold air masses that reach South America during the winter months don't originate in the polar region. I always thought they crossed the strait of Drake and reached the continent at Tierra del Fuego. From there, depending on their strength, they might reach very low latitudes. If these cold air masses don't come from Antarctica, where do they come from?

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  • $\begingroup$ South American winter is from June 21 through September 21st. $\endgroup$ – gansub Jul 27 '16 at 4:41
  • $\begingroup$ @gansub Yes, and John Lennon died at the age of forty. $\endgroup$ – Centaurus Jul 27 '16 at 14:23
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    $\begingroup$ It can be confusing because a lot of times people in NH forget about this. When I first read this I was immediately thinking the winter months in NH and I had to remind myself this question is about winter in SH. No offense meant. $\endgroup$ – gansub Jul 27 '16 at 15:09
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    $\begingroup$ @gansub None taken. But let me remind you that meteorological phenomena are not regulated by the calendar. Winter in the SH is the time whe insolation is shorter, and those months could have been given any names or any dates. Scientists chose to call those specific months "June, July, August...but imho this has nothing to do with the formation and migration of cold air masses. In a nutshell, to say that winter in SH is from ..to...is irrelevant since winter is always winter irrespective of the months we have chosen for it both in the NH and SH. Even without any existing calendar we can still $\endgroup$ – Centaurus Jul 27 '16 at 15:52
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The Pacific coast of South America is affected by the Humboldt Current, a wind-driven "upwelling" system running counterclockwise that is cold and windy but nutrient rich..

The "six o'clock" position indeed touches Antarctica, and then the right edge of the "clock" reaches Chile, Peru, Ecuador, and Colombia, as far north as the Galapagos Islands near the equator, making those areas cooler than equivalent latitudes on the Atlantic coast.

The reason the currents don't "originate" in the Antarctica is because they are part of a circular system that spans a whole ocean in the southern hemisphere. But they "make stops" there.

The ocean and atmosphere mutually interact to create a "coupled" system that brings about the so-called ENSO El Nino (La Nina) Southern Oscillation, with its characteristic weather changes.

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  • $\begingroup$ can you add how this current affects El Nino or La Nina ? We have a coupled system right ? $\endgroup$ – gansub Jul 28 '16 at 9:22
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    $\begingroup$ Could you answer the question? Where do the cold air masses come from and how do they make their way to the Argentinean and Brazilian atlantic coast? $\endgroup$ – Centaurus Jul 28 '16 at 16:39
  • $\begingroup$ @Centaurus: It's a circular, counterclockwise process, with one "clock" in the Atlantic ocean and the other in the Pacific Ocean. See my link to the Humboldt current for more details. Brazil and Argentina are on the west side of the Atlantic "clock" so they receive hot, moist air from the tropics; west Africa gets cold air from the Antarctic. $\endgroup$ – Tom Au Jul 28 '16 at 16:45
  • $\begingroup$ Tom, you seem to have missed my question. During the winter months a cold or very cold air mass reaches central Argentina and from there, depending on the barometric pressure at its core, it migrates north, Sometimes these masses move north along the Atlantic coast and may reach 10-15ºN in Brazil and other times when they are massive, they move north along the Atlantic coast as well as along the central parts of the continent and may even reach the southern parts of Amazonia. $\endgroup$ – Centaurus Jul 28 '16 at 17:07
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    $\begingroup$ Why would the cold air mass need to come from somewhere outside of the region? Cold does not really need an outside origin, it is the absence of warm. In winter conditions, non-tropical locations will experience cold due to the absence of solar or stored thermal effects unless they receive warming currents. $\endgroup$ – dlb Aug 1 '16 at 17:35

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