I ATMOSPHERE
The earth's outer layer is fluid

• consists of the ocean and atmosphere
• The heating of these fluids, and the transfer of heat and water vapor, lead to weather and climate.
• Climate is weather averaged over many years

STRUCTURE OF THE ATMOSPHERE

There is great vertical movements in the troposphere, where our weather occurs.

Above the troposphere, separated by the

TROPOPAUSE...... there is the STRATOSPHERE.

• This contains the ozone (03) layer.
• There is much less vertical mixing in the stratosphere.
• The tropopause acts as a barrier preventing easy

--- Thus material injected into the stratosphere is not easily removed into the troposphere.

• Above this is the MESOSPHERE

 

COMPOSITION OF THE ATMOSPHERE

(N2) and Oxygen (02).

Other components include Argon (Ar), Carbon dioxide (CO2), Methane (CH4), Ozone (03), and Water Vapor.

• C02 and CH4 are important GREENHOUSE GASES- they allow the sun's UV and visible light to penetrate the earth's air and reach the surface. However, they absorb some of the long-wave radiation emitted from the Earth's warm surface. These gases therefore act to "blanket" the earth in that the earth is warmer than it would otherwise be

- in the stratosphere, it shields the earth's

surface from damaging solar UV radiation.

• Water Vapor

- evaporation removes energy from water; water vapor carries this energy (Latent Heat) away.

- Condensation of the water vapor releases energy. example: HURRICANES' power derives from condensing water vapor within rising air in the eye.
 
 

HEAT BUDGET

Solar Heating

• The Earth does not heat up because there is an equilibrium between incoming and outgoing radiation.

is balanced by re-radiation of heat from the earth (infrared) to space.

-- Green house gases cause this process to occur at higher temperatures.

WINDS

• Driven by unequal heating of the Earth's surface

--high latitude vs. low latitude

UNEQUAL HEATING CAUSES CONVECTION CELLS

WARM, MOIST (LESS DENSE) AIR RISES, THEN COOLS AND SINKS---

THE RETURN, SURFACE FLOW ARE THE SURFACE WINDS

This is complicated by the Earth's rotation, which gives

rise to a force called the

CORIOLIS EFFECT

This causes moving objects to be deflected:

• to the right, in the northern hemisphere
• to the left, in the southern hemisphere
• it is greatest at the poles, absent at the equator

TO AN OBSERVER STANDING ON THE ROTATING DISK, AN OBJECT IS APPARENTLY DEFLECTED TO THE RIGHT AS THE DISK ROTATES UNDER THE OBJECT

THE INTENDED TARGET "X" IS ROTATED WITH THE DISK. THEREFORE IT SEEMS THAI' PROJECTED OBJECT 'D "MISSES" TO THE RIGHT!!!!

The next two viewgraphs illustrate how low and high pressure areas lead to winds

1) There are global high and low pressure areas which dictate the general flow of the winds and climate.

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2) There are also regional, or local, low and high pressure systems coresponding to divergence and convergence of air.

Hurricanes are intense low pressure systems, where air rushes in and rises, releasing enormous amounts of energy:

• derive power from condensation of water vapor (latent heat)

 
 
• can't form near the equator (there is only small Coriolis force at equator)--- they won't spin!!

 
 
• Hurricanes die over land or cold water, as there is no energy source (i.e. water vapor)

Temperature

• Largely determined by latitude., Solar heating most direct at the equator (low latitudes) and least direct at higher latitudes (toward the poles).
• Currents act to redistribute heat.

Salinity

• Salinities controlled by

precipitation (E-P).

- S is large in the central subtropical gyres, where there is less rainfall and strong prevailing winds.

• the proximity to river runoff.

• the proximity to ice meltwater.

Highest salinities occur where there is an excess of evaporation over precipitation. Lowest salinities occur where there is an excess of precipitation, and where there are inputs of river and melt water.

The distribution of water and heat are related through the heat stored in water and in water vapor.

To understand these distributions, it is useful to construct budgets. In budgets,

SUM of INPUTS = SUM of OUTPUTS

1) WATER BUDGET

Precipitation + runoff + current transport + meltwater

= evaporation + current transport

2) HEAT BUDGET

Heat from sun + heat carried in from currents =

latent heat lost from evaporation

+ longwave radiation

+ heat lost to the atmosphere

+ heat carried away by currents

BOX MODELS

• a simple way to illustrate budget

The system is at steady state, in that the volume of the basin does not change..... there is a balance of inputs and outputs.

STRUCTURE OF THE OCEAN

• The ocean is density stratified
• There are 3 main vertical zones:
• - 50 to 200 m thick

• pycnocline

- thermocline

- halocline

- acts as a barrier between the surface and deeper water.

• deep layer

- it's T,S not very variable. It's

characteristics fixed in polar regions

Temperature - Salinity Diagrams

• The T and S of deep waters are fixed at the surface.

 
 
• Once formed, the T,S of the deep waters don't change ---- these properties are conservative.

 
 

Therefore, T and S can be used to trace the mixing of different water masses.

CURRENTS

• large scale water movements

 
 
• like wind, currents are driven by unequal heating of the earth's surface.

 
 
• Currents tend to redistribute heat from the tropics to the poles.

 
 
• Numerous forces tend to affect the movement of water:

 
 
• wind
• gravity
• friction
• Coriolis force

A) Open Ocean

• Driven primarily by the wind

• GYRES

- bounded by westward flowing

equatorial currents and eastward flowing high latitude currents.

The affect of wind upon the water is complicated by the earth's rotation, which is called the Coriolis Force.

• The wind imparts momentum to the ocean surface, which drags the water beneath

• Coriolis Force - deflects the water movement to the right, in the Northern Hemisphere.

 
 
• This motion is propagated downwards as a spiral.

The relationship between the wind, earth's rotation and the surface ocean leads to a net transport which is 90' to the right of the wind.

Leads to convergence in gyres

GEOSTROPHIC FLOW

• Water responds to sloping water surface by running downhill. But this too is affected by the Coriolis Force.

 
 
• The force of GRAVITY is balanced by the CORIOLIS force, such that the current velocity is parallel to the slope