Objective mapping of density and acoustic Doppler current profiler velocity data. Azores Front: potential density and geostrophic velocity at 68 m in February, 1992. Source: From Rudnick (1996).

Spectral aliasing. Frequency spectral density of satellite altimetric sea-surface height. The small sharp peak at 60 days is an alias of the semi-diurnal tide. Source: From Stammer and Wunsch (1999).

The six principal empirical orthogonal functions describing the sea level pressure anomalies in the North Pacific. ©American Meteorological Society. Reprinted with permission. Source: From Davis (1976).