Internal wave signatures in the Tropical Atmosphere Ocean array from paired moorings

In order to replace obsolescent sensors in the Tropical Atmosphere Ocean (TAO) array and comply with the Ten Climate Principles, twenty-nine TAO Refresh buoys were deployed near paired TAO Legacy buoys for approximately one year each. At the end of each deployment, a statistical comparison of the daily averaged data was conducted for each pair of sensors. The results are summarized elsewhere. The subsurface ocean temperature sensor comparisons provided some unexpected results. While the average ocean temperature differences within the mixed-layer and at depth were nearly identical, average temperature differences in the thermocline were higher than expected and not within the statistical accuracy of the sensors. A comparison of the variability of the paired ocean temperature sensors and the amount of drift that occurred during each deployment led to the conclusion that the TAO Refresh sensors were reporting the same oceanographic phenomena as the TAO Legacy sensors. Closer examination of the high resolution (10-minute interval) ocean temperature data within the thermocline exhibited internal wavelike signatures. At some locations within the water column, the temperature at a single depth changes 10 Kelvins over a period of 10 minutes. Although this is an extreme example, it indicates the difficulty in comparing the data from sensors on moorings which were generally less than 5 kilometers apart. The internal wavelike signatures range from small to greater than 100 meter amplitudes. Attempts to apply a phase shift to the data to compensate for the movement of these features were unsuccessful, suggesting that the internal wave signatures were arriving from different directions at various times. These phenomena are prevalent throughout the TAO array.