A large part of the energy that drives the Ferrel cell is provided by the polar cell and Hadley cell circulating on both sides and that drag the Ferrel cell with it. A diagram with appropriate labels may help your explanation. Heat from the Earth’s core maintains the circulation of hot, fluid rock in the upper mantle, forming convection cells below the crust. Figure 3. The overall effect results in energy (or heat) from the tropics towards the poles in a gigantic conveyor belt. As that air reaches lower latitudes it is subject to more intense solar energy, warms, rises, and is drawn toward the low-pressure areas that are high above the poles. Thus, between the extreme latitudes of Hadley’s cell (±30°) and the polar cell (±60°), driven by their respective movements, appears the cell (Figure 2) discovered by the American meteorologist William Ferrel (1817-1891), which now bears his name. Synthetic representation of the global atmospheric circulation. At low viscosities, Held and Hou ( 1980 ) note the development of a small Ferrel cell at the poleward‐tilting edge of the Hadley cell. Coriolis Effect So as we have seen, the continued effect of the three circulation cells (Hadley, Ferrel, and Polar), combined with the influence of the Coriolis effect results in global atmospheric circulation. In between the Hadley and polar cells in each hemisphere is a third cell of air circulation. (b) What is the relationship between the Hadley cells north and south of the equator and the The Hadley cell is not hemispherically symmetric, instead the winter-cell is far stronger than the summer cell. The structure of the Hadley cell is not entirely determined by the tropical heating; fluctuations in the flow (often termed ‘eddies’) also play a significant role in shaping the intensity and structure of the Hadley circulation. This can be seen in Fig.3. drives this circulation. Its northern rising limb is shared with the Polar cell located between 50 degrees N to 60 degrees N and the North Pole, where cold air descends. low (Fig.1 Š bottom panel) This frictionally-induced surface ⁄ow drives a meridional circulation (a circulation in the north-south plane) Š forming the Ferrel Cell and, in part, the Hadley Cell too. This circulation creates two additional cells in the polar regions. The resulting movement of molten or semi-molten rock drives the process known as plate tectonics that is responsible for splitting the crust into continental “plates” that move relative to one another. The Ferrel cell is a thermally indirect circulation: The Ferrell cell is between 30oN and 50o to 60oN. The momentum and heat transport by eddies acts to amplify the subtropical portion of the Hadley cell. This cell shares its southern, descending side with the Hadley cell to its south. The Hadley cell is a ‘thermally direct’ circulation, meaning that rising motion is associated with relatively warmer parcels, and sinking motion with relatively cold parcels. We hypothesize that it is the interaction of convection with the Ferrel cell, rather than the Hadley cell that ultimately drives the axisymmetric Hadley cell into the upper troposphere. Thus we see that in: middle-latitudes Š low-level convergence forces ascent Š lows and CY-CLONES Š precipitation The rising air creates a circulation cell, called a Hadley Cell, in which the air rises and cools at high altitudes moves outward (towards the poles) and, eventually, descends back to the surface. (a) How do the Hadley cells drive the Trade Winds, and why do they blow from east to west?