Download The Coriolis Effect

The
Coriolis
Effect
Quin
és
correcte
?
In
the
iner5al
frame
of
reference
(upper
part
of
the
picture),
the
black
object
moves
in
a
straight
line,
without
significant
fric5on
with
the
disc.
However,
the
observer
(red
dot)
who
is
standing
in
the
rota5ng
(non‐
iner5al)
frame
of
reference
(lower
part
of
the
picture)
sees
the
object
as
following
a
curved
path
due
to
the
Coriolis
and
centrifugal
forces
present
in
this
frame.
•  In
physics,
the
Coriolis
effect
is
a
deflec5on
of
moving
objects
when
they
are
viewed
in
a
rota5ng
reference
frame.
•  In
a
reference
frame
with
clockwise
rota5on,
the
deflec5on
is
to
the
leJ
of
the
mo5on
of
the
object;
in
one
with
counter‐clockwise
rota5on,
the
deflec5on
is
to
the
right.
•  The
mathema5cal
expression
for
the
Coriolis
force
appeared
in
an
1835
paper
by
French
scien5st
Gaspard‐
Gustave
Coriolis,
in
connec5on
with
the
theory
of
water
wheels,
and
also
in
the
5dal
equa5ons
of
Pierre‐Simon
Laplace
in
1778.
•  Even
earlier,
Italian
scien5sts
Giovanni
BaYsta
Riccioli
and
his
assistant
Francesco
Maria
Grimaldi
described
the
effect
in
connec5on
with
ar5llery
in
the
1651
Almagestum
Novum,
wri5ng
that
rota5on
of
the
Earth
should
cause
a
cannon
ball
fired
to
the
north
to
deflect
to
the
east.[1]
•  Early
in
the
20th
century,
the
term
Coriolis
force
began
to
be
used
in
connec5on
with
meteorology.
•  The
Coriolis
effect
is
caused
by
the
rota5on
of
the
Earth
and
the
iner5a
of
the
mass
experiencing
the
effect.
•  Newton's
laws
of
mo5on
govern
the
mo5on
of
an
object
in
a
(non‐
accelera5ng)
iner5al
frame
of
reference.
•  When
Newton's
laws
are
transformed
to
a
rota5ng
frame
of
reference,
the
Coriolis
and
centrifugal
forces
appear.
•  Both
forces
are
propor5onal
to
the
mass
of
the
object.
The
Coriolis
force
is
propor5onal
to
the
rota5on
rate
and
the
centrifugal
force
is
propor5onal
to
its
square.
•  The
Coriolis
force
acts
in
a
direc5on
perpendicular
to
the
rota5on
axis
and
to
the
velocity
of
the
body
in
the
rota5ng
frame
and
is
propor5onal
to
the
object's
speed
in
the
rota5ng
frame.
•  This
force
is
termed
either
iner5al
force,
fic55ous
force
or
pseudo
force.[2]
It
allows
the
applica5on
of
simple
Newtonian
laws
to
a
rota5ng
system.
•  It
is
a
correc5on
factor
that
does
not
exist
in
a
true
non‐accelera5ng
"iner5al"
system.
•  Perhaps
the
most
commonly
encountered
rota5ng
reference
frame
is
the
Earth.
•  Because
the
Earth
completes
only
one
rota5on
per
day,
the
Coriolis
force
is
quite
small,
and
its
effects
generally
become
no5ceable
only
for
mo5ons
occurring
over
large
distances
and
long
periods
of
5me,
such
as
large‐scale
movement
of
air
in
the
atmosphere
or
water
in
the
ocean.
•  Such
mo5ons
are
constrained
by
the
2‐dimensional
surface
of
the
earth,
so
only
the
horizontal
component
of
the
Coriolis
force
is
generally
important.
•  This
force
causes
moving
objects
on
the
surface
of
the
Earth
to
appear
to
veer
to
the
right
in
the
northern
hemisphere,
and
to
the
leJ
in
the
southern.
•  Rather
than
flowing
directly
from
areas
of
high
pressure
to
low
pressure,
as
they
would
on
a
non‐rota5ng
planet,
winds
and
currents
tend
to
flow
to
the
right
of
this
direc5on
north
of
the
equator,
and
to
the
leJ
of
this
direc5on
south
of
it.
•  This
effect
is
responsible
for
the
rota5on
of
large
cyclones
(see
Coriolis
effects
in
meteorology).
Eötvös
Effect
•  The
prac5cal
impact
of
the
Coriolis
effect
is
mostly
caused
by
the
horizontal
accelera5on
component
produced
by
horizontal
mo5on.
•  There
are
other
components
of
the
Coriolis
effect.
Eastward‐traveling
objects
will
be
deflected
upwards
(feel
lighter),
while
westward‐traveling
objects
will
be
deflected
downwards
(feel
heavier).
•  This
is
known
as
the
Eötvös
effect.
This
aspect
of
the
Coriolis
effect
is
greatest
near
the
equator.
The
force
produced
by
this
effect
is
similar
to
the
horizontal
component,
but
the
much
larger
ver5cal
forces
due
to
gravity
and
pressure
mean
that
it
is
generally
unimportant
dynamically.
•  In
addi5on,
objects
traveling
upwards
or
downwards
will
be
deflected
to
the
west
or
east
respec5vely.
This
effect
is
also
the
greatest
near
the
equator.
Since
ver5cal
movement
is
usually
of
limited
extent
and
dura5on,
the
size
of
the
effect
is
smaller
and
requires
precise
instruments
to
detect.
Geostrophic
wind
•  The
geostrophic
wind
is
the
theore5cal
wind
that
would
result
from
an
exact
balance
between
the
Coriolis
effect
and
the
pressure
gradient
force.
•  This
condi5on
is
called
geostrophic
balance.
•  The
geostrophic
wind
is
directed
parallel
to
isobars
(lines
of
constant
pressure
at
a
given
height).
This
balance
seldom
holds
exactly
in
nature.
•  The
true
wind
almost
always
differs
from
the
geostrophic
wind
due
to
other
forces
such
as
fric5on
from
the
ground.
Thus,
the
actual
wind
would
equal
the
geostrophic
wind
only
if
there
were
no
fric5on
and
the
isobars
were
perfectly
straight.
•  Despite
this,
much
of
the
atmosphere
outside
the
tropics
is
close
to
geostrophic
flow
much
of
the
5me
and
it
is
a
valuable
first
approxima5on.
•  Air
naturally
moves
from
areas
of
high
pressure
to
areas
of
low
pressure,
due
to
the
pressure
gradient
force.
•  As
soon
as
the
air
starts
to
move,
however,
the
Coriolis
"force"
deflects
it.
•  The
deflec5on
is
to
the
right
in
the
northern
hemisphere,
and
to
the
leJ
in
the
southern
hemisphere.
•  As
the
air
moves
from
the
high
pressure
area,
its
speed
increases,
and
so
does
its
Coriolis
deflec5on.
•  The
deflec5on
increases
un5l
the
Coriolis
and
pressure
gradient
forces
are
in
geostrophic
balance:
at
this
point,
the
air
flow
is
no
longer
moving
from
high
to
low
pressure,
but
instead
moves
along
an
isobar.
•  (Note
that
this
explana5on
assumes
that
the
atmosphere
starts
in
a
geostrophically
unbalanced
state
and
describes
how
such
a
state
would
evolve
into
a
balanced
flow.
In
prac5ce,
the
flow
is
nearly
always
balanced.)
•  The
geostrophic
balance
helps
to
explain
why,
in
the
northern
hemisphere,
low
pressure
systems
(or
cyclones)
spin
counterclockwise
and
high
pressure
systems
(or
an;cyclones)
spin
clockwise,
and
the
opposite
in
the
southern
hemisphere.
•  Flow
of
ocean
water
is
also
largely
geostrophic.
•  Just
as
mul5ple
weather
balloons
that
measure
pressure
as
a
func5on
of
height
in
the
atmosphere
are
used
to
map
the
atmospheric
pressure
field
and
infer
the
geostrophic
wind,
measurements
of
density
as
a
func5on
of
depth
in
the
ocean
are
used
to
infer
geostrophic
currents.
•  Satellite
al5meters
are
also
used
to
measure
sea
surface
height
anomaly,
which
permits
a
calcula5on
of
the
geostrophic
current
at
the
surface.
•  The
effect
of
fric5on,
between
the
air
and
the
land,
breaks
the
geostrophic
balance.
•  Fric5on
slows
the
flow,
lessening
the
effect
of
the
Coriolis
force.
•  As
a
result,
the
pressure
gradient
force
has
a
greater
effect
and
the
air
s5ll
moves
from
high
pressure
to
low
pressure,
though
with
great
deflec5on.
•  This
explains
why
high
pressure
system
winds
radiate
out
from
the
center
of
the
system,
while
low
pressure
systems
have
winds
that
spiral
inwards.
•  The
geostrophic
wind
neglects
fric5onal
effects,
which
is
usually
a
good
approxima5on
for
the
synop5c
scale
instantaneous
flow
in
the
midla5tude
mid‐troposphere.
•  Although
ageostrophic
terms
are
rela5vely
small,
they
are
essen5al
for
the
5me
evolu5on
of
the
flow
and
in
par5cular
are
necessary
for
the
growth
and
decay
of
storms.
•  Quasigeostrophic
and
Semigeostrophic
theory
are
used
to
model
flows
in
the
atmosphere
more
widely.
These
theories
allow
for
divergence
to
take
place
and
for
weather
systems
to
then
develop.
Cyclonic
gyres
•  In
meteorology,
a
cyclone
is
an
area
of
closed,
circular
fluid
mo5on
rota5ng
in
the
same
direc5on
as
the
Earth.
•  This
is
usually
characterized
by
inward
spiraling
winds
that
rotate
an5clockwise
in
the
Northern
Hemisphere
and
clockwise
in
the
Southern
Hemisphere
of
the
Earth.
•  Most
large‐scale
cyclonic
circula5ons
are
centered
on
areas
of
low
atmospheric
pressure.
•  The
largest
low‐pressure
systems
are
cold‐core
polar
cyclones
and
extratropical
cyclones
which
lie
on
the
synop5c
scale.
•  Warm‐core
cyclones
such
as
tropical
cyclones,
mesocyclones,
and
polar
lows
lie
within
the
smaller
mesoscale.
•  Subtropical
cyclones
are
of
intermediate
size.