Summer Solstice in the Southern Hemisphere

December 21, 2017


Meteosat Image Acquired by Europe's Meteorological Satellite Organization (EUMETSAT).
Summary Author: Jim Foster

Shown above is a full disk, visible image of the Earth as captured by the Meteosat satellite on December 18, 2017, at 1200 Z (noon). Positioned in geostationary orbit some 22,000 miles (35,400 km) above the equator, the Meteosat series of satellites permits early detection of impending tropical storms, including hurricanes and cyclones. Meteosat 9 (featured here) operates over Africa.

When the Sun is directly overhead of the Tropic Capricorn (-23.4 degrees south latitude) on December 21, it's the start of the winter season in the Northern Hemisphere, while summer is about to get underway in the Southern Hemisphere. On this date, for areas south of the Antarctic Circle (approximately 66.5 degrees south latitude) the Sun never sets, however, at the other end of the globe (66.5 degrees north latitude), the Sun is completely below the horizon. Note that at the South Pole, the Sun will be above the horizon 24 hours a day until the autumnal equinox (for the Southern Hemisphere), which in 2018 occurs on March 20.

Desert areas are easy to pick out on this image. As a result of atmospheric subsidence, the Sahara Desert and the Arabian Desert are nearly cloudless. The band of clouds stretching from near Madagascar on the far right of the image, across the Atlantic Ocean and toward northern South America at far left is known as the Inter Tropical Convergence Zone (ITCZ). This zone of low pressure and convective storms forms where the trade winds of the Northern and Southern Hemispheres come together.