Multi-year hourly data of air temperature, wind speed, and humidity from the TOGA TAO moored buoys over the tropical Pacific along with our derived hourly sea surface skin temperature data are analyzed to show that there are substantial diurnal variations of monthly averaged surface fluxes of latent heat, sensible heat, and momentum (e.g., one-third of the cases show monthly averaged latent heat diurnal amplitudes greater than 20 Wm-2). Daily or monthly average surface temperatures cannot provide such flux variations, suggesting that numerical modeling may require the inclusion of the diurnal variation of surface skin temperature. ¿ 1998 American Geophysical Union