Movies
A movie depicting Earth's changing orbit over the
last 100Ky. The orientation is such that spring equinox (indicated by
a vertical bar) is directly to the front with the sun behind it.
Northern Hemisphere summer is to our right, and Northern Hemisphere
winter is to the left. The apsidal (dashed) line connects perihelion
(Earth's closest approach to the sun) to aphelion (the point when
Earth is furthest from the sun). The rotaion of the apsidal line
occurs because of the precession of the equinoxes and has a roughly
twenty-two thousand year period. The semi-circle around the Earth
indicates the location of the equator and the straight line is the
polar axis. Obliquity is defined as the angle beetween the orbital
and equatorial planes. The variations in Earth's obliquity and the
eccentricity of Earth's orbit have both been increased in magnitude by
a factor of ten. Also, the Earth's angular velocity has been
decreased by a factor of five thousand. Note that Earth's angular
velocity is slowest at aphelion and fastest at perihelion.
A movie depicting the changes in insolation inensity
at the top of Earth's atmosphere over the last 400Ky. Shading
indicates the diurnally averaged insolation in Watts per meter squared
as a function of latitude and day of the year. The black triangle at
bottom indicates the location of perihelion. At left is the anomally
in annual average insolation, which varies with changes in Earth's
obliquity.
Insolation (Watts/meter^2) plotted against Age
(thousands of years before present) and Julian Day Mean annual insolation plotted against latitude and time.
Seasonal Insolation
Insolation Gradients
Insolation Movies. In order to depict spatial (latitude and
longitude) and temporal (annual and >18KY) variability,
Earth's variable orbit (74 MB, avi format)
A movie similar to the above but where the perspective is initially
one of looking down upon Earth's orbital plane and is then rotated
such that spring equinox is in the foreground with the sun behind it.
Earth's variable orbit from two
perspectives (169 MB, avi format)
Orbitally induced changes in insolation (8 MB,
avi format)
Summer energy
Summer energy is defined as the sum of the diurnal average insolation
on days exceeding a specified threshold. Plots of summer energy are
provided for the last 500 ky for various thresholds at various latitudes:
85S, 75S, 65S, 55S, 45S, 35S, 25S, 15S, 5S, 5N, 15N, 25N, 35N, 45N, 55N, 65N, 75N, 85N.
Seasonal cycle
The seasonal cycle is depicted under various orbital configurations.
Each figure has five sub-panels where the top panel shows the seasonal
cycle when Earth's obliquity is 23.3 (the average value) and Earth's
closest approach to the sun (perihelion) occurs variously during
northern hemisphere summer, fall equinox, winter, and spring equinox.
The low four panels show the seasonal cycle for each orientation of
perihelion with respect to the seasons but for an obliquity of 22.3
23.3 and 24.3 degress. A relatively large eccentricity of 0.05 is
used for all insolation figures: 85S, 75S, 65S, 55S, 45S, 35S, 25S, 15S, 5S, 5N, 15N, 25N, 35N, 45N, 55N, 65N, 75N, 85N.
Older material
for 5 degree
latitudinal increments between 90 South and 90 North.
90S 85S 80S 75S 70S 65S 60S 55S 50S 45S 40S 35S 30S 25S 20S 15S 10S 5S Equator
90N 85N 80N 75N 70N 65N 60N 55N 50N 45N 40N 35N 30N 25N 20N 15N 10N 5N
Mean Annual Insolation
January
April
July
October
Tropical Extra-tropical gradient
15 and 65 north gradient
insolation is
zonally averaged and projected onto a sphere. Each degree of longitude
roughly corresponds to a day of the year,
and both the dominant
seasonal cycle and long term orbital changes are evident. For the
equatorial view, the perspective rotates
to make all the seasons
observable.
Polar view (3 MB, mpeg format)
Equatorial view (4 MB, mpeg format)
