Earth's Orbit & Solar Energy Collection

How is our primary energy source collected and distributed in Earth & its atmosphere? This is a fundamental question which must be adequately answered before we proceed regarding specific meteorological study topics. Because Earth's rotation axis is not greatly sloped from its orbital plane and its rotation period relatively small, latitude determines weather & climate more so than longitude. Naturally defined latitudes include the Equator, Tropics of Cancer & Capricorn, Arctic and Antarctic Circles, and North and South Poles :

Why is 23.44° (& its complement 66.56°) special ? Because such is Earth's axis tilt relative with its orbital plane (ecliptic) :

Maximum poleward extent of the subsolar point determines Tropics of Cancer (North) and Capricorn (South), named for stellar constellations which our sun is seen among during the solstices :

(In the above diagram TC can be the Tropic of Cancer or Capricorn, etc.; as North & South Poles (NP & SP) define.)

Thus, the subsolar point varies during a year between 23.44° N & S :

This is called solar declination, defined positive for northern latitudes and negative for southern ones. Because axis tilt is presently decreasing (mentioned last week), the Tropics are moving equatorward - about 16 m/year. Likewise, the Arctic & Antarctic Circles are moving poleward the same amount.

As illustrated above, Earth is significantly closer to Sun during Northern Hemisphere Winter than Summer, and slightly closer during March than September Equinox :

Greatest difference being at perihelion (about 3 January) and aphelion (about 5 July) :

You may notice that solar declination changes slowly near solstices and abruptly near equinoxes, and Sun-Earth distance does more so (not only because it is illustrated with greater amplitude). Both these factors very significantly affect annual solar energy collection (solar energy varies inversely squared with distance from Sun), as energy amounts reaching our atmosphere (extraterrestrial) at solar noon illustrate :

Maximum solar energy flux (normal to solar beam) variation is quite significant, between 1422 W/m2 at perihelion to 1330 W/m2 at aphelion, a 6.7 % annual change. Peak solar energy amount (incident to horizontal) at 40 °N at June Solstice is much less than that at 40 °S at December Solstice, but the reverse is true for minimum amounts at opposite solstices. Such values are for one time of day though. Considering an entire day, most solar energy reaches the South Pole at December Solstice than at any other time and location because day length increases poleward during Summer : 

                 LAT           DD

                  0           12:06
                  5           12:23
                 10           12:41
                 15           12:59
                 20           13:19
                 25           13:40
                 30           14:03
                 35           14:29
                 40           14:59
                 45           15:34
                 50           16:19
                 55           17:19
                 58           18:06
                 60           18:47
                 62           19:38
                 63           20:11
                 64           20:51
                 65           21:47
                65.5          22:29
                65.7          22:53
                65.9          23:34
               >= 66          24:00

   Daytime duration (DD, hr:min) at various latitudes (LAT, °S)
   during 22 December 1995 (day of solstice).  24 hour day is
   less than 66.56° latitude because of atmospheric refraction.

But because atmospheric transmittance is minimal at such oblique angles :

most solar energy is collected near ground at subtropical locations (just poleward of the Tropics) during Summer Solstice, such as the Central Australian Desert.