How do jet streams work?

Jet streams are currents of fast-moving air that can be found high
in the atmosphere of some planets. Here on Earth, when we
refer to ‘the jet stream’, we’re typically talking about either of the
polar jet streams. There are also weaker, subtropical jet streams located
higher up in the atmosphere, but their altitude means they have less
of an eff ect on commercial air traffi c and the weather systems in
more populated areas. The northern jet stream travels at about 161-322
kilometres (100-200 miles) per hour from west to east, ten kilometres
(six miles) above the surface in a region of the atmosphere that is
known as the tropopause (the border between the troposphere and
the stratosphere).
It’s created by a combination of our planet’s rotation, atmospheric
heating from the Sun and the Earth’s own heat from its core creating
temperature diff erences and, therefore, pressure gradients along which
air rushes. In the northern hemisphere, the position of the jet stream
can aff ect the weather by bringing in or pushing away the cold air
from the poles. Generally, if it moves south, the weather can turn
rather wet and windy; too far south and it will become much colder
than usual. The reverse is true if the jet stream moves north, inducing
drier and hotter weather than average as warm air moves in from the
south. In the southern hemisphere, meanwhile, the jet stream tends to
be weakened by a smaller temperature contrast created by the greater
expanse of fl at, even ocean surface. However, on occasion it can also
impact the weather in the same way as the northern jet stream does.