The amount of solar energy reaching Earth at any particular latitude is defined by time of year and the tilt of the Earth with respect to the Sun. Use the applet below to explore how the incoming energy from the sun varies with time of year and latitude. Note that the red curve represents calculations set by the left menu bar and the black dots for the right menu bar.

  • Set the date to March 21, the vernal equinox, and the latitude to the near the South Pole (-89) for both cases, and hit the calculate button. Select and calculate a few other latitude up to the North Pole and answer the question: "How does the distribution of solar energy change as a function of latitude?"
  • Now change the date to June 21, the summer solstice, and compute the incoming solar radiation at the same latitudes. How does changing the date from March 22 to June 21 impact the distribution of solar energy?
  • Compute the incoming solar radiation for June 21 at 23N (+23), the summer solstice for the Northern Hemisphere, and December 21 at 23S (-23), the summer solstice for the Southern Hemisphere. Why is the distribution of solar energy different?

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