 The dominant source is the input of heat at the surface, primarily due to evaporation.The bulk aerodynamic formula for the rate of heat input per unit area at the surface, formula_33, is given by

where formula_14 represents the enthalpy difference between the ocean surface and the overlying air.The second source is the internal sensible heat generated from frictional dissipation (equal to formula_19), which occurs near the surface within the tropical cyclone and is recycled to the system.