In contrast, the hours of daylight change at each point in the Northern Hemisphere from a maximum during the Summer solstice to a minimum on December 21 when the Sun is directly overhead at the Tropic of Capricorn. Day and night are split equally during the equinoxes. The length of each day increases traveling northward during Summer in the Northern Hemisphere and decreases southward in the Southern Hemisphere. This pattern is reversed during the Winter solstice when the South Pole is illuminated for 24 hours and the North Pole is in darkness. The situation is reversed south of the Antarctic Circle.
Solar radiation strikes the earth more directly at the equator and tropics than in polar regions.
More heat is therefore transferred to the earth in the tropics than at the poles. Global atmospheric circulation patterns represent the planet's attempt to move warm air toward the poles and cold air toward the equatorial region. These patterns are complicated by Earth's rotation, dividing into three large convection cells in the Northern and Southern Hemispheres that control climate patterns. Global temperature and precipitation patterns are directly related to global atmospheric circulation patterns and differentiate climate regions across the globe. Areas with consistent climates are grouped together in climate regions .