Since OISST starts from 1982, the base period is chosen from 1982 to 2004. Monthly climatology is derived by averaging the pentad climatology, while the pentad climatology is derived by taking the pentad mean over 1982-2004 and retaining first three harmonics. The tropical cyclone heat potential is defined as the total heat content above the 26C isotherm. The mixed layer depth is defined as the depth where the temperature deviation from the surface temperature is less than 0.8C.