Transcript Coriolis Effect

The atmosphere is very thin
The Atmosphere
Troposphere
Earth radius 6,370 km (3,981 miles)
The atmosphere extends upward to 500 km (321 miles),
HOWEVER, 99% of all atmosphere gasses are below 32 km (20 miles)
Therefore
Although the entire atmosphere = 8% of earth’s solid radius
99% of gasses 0.005 = 0.5% (one half of one percent) of earth’s radius
Cloud charts, radiosonde. instruments
For Wet Air add water vapor
(up to 7% in moist hot tropics)
4% is more typical around here.
Dry Air
Two common gasses, N2 (78%) and O2 (21%), make up 99% of dry
air. Other gasses, e.g. CO2 CH4 NO2 and water vapor H2O also play
an important role by keeping the atmosphere warm, the
“greenhouse effect”.
Solar Heating
• The equator receives 2.5 times more sunlight
(insolation [photons / m2 ]), incoming solar radiation,
than the poles.
• Highest average annual ocean surface temperatures
(~27oC) at equator
• Lowest 0oC at
high latitudes
• Diff. drives density/pressure
Differences => wind
DEMO flashlight and
globe
23.5
P = rRT
Density falls off with altitude; pressure is caused by impacts, dense air has more impacts
Pressure differences cause WIND
Winds flowing into low pressure = low density areas are said to
Flow in response to the Pressure Gradient Force.
Heat vs. Temperature
• Atoms in air are in constant motion, the energy of their
motion is known as kinetic energy. Kinetic energy
increases as the speed of atomic motion increases. Ek =
1/2mv2
(identify symbols)
• Heat energy is the total kinetic energy of all the atoms in
a substance. The more atoms present, the greater the
heat.
• Temperature represents the average kinetic energy of
the atoms in a substance. A few atoms with rapid motion
will have a higher temperature than many atoms with
slow motion.
1. Atmosphere Layers w/ Pauses
3. Tropopause
higher at equator
2. Pressure the weight of air above
Ozone layer
equator
poles
4. 75% of gasses
In Troposphere
6. Note change of sign of lapse rate at Tropopause (next slide)
5. lapse rate
6.5oC/km
Coriolis Effect
Air masses at rest above
the equator are moving
much faster than air
masses at rest over us in
NJ.
Both must rotate once per
day, but the equatorial air
goes much further.
Equatorial Air has faster spin
it still has it , so it is
As it moves toward poles
faster than land below
Coriolis Effect: Flowing winds appear to turn due to earth’s rotation
Coriolis Effect
Air in Northern Hemisphere
deflects to the right, reverse in Southern H.
DEMO: Coriolis Clip
Earth’s rotation appears to turn winds flowing along a pressure gradient
Winds blowing parallel to isobars are called geostrophic winds
This occurs well above the surface where there is no friction
Notice pressure gradient force always from high to low pressure, but Coriolis perpendicular to
actual flow direction
Coriolis “turns” them
LOW
HIGH
Polar Cell
Ferrel Cell
Hadley Cell
LOW
The major wind cells
If Earth did not rotate, there would be one cell in each
hemisphere. Note the formation of Ocean Current Gyres
Horizontal temperature differences
Temperature effects density and pressure:
P = r R’ T so T = P /r R’
If you heat something it expands and gets less dense
A 500 millibar pressure level is much higher in hot air.
Hotter air has lower density and greater volume
500 mb
700 mb
850 mb
Warm
1000 mb
Cold
Psurface
Polar Jet Formation
Steep gradients
of Pressure cause
higher velocity
geostrophic
winds.
This is the trigger
for jet stream
flow.
More polar air
is denser, so it
wedges under
the low
density warm
air. Rotation
causes an
eddy to form
For the Polar Jet, the eddy is in
the Ferrel cell on the upper
polar side, and so air flows
from the west to the east, the
“Westerlies”
Since the pressure difference is
great at the boundary, the jet is
a very fast wind
Subtropical Deserts +/- 30o latitude
Highs where Hadley/Ferrel Cells descend
Highs where Hadley/Ferrel Cells descend
“water vapor”
Water only compound in three states (liquid, gas, solid) on Earth’s surface.
Heat energy is transferred through the atmosphere as water changes from
one state to another.
The atmosphere’s heat is absorbed by water in
processes such as melting, sublimation, and
evaporation.
Evaporation puts moisture (water vapor
Condensation releases heat to air &
gas) into the atmosphere and cools the air
forms cloud droplets
“
“
These two transfer the
most energy, are less
common, don’t cause
Lifting a moist air mass results in condensation, liquid droplets are
clouds, coalescence yields precipitation
Figure 1-4b
Orographic Lifting
Windward Rain Forest Leeward Rain-Shadow Desert
Rain also on the high Leeward drainage sometimes
Flash floods on dry plateau
Ocean-Current Desert
Also Interior and Polar Deserts
Frontal Lifting
•Frontal lifting occurs when two large air masses of
contrasting density (temperature, moisture content) meet.
•The boundary between the air masses is termed a front and
may be 10 to 150 km (6-94 miles) across and hundreds of
kilometers in length.
http://www.met.tamu.edu/cl
ass/Metr304/Dirsurface/surface.html~
cP
mT
AT THE SURFACE
Friction turns surface winds back toward the pressure gradient.
Near the surface, winds almost move from High to Low pressure
They spiral counterclockwise into a Low in Northern Hemisphere
Buoyancy Lifting
(heated atoms
speed up
paddle board
analogy)
Start
density area
density floor
Local Heat
Hot Air Expands
Dense air falls into low
hot molecules bounce off the high
Atoms close together (dense, high pressure)
“fall
into” the
bounce
up nearly empty (low pressure) ar
Define Lapse Rate
Figure 1-4a
Latent Heat of Condensation
Figure 1-3c
Hurricanes
Table 1-3
Hurricanes &Typhoons
(Tropical Cyclones)
When extremely hot ocean surface
temperatures (>26oC) cause hot, moist surface
air, huge clusters of thunderstorms develop at
sea. If uplift gets extreme, these can organize
into a gigantic Low with spiral storm lines, and
winds exceeding 74 mph, a
Tropical Cyclone, aka Hurricane
Hurricanes are fueled by Latent Heat of Condensation release.
One day equals the energy production of US for a year
Jeanne
Hurricanes need hot
moist air as fuel. This is
why they weaken over
land
Trapped in
House, swept
away
Storm Surge
Storm Surge
Freshwater (rain)
floods cause most
fatalities