Geoscience Reference
In-Depth Information
EQUINOX
20 MARCH
(A)
(B)
SEPT
A´
152.1m km
147.3m km
DEC
JUNE
P´
EQUINOX
20 SEPT
PRESENT
MARCH
11,000 BP
(C)
N
Plane of the ecliptic
SPRING
W
I
NTER
SUMMER
S
Sun
Day
Night
l
AUTUMN
Figure 3.3
Perihelion shifts. A The present timing of perihelion; B The direction of its shift and the
situation at 11,000 years
BP
; C The geometry of the present seasons (Northern Hemisphere).
Source: Partly after Strahler (1965).
90°S
60°S
30°S
0°
30°N
Figure 3.4
The variations of solar radiation with
latitude and season for the whole globe, assuming
no atmosphere. This assumption explains the
abnormally high amounts of radiation received at
the poles in summer, when daylight lasts for 24
hours each day.
Source: After W. M. Davis.
60°N
90°N
90°S
60°S
30°S
Equinox
0°
Solstice
30°N
Equinox
60°N
90°N
Solstice
