Vertical Structure
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Jupiter (left) and Saturn (right)
are gaseous and so where their atmospheres begin as
well as end depends upon arbitrary definitions. The atmospheres of
Jupiter and Saturn contain tropospheres (the "weather" forming
layer) and stratospheres.
The brightly colored stripes seen on the surface of Jupiter and Saturn
are different cloud layers (ammonia ice, ammonium hydrosulfide, and
water ice). One sees to different depths (and thus
to different temperature regions) when one looks at the stripes. The ordering
of the colors is Red, White, Brown, and Blue as one moves inward toward
higher temperatures. That is, the reddish regions are the coolest, they sit
highest up in the atmospheres.
Why the stripes are the particular
colors they are is not clear however; the color depends upon chemistry
which we do not quite have a handle on.
Note that the atmosphere of Saturn is much thicker (spread-out) than is
Jupiter's -- Saturn goes a depth of 300 km compared to Jupiter that goes to
a depth of 150 km. It is this spreading-out of the atmosphere of
Saturn that gives it its more muted coloration.
ATMOSPHERIC MOTIONS
The light colored stripes are known as zones
while the darker colored
stripes are known as belts. The
thin narrow dark stripes which
separate the regions are known as bands
. Also, we cannot forget
Jupiter's Great Red Spot,
which is a large and stable (Robert Hooke discovered the Great Red Spot
in the mid 1600s) atmospheric disturbance that exhibits cyclonic motion.
The interesting patterns and motions seen in the Jovian atmospheres are
driven primarily by the large heat flow through the atmospheres (due to
flow from the interior and heating by the Sun) and by the
rapid rotation of Jupiter and Saturn.
Comment
Both Jupiter and Saturn rotate with
periods on the order of 10 hours, the Earth has a rotational period of 24
hours. The difference is more extreme than these numbers imply however.
Why?
Recall that a person standing on the equator of the Earth is carried
along by the rotation of the Earth with a speed of
speed = circumference/day = 25,000 mi/24 hr = 1,000 mi per hr
On Jupiter, a person standing at the equator is carried along at a speed of
speed = circumference/"day" = 250,000 mi/10 hr = 25,000 mi per hr
The centrifugal force
(and other "rotational" forces) play important roles on the Jovian planets.
Let's consider some effects of the heat flow coupled to the
rotation in the atmospheres of Jupiter and Saturn.
The heat flow drives motions in the atmosphere of Jupiter and Saturn.
Material heated deep in the atmosphere heats ---> it becomes less dense
and so rises (carrying heat upward). It
cools as it rises ---> it becomes denser and eventually reaches a point
where it will start to sink. It then returns
to the deeper layers where it is heated and again starts to rise. As in
the interior of the Earth, this leads to large scale motions in the
atmospheres of Jupiter and Saturn. The warmer rising stuff is light in
color while the cooler sinking stuff is brownish in color.
Because different latitudes on Jupiter and Saturn are heated by
different amounts, latitudinal motions are driven.
The equator is warmer than the poles which tends
to drive the circulation from equator poleward.
If the effects of rotation were negligible, we would simply have this up
and down (more or less vertical) motion and motion straight toward the poles.
However, rotation is not negligible
and the motion becomes more complicated. To understand what can happen,
consider something known as
angular momentum.
So, on Jupiter and Saturn, we find that the hottest material near the equator
of the planets is forced to flow toward the poles. The hot flows moving
poleward forces
some of the cooler material to circulate downward toward
the equator. Now recalling the Coriolis force, we note that the poleward
moving
material deflects in the eastward direction while the equatorward moving
material deflects in the westward direction. The preceding effects produce the
horizontal stripes which run parallel to the equator on Jupiter and Saturn.
A similar thing happens on the Earth where we get eastward winds and westward
winds at different latitudes.
Let's return to the
Great Red Spot
Imagine that there is a low pressure region in the atmosphere. Because of the
low pressure, some atmosphere is forced to flow into the low pressure region.
What happens?
In the northern hemisphere, the air circulates in the CCW sense as it flows
into a low pressure region. In the southern hemisphere the air circulate in
the CW sense as it flows into the low pressure region. If we have a high
pressure region, the opposite occurs. In the northern hemisphere, the air
circulates in the CW sense and in the southern hemisphere it circulates in the
CCW sense.
The Great Red Spot is in the southern hemisphere of Jupiter and the air
circulates
in it in the CCW sense with a period of ~ 6 days
(Is the Great Red Spot a high-pressure or
low-pressure region). It is huge, with
present dimensions 15,000 mi x 9,000 mi which is bigger than the Earth (
diameter ~ 8,000 mi). The Great Red
Spot may thus be similar to Terrestrial storms (hurricanes) although its
nature is not clearly understood.
In addition to the Great Red Spot, there are also
other storm-like structures on the Jovian planets:
White Ovals
and Brown Ovals
Brown Ovals: They tend to appear around
latitude = 20o N
Red Cloud on Saturn
There is also a Great Dark Spot on
Neptune
Jupiter (left) and Saturn (right) are gaseous and so where their atmospheres begin as well as end depends upon arbitrary definitions. The atmospheres of Jupiter and Saturn contain tropospheres (the "weather" forming layer) and stratospheres. The brightly colored stripes seen on the surface of Jupiter and Saturn are different cloud layers (ammonia ice, ammonium hydrosulfide, and water ice). One sees to different depths (and thus to different temperature regions) when one looks at the stripes. The ordering of the colors is Red, White, Brown, and Blue as one moves inward toward higher temperatures. That is, the reddish regions are the coolest, they sit highest up in the atmospheres. Why the stripes are the particular colors they are is not clear however; the color depends upon chemistry which we do not quite have a handle on.
Note that the atmosphere of Saturn is much thicker (spread-out) than is Jupiter's -- Saturn goes a depth of 300 km compared to Jupiter that goes to a depth of 150 km. It is this spreading-out of the atmosphere of Saturn that gives it its more muted coloration.
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The light colored stripes are known as zones while the darker colored stripes are known as belts. The thin narrow dark stripes which separate the regions are known as bands . Also, we cannot forget Jupiter's Great Red Spot, which is a large and stable (Robert Hooke discovered the Great Red Spot in the mid 1600s) atmospheric disturbance that exhibits cyclonic motion.
The interesting patterns and motions seen in the Jovian atmospheres are driven primarily by the large heat flow through the atmospheres (due to flow from the interior and heating by the Sun) and by the rapid rotation of Jupiter and Saturn.
Comment
-
Both Jupiter and Saturn rotate with
periods on the order of 10 hours, the Earth has a rotational period of 24
hours. The difference is more extreme than these numbers imply however.
Why?
Recall that a person standing on the equator of the Earth is carried along by the rotation of the Earth with a speed of
On Jupiter, a person standing at the equator is carried along at a speed of
The centrifugal force (and other "rotational" forces) play important roles on the Jovian planets.
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|
The heat flow drives motions in the atmosphere of Jupiter and Saturn. Material heated deep in the atmosphere heats ---> it becomes less dense and so rises (carrying heat upward). It cools as it rises ---> it becomes denser and eventually reaches a point where it will start to sink. It then returns to the deeper layers where it is heated and again starts to rise. As in the interior of the Earth, this leads to large scale motions in the atmospheres of Jupiter and Saturn. The warmer rising stuff is light in color while the cooler sinking stuff is brownish in color.Because different latitudes on Jupiter and Saturn are heated by different amounts, latitudinal motions are driven. The equator is warmer than the poles which tends to drive the circulation from equator poleward. |
Let's return to the Great Red Spot
Imagine that there is a low pressure region in the atmosphere. Because of the low pressure, some atmosphere is forced to flow into the low pressure region. What happens?
In the northern hemisphere, the air circulates in the CCW sense as it flows into a low pressure region. In the southern hemisphere the air circulate in the CW sense as it flows into the low pressure region. If we have a high pressure region, the opposite occurs. In the northern hemisphere, the air circulates in the CW sense and in the southern hemisphere it circulates in the CCW sense.
The Great Red Spot is in the southern hemisphere of Jupiter and the air circulates in it in the CCW sense with a period of ~ 6 days (Is the Great Red Spot a high-pressure or low-pressure region). It is huge, with present dimensions 15,000 mi x 9,000 mi which is bigger than the Earth ( diameter ~ 8,000 mi). The Great Red Spot may thus be similar to Terrestrial storms (hurricanes) although its nature is not clearly understood.
In addition to the Great Red Spot, there are also
other storm-like structures on the Jovian planets:
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There is also a Great Dark Spot on Neptune
