1

Earth motions

•Rotates on its axis•Revolves around the Sun

Seasons—Result of constant axial tilt

Changing Sun angle •Changing Sun angle •Changing length of daylight

2

Special days Solstice—Sun's vertical rays are located at the Tropic

(23½º latitude) • June 21-22 • December 21-22

Equinox Sun’s vertical rays located at the Equator Equinox—Sun s vertical rays located at the Equator (0o latitude)• March 21-22• September 21-22

Figure 16.17Figure 16.16

3

Heat is always transferred from warmer to cooler objects

Mechanisms of heat transfer • Conduction• Convection

R di ti ( l t g ti di ti ) • Radiation (electromagnetic radiation)

Figure 16.21

Figure 16.19 Figure 16.3

Air is a mixture of gases

Major components of clean, dry air • Nitrogen (N) – 78%• Oxygen (O2) – 21%• Argon and other gases • Argon and other gases • Carbon dioxide (CO2) – 0.036% – absorbs heat

energy from Earth

Water vapor Aerosols Ozone Ozone

4

Atmospheric pressure variation

Figure 16.5

with altitude

Figure 16.7

TroposphereSt t hStratosphere

Mesosphere Thermosphere

5

Daily maximum and minimum are measuredOther values calculated from these

• Daily temperature range• Daily mean temperature • Monthly mean temperatureMonthly mean temperature• Annual mean temperature• Annual temperature range

Line of equal temperature Divides map into areas

warmer than that temperature and areas cooler than that temperatureM ith i th t t diff f Maps with isotherms use constant difference from one isotherm to the next

Often colored for ease of understanding