Solar radiation varies on a diurnal cycle, and therefore so do all the climate variables that it forces, including sea surface temperature (SST), wind, and in turn mixed-layer depth and upper-ocean heat storage. Satellite scatterometer data from the QuikSCAT and ADEOS-2 tandem mission have been used to estimate the amplitude and phasing of diurnal wind variations on a global basis. Statistically significant diurnal wind variations occur along coastlines all over the world, where they are commonly thought of as the land/sea breeze. Open ocean winds also undergo substantial diurnal variability at latitudes equatorward of 30 degrees latitude. The phasing of diurnal winds varies with distance from the shore. Upper ocean temperatures measured from profiling Argo floats are compared with microwave SSTs from the Advanced Microwave Scanning Radiometer for the Earth Observing System (AMSR-E) to estimate the amplitude and phasing of the diurnal cycle in upper ocean temperature. Differences between Argo and AMSR-E measurements imply that the diurnal cycle has an amplitude that decreases with increasing latitude, from about 0.1C near the equator to 0.02C near 60N/S. Maximum upper ocean temperatures occur around 18:00 local time at most latitudes. If only temperature or only wind underwent a diurnal cycle, then over the course of the day, the variations would average to zero, and we would expect no net impact on climate. Since the two processes both vary, with different phasings, they are expected to have a combined (rectified) effect on the mixed-layer, and this effect is evaluated.