Term: sea_surface_swell_wave_directional_spread

Unit: degree

Unit ref: UAAA

AMIP:

GRIB:

The quantity with standard name sea_surface_swell_wave_directional_spread is the directional width of the swell wave component of a sea. Swell waves are waves on the ocean surface and are the low frequency portion of a bimodal wave frequency spectrum. Directional spread is the (one-sided) directional width within a given sub-domain of the wave directional spectrum, 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. For a given mean wave (beam) direction the quantity approximates half the root mean square width about the beam axis, as derived either directly from circular moments or via the Fourier components of the wave directional spectrum.