Lecture 8 : Global Climates

Weather

The variation in temp., precipitation (and other atm. variables) over periods of hours to days.

Climate

The typical atm conditions that occur throughout the year, avg over many years.

Greenhouse effect

The process of solar radiation striking Earth, being converted to infrared radiation, and being absorbed and re-emitted by atm gases.

Greenhouse gases

Those that absorb and re-emit infrared radiation and contribute to the greenhouse effect.

H2O and CO2 most prevalent gases, from transpiration, decomposition, respiration, and eruptions.

Nitrous oxide (N2O), Methane (CH4), and Ozone (O3) are naturally derived — Humans can alter the amount of these gases.

Albedo

The fraction of solar energy reflected by an object

Light colored surfaces are more than dark-colored surfaces

Solar equator

The latitude where the sun is directly overhead at noon. Its position varies over the year.

Four important physical properties of the atmosphere

1. Warm air is more buoyant than cold air

2. Warm air can hold more water than cold air

3. Changes in air pressure cause a change in air temp.

4. Rotation of the earth deflects the movement of air masses.

Saturation point

The maximum amount of water vapor that air can hold at a given temp.

Adiabatic cooling

The decline in air temp. resulting from reduced pressure as air rises higher in the atm. and expands

Adiabatic heating

the increase in air temp. resulting from increased pressure as it sinks towards the ground and decreases in volume.

Hadley cells

The two circulation cells of air between the equator and 30N and 30S latitudes

Intertropical convergence zone (ITZC)

The area where the two Hadley cells converge and cause large amounts of precipitation.

Polar cells

atmric. convection currents between 60* and 90* latitudes that are similar to Hadley cells

Coriolis effect

The dif. rotation speeds deflect the direction of surface air circulation.

Northeast trade winds

Air moving along the surface of Earth w/in the northern Hadley cell is deflected so that it moves from the northeast to the southwest

Southeast Trade Winds

Air moving along the surface w/in the southern Hadley cell is deflected to the northwest

Westerlies

Winds in the mid-lat. tend to move from west to east.

Ocean currents

Warm tropical water circulates up along western reaches of ocean basins towards the poles, and cold polar water circulates down along easter reaches.

Gyres

• large-scale water circulation in the oceans

• Clockwise in the Northern Hemisphere, counterclockwise in the Southern Hemisphere.

Upwelling

• An upward movement of ocean water

• Along continents where surface currents move away from the coastline — Typically on the western coasts of continents
  

Thermohaline circulation

a global pattern of surface- and deep-water currents that flow as a result of variations in temp. and salinity that change the density of water.

Rain shadow

a region w/ dry conditions found on the leeward side of a mountain range as a result of humid winds from the ocean causing precipitation of the windward side.