Definition - What does Hadley Cells mean?
Hadley cells are repeating patters where the earth's atmosphere circulates due to changes in temperature and location in relation to the earth. Due to the heat near the earth's equator, warm air rises near the equator, then cools as it travels toward the northern and southern poles at high altitude and descends. It then warms as it moves toward the equator.
Safeopedia explains Hadley Cells
Hadley cells are among three separate types of atmosphere cycles, which also include Ferrel cells and Polar cells, and these, along with Hadley cells, divide the earth's troposphere into separate cells. This is because present-day atmospheric circumstances prevent heat from travelling directly from the equator to the poles. The same circulations happen on other planets, and are also explained with the same terms.