I just
looked at my flight itinerary and it’s a 10 hour flight, but I thought it was 9
hours! Air Canada, you’ve managed to piss me off again. But in all seriousness,
why is the flight back to the States longer? No, it’s not reverse culture shock
and missing Italy (well possibly), nor is the plane mechanically slower. Believe
it or not, it’s actually because of the Earth. More specifically, a natural phenomenon
called the “jet stream” acts as a force that helps propel (or in some cases,
slow down) aircraft at certain altitudes along a particular corridor in the
Northern hemisphere. While the jet stream
is normally associated with its impact and purpose in the field of aviation, it
also plays a significant role in meteorology, affecting weather patterns, and
even has military usages, such as aiding fighter jets and driving unmanned
weaponry.
The jet
stream seems to be a crucial aspect in our lives and has definitely served
society a great deal of usages, but how does it work exactly, there must be
some science and logic behind it. Simply put, the jet stream is basically a path
of high-speed air current that circles the Earth. To be more accurate, it’s not
a single jet stream, but in actuality, there are really multiple jet streams on
Earth and they even exist in the atmosphere of other planets. In the Earth’s atmosphere,
there are in total four major jet streams, two in each of the Northern and Southern
hemispheres: Polar jets and Subtropical jets. Of the two, the Polar jets are
stronger and located at lower altitudes than the somewhat weaker Subtropical
jets (7-12 km and 10-16 km above sea level respectively). Regardless, jet
streams can have speeds up to several hundred miles per hour; speeds over 247
mph have been recorded. These main jet streams are located in a layer of the
atmosphere wedged right between the troposphere and the stratosphere called the
tropopause. The jet stream is several thousand miles long and a few hundred
miles wide, but the thickness is relatively miniscule, only a mere few miles.
So in order to harness or avoid the jet stream, airplanes have a narrow window
in terms of altitude to aim for, but also have a wide path that can be taken
for an extensive period of time, assuming travel from West to East.
So,
what exactly causes this massively intense, high-speed force that can accelerate
aircraft and why does it travel from West to East? These two factors of the jet
stream are actually interrelated and are derived from a combination of two
aspects of the Earth. The foundational bases of the jet stream are the Earth’s axial
rotation and the temperature difference between two air masses. The requirement
for air masses with a temperature difference basically dictates where the jet
stream is located. In the case of the Northern hemisphere, the jet stream is
primarily located between the latitudes of 30⁰N and 60⁰N
because that is the area where the cold Arctic air mass meets the warm tropical
air mass. The jet stream also shifts according to the season and the weather; generally
speaking, there is a shift north in warm weather and south in cold weather.
Also, the jet stream is stronger in the winter than in the summer due to the
greater temperature difference between the air masses. The temperature
difference between the air masses is not exactly the direct cause of the jet
stream, but there is a clear, distinct connection. To begin, air masses of
different temperatures have different densities, cold air being denser than
warm air, providing an air pressure difference. At higher altitudes in the
atmosphere, the air pressure simple continues to escalate and grow. The air
pressure difference causes winds that desire to flow from the warmer air to the
colder air, from high pressure to low pressure. If this logic works, then the
winds should flow vertically from the warmer southern air mass to the colder
northern air mass. However, this doesn’t hold true, the jet stream flows
horizontally along the boundary of the air masses. This is where the spin of
the Earth comes into play. The Earth’s axial spin causes a natural marvel
called the Coriolis Effect, which basically deflects the winds to flow along
the air masses. The Coriolis Effect causes the winds to turn right and flow
from West to East, not into the opposing air mass. Overall, the jet stream is
strong winds produced from temperature differences and the Coriolis Effect.
Now
that we understand why the plane ride back home will be longer, not cause of
the airline, but instead we will be on the plane longer because of the jet
stream from the Earth. Rather than being mad at the airline on the whole ride
home, we should sit back, relax, and simply remember all the great times we’ve
had in Italy over these past 6 weeks. (But I’ll still be pissed at Air Canada
for my 8 hour layover…)
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