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On the TOGA-COARE pilot cruise, at 147 deg E, in the western Pacific warm pool, we profiled for seventeen days at 0 deg N, and for five days at 2 deg N. Winds were generally light, and variable in direction, but rainfall was often quite intense. Contrary to what is seen in the central equatorial Pacific, we did not observe a deep diurnal cycle in dissipation extending below the mixed layer. Strong daytime restratification often prevented nightly convective deepening down to the seasonal thermocline, resulting in surface forcing remaining trapped in a shallow layer. The relaxation of horizontal density gradients into vertical appears to be an important process driving restratification. Turbulent fluxes in the bottom of the mixed layer were generally small. Following rainfall, we observed pools of fresh water, that typically disappeared within a few hours, leaving the mixed layer nearly homogeneous in salinity; thus we did not observe a permanent barrier layer. Modeling such events using the Price-Weller-Pinkle model suggests a fresh pool will be mixed away on time scales of a few days, primarily by nighttime convection. The observed vertical structure can be accounted for by local vertical mixing processes.

The Multi-Scale Profiler (MSP), a freely falling dropsonde, has been used over the last 12 years to resolve oceanic shear variance at vertical scales from a few hundred meters down to nearly a centimeter. Because MSP yielded the first complete oceanic shear spectra., it is important to document the methods by which they were produced. Large scales are measured by an electromagnetic current meter (ECM), microscales by airfoil probes, and intermediate scales by an acoustic current meter (ACM). The ACM detects velocity relative to the instrument, so the platform motion must be known to determine the water velocity. Primarily, the ACM measurements are affected by tilt oscillations and by the gross (point-mass) motion of the vehicle; the former is inferred from accelerometer data, and the latter is constructed from a model of the vehicle's response to oceanic shear. Horizontal forcing on the array of drag brushes and turning blades at the tall complicates the response by causing MSP to react strongly to fluctuations with scales near the instruments length of 4.3 m. We examine the effects of this response on spectra of the ACM measurements, noting particularly a deep notch near 0.2 cpm (cycles per meter). To account for such spectral features, the model of Hayes et al. for the TOPS dropsonde was modified so that it correctly parameterized our large tail force. We discuss the dynamics, data processing, and model formulation relevant to production of oceanic velocity profiles from the ACM data,and present analytic transfer functions-derived from Fourier transforms of the model equations-which guide selection of optimal values for the model parameters., Sponsored in part by Grant ONR-N00014-94-I-0079 and Grant URI/UW-N00014-86-K-0690.