Convection, Wind, and the Coriolis EffectHow uneven heating and the Earth’s rotation drive

Earth’s climate

Core Case StudyBlowing in the Wind:

A Story of Connections Wind connects

most life on earth.– Keeps tropics from

being unbearably hot.

– Prevents rest of world from freezing.

Figure 5-1

Weather & Climate

Weather is a local area’s short-term physical conditions such as temperature and precipitation.

Climate is a region’s average weather conditions over a long time.– Latitude and elevation are the major

determinants of climate.

Earth’s Current Climate Zones

Figure 5-2

How the Earth Heats Radiation -

transfer of heat energy by electromagnetic wave motion

Conduction – transfer of energy from direct molecule to molecule contact – occurs in solids

Convection – transfer of energy through moving currents – occurs in fluids (liquids & gases)

Source: Atmospheric Processes: Radiation Introduction o the Atmosphere. Retrieved on September 30, 2009 from http://www.ucar.edu/learn/1_1_2_5t.htm

Solar Energy and Global Air Circulation: Distributing Heat

Global air circulation is affected by the uneven heating of the earth’s surface by solar energy, seasonal changes in temperature and precipitation.

Figure 5-3

What is Radiation?

About 43% of the total radiant energy emitted from the sun is in the visible parts of the spectrum. The bulk of the remainder lies in the near-infrared (49%) and ultraviolet section (7%). Less than 1% of solar radiation is emitted as x-rays, gamma waves, and radio waves.

Source: Atmospheric Processes: Radiation Introduction o the Atmosphere. Retrieved on September 30, 2009 from http://www.ucar.edu/learn/1_1_2_5t.htm

What is Convection? Movement that results when heat

is transferred in a fluid First, warmed fluids (like water or

air) become less dense and will rise opposite to the force of gravity.

Next, cooler fluid will move to replace the rising warm fluid and it will be warmed itself.

This cycle repeats to mix the fluid. Convection model Julius Sumner Miller on Convection - a riot!

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Convection Currents Global air circulation

is affected by the properties of air water, and land.

Figure 5-5

Topography and Local Climate:Land Matters

Interactions between land and oceans and disruptions of airflows by mountains and cities affect local climates.

Figure 5-8

Temperature Inversions

Cold, cloudy weather in a valley surrounded by mountains can trap air pollutants (left).

Areas with sunny climate, light winds, mountains on three sides and an ocean on the other (right) are susceptible to inversions.

Figure 19-5

What on Earth?Descriptions of Earth’s Convection

Edmond Halley1656-1742

reasoned that intense solar radiation heated the air near the Equator and caused it to expand and rise up.

This rising air is replaced by cooler air converging on the Equator from the northern and southern hemispheres.

Circulation of the air is driven by a pressure-gradient force, which causes high-pressure (cooler, more dense) air to move into regions of low-pressure (warmer, less dense) air.

predicted a flow of air from the poles to the Equator where the air masses converge.

What on Earth?Descriptions of Earth’s Convection

George Hadley1685-1768

English lawyer and amateur meteorologist

First to describe the reason the equatorial trade winds preferentially blow westward.

Recognized that Earth is a rotating sphere and that sites on its surface travel with different speeds (travel different distances in equal times).

Model of Earth’s convection termed the ‘Hadley cell’ in his honor.

Convection Cells

Heat and moisture are distributed over the earth’s surface by vertical currents, which form six giant convection cells at different latitudes.

Figure 5-6

Prevailing Wind Belts on the Earth

A Horizontal View

The Coriolis Effect French mathematician, mechanical

engineer, and scientist Determined simple rules for the

direction of moving objects on the surface of a rotating sphere, now known as the Coriolis effect:– The apparent (Coriolis) force is

perpendicular to the velocity of the object and the rotation axis.

– A balance of forces causes objects traveling in the Northern Hemisphere to curve to the right.

– A balance of forces causes objects traveling in the Southern Hemisphere to curve to the left.

Gustave Gaspard de Coriolis 1792 - 1843

http://www.youtube.com/watch?v=_36MiCUS1ro

The Coriolis Effect

Visualizing the Coriolis Effect Earth rotates at different speeds at different latitudes. v = d/t

– The Coriolis Model

A

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Major Wind Belts

Prevailing Wind Belts of Earth

The earth is encircled by several broad prevailing wind belts, which are separated by narrower regions of either subsidence or ascent. The direction and location of these wind belts are determined by solar radiation and the rotation of the earth. The three primary circulation cells are known as the: Hadley cell; Ferrel cell; and Polar cell.

Coriolis Effect

Significance of Wind Belts?

Guide weather and storms

Jet Stream – 100 mph– Between 30-60º– Above friction zone

Influences Sailing & Navigation

Deserts @ 30º

Figure 5-4

Ocean Currents: Distributing Heat and Nutrients

Ocean currents influence climate by distributing heat from place to place and mixing and distributing nutrients.

Figure 5-7