*
4/23/12
* Crust
* Mantle
* Outer Core
* Inner Core
*
*The gases surrounding the
earth.
*
* Coriolis effect
* Ekman’s spiral = top down drag.
* Wind blowing over the ocean can move it due to
frictional drag.
* Waves create necessary roughness for wind to
couple with water.
* One “rule of thumb” holds that wind blowing for
12 hrs at 100 cm per sec will produce a 2 cm per
sec current (about 2% of the wind speed)
*
*
*The French scientist,
Gaspard Coriolis, first
explained the
deflection of objects
moving over the
surface due to Earth’s
rotation.
http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/fw/crls.rxml
*
Nansen and others
exploring the Arctic
noticed that ice and
surface currents move
at an angle to the wind
direction. Ekman first
explained the
mathematics of this
phenomena, and why
it decreases with
http://www.humboldt.edu/~gdg1/Spiral.htmldepth to produce the
spiral pattern.
General Surface Current Patterns
http://earth.usc.edu/~stott/Catalina/Oceans.html
*
*Circular pattern of wind
and surface current
motion
*Prevailing Westerlies
and Trade Winds
strongly influence these
flows
*Clockwise rotation in the
Northern Hemisphere,
counterclockwise in the
Southern
http://earth.usc.edu/~stott/Catalina/Oceans.html
*
*Unifying concept: “Global Ocean Conveyor Belt”
http://seis.natsci.csulb.edu/rbehl/ConvBelt.htm
*
* Surface Currents Transport Heat from the Equator to the Poles
* May serve as “heat sources” to cooler overlying air, “heat
sinks” from warmer
* Evaporation and condensation participate in latent heat
exchanges
* Surface Currents transport gases, nutrients and
pollution
* O2 and CO2
* Nutrients (upwelling and downwelling)
* Pollution dispersal
* Impact on fisheries and other resources
*
* Wind-driven currents occur in the uppermost
100 m or less
* Density differences causes by salinity and
temperature produce very slow flows in deeper
waters.
* polar regions radiate away more heat energy
than they receive from the Sun in the course of a
year. However, they are prevented from
becoming progressively colder each year
primarily by the transport of heat through the
atmosphere and the oceans.
*
Land and Sea Breezes
Temperature contrasts (the result of the
differential heating properties of land and
water) are responsible for the formation of
land and sea breezes.
Mountain and Valley Breezes
Similar to the land and sea breeze in its diurnal (daily) cycle
-Valley breezes occur in the day because air along mountain slopes is
heated more intensely than air at the same elevation over a valley
floor.
-Rapid radiational heat loss in the evening reverses the process to
produce a mountain breeze.
Chinook (Foehn) Winds
Caused by pressure systems on the leeward (back) side of mountains
which pull air over the mountains. As the air descends it is heated
adiabatically.
Warm, dry winds sometimes move down the slopes of the Rockies,
where they are called Chinooks, and the Alps they are called foehns.
These naturally occurring winds can be very harmful to human
activities.
Katabatic (Fall)Winds
Cold air over highland areas is set in motion, gravity causes the
air to rush over the edge of the highland like a waterfall.
Katabatic winds are generally much stronger than a mountain
breeze. There must be a strong temperature gradient with the
colder air aloft.
Diagram of Katabatic Winds
Some Katabatic Winds
•mistral
•bora
•Antarctica is the
windiest place on
earth. Wind speeds
of 300 kilometres
Weather
* Minutes to months
* Temp, precipitation,
cloudiness, pressure,
wind, visibility
* What you get
Climate
* The average of
weather over time and
space
* How the atmosphere
behaves over a long
period of time
* What you expect
*Weather vs. Climate
 Earth’s Motions
• Earth has two principal motions—rotation and revolution.
 Earth’s Orientation
• Seasonal changes occur because Earth’s position relative to the
sun continually changes as it travels along its orbit.
*Earth-Sun
Relationships
*
Tilt of the earth’s axis = variation in
seasons.
In the Summer = the northern hemisphere gets more direct sunlight,
so there is more photosynthetic light reactions, which take in carbon
dioxide. Therefore, there is LESS carbon dioxide in the atmosphere
during the summer.
*Daily Paths of the Sun
at 40° N latitude—June
Figure 11.9 A
In the winter = the northern hemisphere receives less direct sunlight, so
there is less photosynthetic light reactions occurring due to less light.
Therefore, in the winter and fall in the northern hemisphere have MORE
carbon dioxide.
*Daily paths of the Sun
at
40° N latitude—
Figure 11.9 B
December
*Relationship of Sun Angle and
Intensity of Solar Radiation
***Seasonal variations in photosynthetic activity= changes in carbon dioxide
levels***
Figure 11.10
Single-Cell Circulation Model: Hadley Cells
George Hadley, in 1735, proposed that temperature contrast
between the poles and the equator creates a large convection
cell in each hemisphere.
Global circulation on a
nonrotating Earth. A
simple convection system
is produced by unequal
heating of the atmosphere
on a nonrotating Earth.
Three-Cell Circulation Model
In the 1920’s a three-cell circulation model (for each hemisphere)
was proposed.
Features of the
circulation pattern:
•horse latitude
•trade winds
•doldrums
•prevailing westerlies
•polar easterlies
•polar front
Observed Distribution of Pressure and Winds
An imaginary uniform Earth
with idealized zonal
(continuous) pressure belts
*
4/25/12-4/26/12
* Atmospheric Density
* Density or ppm measure the concentration of gases.
* Density = Mass/Volume
(units of kg/m3)
* At surface, 1.2 kg of air per cubic metre.
* Concentration
= parts per million (ppm)
* Air is compressible.
* Gas molecules are not attached to each other, and resist being
squeezed closer together.
* Because of compression from the weight of overlying air, the
atmosphere is denser near the surface than above.
* The force or mass per unit area of a column of
air.
*
Due to compressibility,
atmospheric mass
gradually “thins out”
with height.
less overlying
weight
* Pressure and Density
more overlying
weight
Vertical Pressure Profile
Pressure always decreases with
height.
Pressure at surface = 1000 mb
Pressure at 18 km = 100 mb
100 mb / 1000 mb = 10% above 18 km
or 90 % below 18km
Pressure at surface = 1000 mb
Pressure at 5.5 km = 500 mb
500 mb / 1000 mb = 50% above 5.5 km
Vertical Structure of the Atmosphere
Thermal Layers of the Atmosphere
Four distinct layers of the
atmosphere emerge from
identifiable temperature
characteristics with height
Vertical Structure of the Atmosphere
Troposphere
The lowest layer, named as this region
promotes atmospheric overturning
Layer of virtually all weather
processes
Warmed at the surface by solar
radiation
Identified by a steady temperature
decrease with height
Thinnest layer, but contains 80% of
the mass
Due to thermal expansion, the
tropopause is roughly 16 km over the
tropics, but only 8 km at poles
Vertical Structure of the Atmosphere
Updraft has “overshot” the tropopause and
entered the lower stratosphere
Flattened Anvil cloud top reveals
the top of troposphere
Vertical Structure of the Atmosphere
Stratosphere
Area of little weather (“stratified”)
A layer where temperature increases with
height
Inversion caused by the absorption of
ultraviolet radiation by ozone
Although the ozone layer exists through an
altitude between 20-30 km (12-18 mi),
actual concentration of ozone can be as
low as 10 ppm
Vertical Structure of the Atmosphere
Mesosphere and Thermosphere
Combined the two layers account for only
0.1% of total atmospheric mass
Mesosphere, which extends to about 80
km (50 mi) is characterized by decreasing
temperatures with height and is the coldest
atmospheric layer
The upper most layer; slowly merges with
interplanetary space and is characterized
by increasing temperatures with height
Temperatures approach 1500oC, however,
this only measures molecular kinetic
energy as the sparse amount of mass
precludes actual heat content
*
* Nitrogen - 78.084%
Oxygen - 20.95%
Argon - 0.934%
Carbon Dioxide - 0.036%
Neon - 0.0018%
Helium - 0.0005%
Methane - 0.00017%
Hydrogen - 0.00005%
Nitrous Oxide - 0.00003%
Ozone - 0.000004%
* Water = 1-4% usually when
air is wet
*
*
* Any atmospheric gas that effects the
atmosphere by absorbing the infra-red
radiation that is reflected off the surface of
the earth.
* Carbon dioxide (CO2)
* Nitrous oxides (N2O)
* Methane (CH4)
* CFC’s (chlorinated flourohydrocarbons)
*
*
* Ozone = O3
* Ozone in the troposphere (ground level)= bad
* Due mostly to motor vehicles
* Strong oxidant
* Respiratory irritant
* Ozone in the stratosphere = good
* Absorbs harmful Ultraviolet radiation (UV-C and UV-B)
that cause Basal cell carcinoma (most common) and
melanoma (deadliest).
* We are “burning a hole” in the ozone layer in the
stratosphere with CFC’s (reduced by Montreal Protocol)