. . "SDN:P07::CFV8N77" . "1" . "false" . . "sea_surface_wind_wave_mean_period_from_variance_spectral_density_inverse_frequency_moment"@en . . "SDN:P07::CFV8N77" . . . "SDN:P07::CFV8N77" . "The wind wave directional spectrum can be written as a five dimensional function S(t,x,y,f,theta) where t is time, x and y are horizontal coordinates (such as longitude and latitude), f is frequency and theta is direction. S can be integrated over direction to give S1= integral(S dtheta). Frequency moments, M(n) of S1 can then be calculated as follows: M(n) = integral(S1 f^n df), where f^n is f to the power of n. The inverse wave period, T(m-1), is calculated as the ratio M(-1)/M(0)."@en . "2008-04-15 14:00:00.0" . . . . "accepted"@en . "2008-04-15 14:00:00.0" . "1" . . "" . .