BIOL208 Lecture Notes - Lecture 3: Northern Hemisphere, Norther, Coriolis Force
10 Oct 2018
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September 12, 2018
Lecture 4 “Life on Land”
Large-Scale Patterns of Climatic Variation
• Uneven heating of the earth’s spherical surface by the sun and the tilt of the earth on its axis combine
to produce predictable latitudinal variation in climate.
• ecology was defined as the study of the relationships between organisms and their environment.
o understanding geographic and seasonal variations in temperature and precipitation is
fundamental to studying ecology. Several attributes of climate vary predictably over the
earth.
Temperature, Precipitation, and Atmosphere Circulation
• Much of the earth’s climatic variation is caused by uneven heating of its surface by the sun.
• This uneven heating results from the spherical shape of the earth and the angle at which the earth
rotates on its axis as it orbits the sun.
o Because the earth is a sphere, the sun’s rays are most concentrated where the sun is directly
overhead.
• the latitude at which the sun is directly overhead changes with the seasons. This seasonal change
occurs because the earth’s axis of rotation is not perpendicular to its plane of orbit about the sun but
is tilted approximately 23.5° away from the perpendicular
• Tilted angle of rotation is maintained throughout earth’s orbit about the sun
o the amount of solar energy received by the Northern and Southern Hemispheres changes
seasonally
• During the northern summer, the Norther Hemisphere is tilted toward the sun and receives more
solar energy than the Southern Hemisphere
o During the northern summer solstice on approximately June 21, the sun is directly overhead
at the tropic of Cancer, at 23.5° N latitude.
o During the northern winter solstice, on approximately December 21, the sun is directly
overhead at the tropic of Capricorn, at 23.5° S latitude.
• During the northern winter, the Northern Hemisphere is tilted away from the sun and the Southern
Hemisphere receives more solar energy.
o The sun is directly overhead at the equator during the spring and autumnal equinoxes, on
approximately March 21 and September 23.
o This regular shift in the latitude at which the sun is directly overhead drives the changes we
associate with the different seasons of the year.
Document Summary
Several attributes of climate vary predictably over the earth. Temperature, precipitation, and atmosphere circulation: mu(cid:272)h of the earth"s (cid:272)li(cid:373)ati(cid:272) (cid:448)ariatio(cid:374) is (cid:272)aused (cid:271)(cid:455) u(cid:374)e(cid:448)e(cid:374) heati(cid:374)g of its surfa(cid:272)e (cid:271)(cid:455) the su(cid:374). This uneven heating results from the spherical shape of the earth and the angle at which the earth rotates on its axis as it orbits the sun. Be(cid:272)ause the earth is a sphere, the su(cid:374)"s ra(cid:455)s are (cid:373)ost (cid:272)o(cid:374)(cid:272)e(cid:374)trated (cid:449)here the su(cid:374) is dire(cid:272)tl(cid:455) overhead. the latitude at which the sun is directly overhead changes with the seasons. This seasonal change o(cid:272)(cid:272)urs (cid:271)e(cid:272)ause the earth"s a(cid:454)is of rotatio(cid:374) is (cid:374)ot perpe(cid:374)di(cid:272)ular to its pla(cid:374)e of or(cid:271)it a(cid:271)out the su(cid:374) (cid:271)ut is tilted approximately 23. 5 away from the perpendicular. During the northern winter, the northern hemisphere is tilted away from the sun and the southern. In both northern and southern hemispheres, seasonal shifts in input of solar energy produces: winter= low average temperature and shorter days length.
