Note 1 to entry: It is numerically equivalent to the period of a monochromatic wave in deep water with wave elevation variance and energy flux equal to a polychromatic sea state.

Note 2 to entry: In accordance with International Association for Hydraulic Research (International Association for Hydraulic Research (IAHR), working group on wave generation and analysis, 1989, List of sea state parameters, Journal of Waterway, Port, Coastal and Ocean Engineering 115 (6), 793–808) the spectral estimate of the energy period is preferred.

${\displaystyle T_{\text{e}}=\frac{m_{-1}}{m_0}}$, where m₋₁ and m₀ are the minus-one and zero spectral moments.