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Breezing Along with

Wind Systems

Picture
Screenshot from https://earth.nullschool.net/#current/wind/isobaric/1000hPa/winkel3
Over the course of writing previous pages on Earth systems for this site, I've tangentially stumbled into the wind.  No matter where I happen to be researching, it plays some key role in how something works.  Dispersing plants throughout the planet?  Wind propagation was key before other organisms helped move plants around.  How waters move across the surface of the ocean?  The wind helps move these waters in addition to underwater ocean currents.  How does rain not just fall right back onto the ocean?  Through wind pushing clouds over the land in a process called advection.  How areas without water move minerals over geologic time?  That would be wind erosion.

It seems like this miraculous thing that a brunt of other important Earth systems depend upon.  It also seems like it just happens to work, something we're just lucky to have on our planet.  While this is slightly true, how our wind system works does follow a certain set of rules.  As wonderful as it is to have wind on the Earth and we are lucky as to how it is tuned to operate, it is far from a magic trick.

Let's dive in!

How Wind Occurs

A good place to start is understanding a bit of physics.  Our atmosphere is made of particles that comprise the air we breathe.  As is the case with all matter, even small stuff like particles of air, it can be acted on by outside forces.  One of these forces being exerted on the Earth's atmosphere (and land for that matter) is heat.  The Earth gets heated up by energy reaching the planet from the sun.  What makes this a bit more interesting, though, is that the Earth is constantly rotating.  It's also a massive sphere.  The sun's light doesn't hit all parts of the Earth consistently.  This leads to differences in heat at different parts of the planet.
If we can recall some physics knowledge, heat likes to move from hotter areas to cooler areas.  Additionally, matter under high pressure likes to move to areas of lower pressure.  In areas of the Earth where the atmosphere is warmer, air will move towards a cooler area.  In areas of the Earth where the atmosphere is under high pressure, the air will move towards areas of lower pressure.  So what do we call it when air moves again?

Oh right, wind!
Air moves from hot to cold and high-pressure to low-pressure areas, creating wind
But why doesn't the wind move in straight lines between these areas then?  Nothing in physics suggests that particles will take an indirect path to its desired location.  Well, similar to when we covered ocean currents, this is due to the Earth's rotation.  Because the planet is always rotating, a directional force is always being applied to how particles move due to temperature and pressure.  This rotational effect on wind and water, in particular, is known as the Coriolis Effect and it's what makes winds tend to move clockwise in the southern hemisphere and counter-clockwise in the northern hemisphere.
From the equator, wind travels clockwise to the south and counter-clockwise to the north resulting in winds around the equator always coming from the east!

Distribution of Wind on Earth

The Earth's wind system is a bit more complex than that though.  Beyond differences in northern and southern hemispheres, air travels only a fraction of the distance of that hemisphere in either direction.  We have heat-driven movement starting from the equator and pressure-motivated movement from the poles. Each of these only makes it roughly a third of the way towards the other.  The section between these major movement areas act like a gear, circulating air between them and in the opposite direction than the surrounding areas.

The area moving air from the equator is called the Hadley Cell or Trade Winds.  These are the most active wind areas on the planet, conducive to many a tropical storm.  At the equator, however, there is a much quieter band of wind activity aptly named the Doldrums.  Wind activity in this area is sparse and inconsistent.  There is no prevailing wind direction here.  Where the trade winds meet the middle bands in the hemispheres are also particularly wind-deprived areas.  These occur at around 30-35 degrees north and south of the equator and are named the Horse Latitudes.
At the poles, we have the Polar Cells or Polar Easterlies.  These are the pressure-driven wind areas in either hemisphere, moving air from the poles back toward the equator.  The band in between these 2 cells is called the Ferrel Cell or Prevailing Westerlies.  Because either side of this cell is rotating in one direction, this cell rotates opposite of those serving as a "wind gear" connecting the heat and pressure wind cells.

These are the primary ways that air moves about the atmosphere on a global scale, but most anybody can tell you they've felt a breeze coming from any direction, not just the prevailing ones described above.  Even though the prevailing westerlies are the only bands with "prevailing" in their name, the other bands (with the exception of the doldrums and horse latitudes) also have prevailing wind direction.  Prevailing just means that's the general tendency of the wind direction, but it doesn't always move that way.  Changes in pressure and temperature can change wind direction on a local scale causing all sorts of interesting activity and phenomena.

Wind Phenomena

Speaking of phenomena, wind can get fairly wild on the Earth.  Radical changes in pressure and temperature take make some interesting things happen.  Despite these wind activities being destructive, some of them have become things even humans depend on to make normally inhospitable places more hospitable.

Hurricanes

​Depending on where you're from, these can go by a number of names.  Severe tropical storms, hurricanes, typhoons, they all describe the same type of wind phenomena, all of them initiating from the band of wind activity originating off of the equator.  While it is possible for them to form in a few ways, they generally follow the same life cycle.  They start as a tropical disturbance, where thunderstorms begin to develop over the ocean with no major cyclical wind activity.  If the storms maintain themselves until a cyclone can stay consistently formed, an "eye" of the storm can form.  This phase is called a tropical depression for this eye formation, higher winds concentrating toward that center point of low air pressure.
Hurricanes can be ridiculously destructive forces when they reach land.

Earth's fastest recorded wind speed was during a hurricane, clocking in at 408 km/h (254 mph)!
From here onward, intensity is the gauge for names.  If the tropical depression reaches maximum sustained wind speeds of 63-117.5 km/h (39-73mph), it is reclassified as a tropical storm.  If the storm proceeds to intensify beyond that range, it is again reclassified as a hurricane/typhoon/severe tropical storm.  Classification goes even further, defining categories of intensity that gauge the destructive force of the wind wrapped up in the storm.
Sorry, your browser doesn't support embedded videos.
Video hosted by NOAA at https://www.nhc.noaa.gov/aboutsshws.php

Tornadoes

Tornadoes are a land-based wind phenomenon that tend to form in the most severe of thunderstorms, classified as "supercells."  These supercells have what is known as a rear flank downdraft (RFD for short) where dry air wraps the back of these storms where mesocyclones can form.  These RFDs act as inflows for warm air, intensifying cyclical air activity under the storm cloud.
Tornadoes are a common occurrence in the Great Plains of the United States of America thanks to the wind relationship coming from Canada to the north and the Gulf of Mexico from the south
​When this mesocyclone reaches low enough from the storm, it will pull up dirt and land particles from the ground in the moment we tend to call a "tornado touchdown" (no relation to American football, just the moment the mesocyclone touches the ground from above).  From here, the tornado will continue following the path of the storm cloud it formed from, the air inflow from the RFD cooling over time.  When this inflow no longer has warm enough air powering the cyclone, the tornado will enter a dissipating phase, breaking into rope-like tendrils that disappear back into the atmosphere.  While these are not nearly as large as tropical storms, they can be just as destructive and are also categorized based on this destructive force.  The highest classification reaching up to 609 km/h (379mph)!

Monsoons

Growing up, I always associated rain with a monsoon, but the core of this phenomenon is wind.  Despite the destruction this storm can bring, it also enables wet/dry seasonality to normally very dry areas of the world.  Even among human populations, we depend on monsoon activity to bring in annual rains for our crops in more tropical areas of the world.  Monsoons occur when the prevailing wind direction goes through a seasonal change, moving from cold, high-pressure areas to warmer low-pressure areas.  Along with this wind direction shift comes a slew of rainstorms defining the seasons for areas that deal with this annual phenomenon.​

Humans & the Wind

Suffice to say, the wind is an integral part of the Earth's systems.  Wrapped up in all the work they do, they can do some serious damage to ecosystems that they pass through.  Though without the wind system, we wouldn't have a majority of other systems that all living things benefit from on Earth.  Even though this seems like a hulking hyperobject of a concept, we've seen how it still follows some basic principles of physics.
Humanity, while we might not always realize the effects of our activities over time, have caused significant shifts in both of the properties we went over earlier: atmospheric heat and pressure.  By emitting a bunch of carbon dioxide into the atmosphere much faster than geologic time has historically allowed and the planet's organisms have adapted to, we have both modified atmospheric pressure and the heat the Earth is exposed to from the sun.  Local wind phenomena have become less predictable and more chaotic as a result.  The general rules that we discussed above become more malleable over time, changing how the planet's wind system acts.
Human emissions alter atmospheric heat and pressure causing the balance of Earth's wind system to shift
If these kinds of emissions continue at the rate we've been going, we could start moving where wind activity occurs.  The tropical region of the planet may expand further from the equator, making hurricanes a common occurrence in what is now the westerlies bands.  Tornadoes, a common event in the westerlies will move further toward the poles.  And new phenomena we can't even fathom could form in our new hyper tropical regions around the equator.  Continuing with these heat and pressure shifts moves the needle on where these events occur, forcing climate migrations to hospitable zones.
​
And that's assuming our existing rules function as these wind bands shift.  It could be that our planet's wind system only operates with 3 bands, depending on the "westerlies" gear between the poles and the tropics.  It's entirely possible that an increasingly intensified hyper-tropic region makes the planetary wind system fall apart or reform some new pattern changing global weather patterns for good.  Or at least a good long while.


Systems like the wind on a planetary scale are always a good reminder of the kind of power humans have.  We don't control our planet, we just accidentally stumbled into knobs and levers that influence how the planet behaves.  There is so much that the Earth does that makes life on it, for us, possible.  We know a bit more now about how we impact our planet's wind, enough to know that we should be taking measures to halt the changes we make.  While we can't necessarily change the knobs and levers we've found, we know where they are and how to read them now.  It's up to us to use this knowledge to the benefit of our home so we can continue to call it home for the foreseeable future.
~ And, as always, don't forget to keep wondering ~
Prismatic Planet
Sources
Interactive Wind Map
vvv Check this out, it's super cool vvv
https://earth.nullschool.net/#current/wind/isobaric/1000hPa/orthographic

​
Wind Systems
https://manoa.hawaii.edu/exploringourfluidearth/physical/atmospheric-effects/wind-systems
https://www.nationalgeographic.org/encyclopedia/wind/

Phenomena
https://sciencestruck.com/tornado-life-cycle
http://tornadoes-neramsoltani.weebly.com/life-cycle-of-a-tornado.html
http://plainshumanities.unl.edu/encyclopedia/doc/egp.pe.061
http://hurricanescience.org/science/science/hurricanelifecycle/
https://www.nhc.noaa.gov/aboutsshws.php
https://www.thoughtco.com/what-is-a-monsoon-3444088
https://www.nationalgeographic.org/encyclopedia/monsoon/

Human Impact
​
https://www.sciencedaily.com/releases/2021/04/210419094035.htm

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