Graduation date: 1999

Under light wind conditions, the alternation of daytime heating and nighttime cooling creates a characteristic response in the oceanic boundary layer known as the diurnal cycle. The Mellor/Yamada Level II turbulence closure model is used to analyze this response pattern. The diurnal cycle has three phases. During morning and early afternoon, radiative solar heating produces stable stratification in the upper ocean, which inhibits the vertical transport of heat and momentum. Mean current speed at the surface increases as the effects of wind stress become confined to a shallow layer. This diurnal jet produces a mixed layer in the second phase, where turbulence generated by the vertical velocity shear balances the stabilizing buoyancy flux. At night, wind mixing and convective overturning due to surface cooling rapidly deepen the surface mixed layer during the third phase. / Graduation date: 1986