Originally Posted by CanisLupusArctos
North Atlantic Oscillation... Pacific Decadal Oscillation... Solar Cycle...
These are three major players in what kind of winter we get, here in New England. They aren't the only three, but they're big.
The solar cycle affects the weather of the whole earth. It gets hotter, and it cools down. It doesn't burn at the same temperature all the time -- like any other fire. The sun goes in 11 year cycles. When the sun gets hotter, there are more sunspots, and flares of various classes and magnitudes. When it cools off, it goes spotless, and flares become a rare occurrence. Flares cause northern lights, telecom signal disruptions, etc. Sunspots are a visual indicator of how much power the sun's putting out.
Then you have the ocean cycles. The most basic way to explain it is to start by saying the lake has its "turnovers." It changes out its water. The water freezes and thaws, warms up and cools down. Being a small body of water, the lake goes through its cycles quickly. The oceans do cycles too. But, because they're MILES deep in places, they have a lot more water than the lake does, and take that much longer to run their cycles. It's way more complicated than that, but for the layperson that is the main idea of it.
The Pacific Decadal Oscillation takes years to go through. Being the largest body of water on earth, it has more say in the weather on earth than any other body of water. When the Pacific produces a seasonal cycle it affects weather on earth for just that season. El Nino is seasonal warming of PART of the Pacific waters, and La Nina is seasonal cooling of those same waters. The whole ocean itself goes through a multi-year warm phase or cold phase, and that affects weather on earth.
The Atlantic has its own warm and cold phase called the Atlantic Multidecadal Oscillation. The North Atlantic Oscillation (that SIKSUKR commented on) is an atmospheric feature normally found (drumroll please...) over the North Atlantic. It's a smaller gear in the much larger "air machine" of the Arctic region.
Air flows as a fluid, like water does. A blimp and a submarine look pretty similar. The wings on an airplane resemble the fins on a shark. The atmosphere is fluid, like the ocean. Something doesn't have to be liquid to be fluid.
Cold air (found at the poles) is heavier than the air away from the poles. The cold air spills away from the poles like waves rolling up on the beach, with winter being "high tide" and summer being "low tide." The cold air pushes the lighter air out of its way and generates eddy-filled "wake turbulence" in the process. Each "eddy" is a spinning area of low pressure (in the middle of a whirlpool you can SEE that there is less water-- low water pressure is there. Same is true of air except you can't see it.)
When a wave of cold air rolls away from the pole, the warmer (lighter) air gets displaced-- the same "gravity-fed" concept that makes you feel a chilly draft in your 72-degree downstairs if you open up the 58-degree guest room upstairs. Warm air doesn't "rise," because nothing on earth rises without help. Air of a certain temperature is like any other material --it wants to be as close to the center of the earth as it can. Things layer away from the center of the earth by order of density, and temperature affects density. 69-degree lake water gets forced upward until there is 70-degree water above it. A life jacket gets pushed up to the surface of the water but no higher -- it's less dense than any of the water but more dense than air. An air bubble from a diver pops at the surface and keeps rising through the air until it reaches the height at which it "floats."
The air, flowing as a fluid, does not spill away from the poles evenly. We're spinning on a sphere-shaped planet made of different things, some of which absorb or reflect heat better than others. The air (held down by gravity) is in contact with them, and is constantly getting tugged along by friction from the surface of the earth. Therefore, the air spills away from the poles UNevenly... like wax from the top of a candle. Where it "drips" varies all the time. That general concept gives us "oscillation" in the polar air.
Again, it's a *general* concept and gets way more complicated than that, but for the layperson, that's the main idea of clashing air masses and weather.
Air and water behave as wobbly blobs, constantly in motion on an ever-spinning earth that is constantly being heated UNevenly by exposure to a nearby space fire.
We have detected patterns within the movements of those wobbly blobs -- some that last days, and some that last decades. There are probably more that we don't know about. All of them are ingredients in the recipe for our weather. We have named the ones we know about, and that's where we get titles like, "North Atlantic Oscillation."
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