Autonomous Microstructure EM-APEX Floats
Technical Report,01 Jan 2009,31 Dec 2015
University of Washington - Applied Physics Laboratory Seattle United States
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Fast responding FP-07 thermistors have been incorporated on profiling EM-APEX floats to measure microscale ocean temperature fluctuations produced by turbulence. In this implementation, the FP-07 thermistor generates an electrical signal corresponding to ocean temperature fluctuations, which is conditioned by an analog circuit board, and digitized and recorded to a custom data acquisition and storage board. The raw and processed temperature observations are stored on a microSD card. Results from eight microstructure EM-APEX floats deployed in the Sargasso Sea are presented here. The slow profiling speed of EM-APEX floats enables them to capture the higher wavenumber regime of microscale temperature variation. The quality of temperature variance dissipation rates estimated from microstructure EM-APEX floats is verified by their agreement with the Batchelor spectrum and by the close inter-float agreement of temporal and vertical variations measured by multiple floats. Estimates of from the profiling floats exhibit a lognormal distribution as expected for statistically homogeneous isotropic turbulence. Turbulence measurements derived from FP-07 sensors on autonomous profiling floats are of comparable quality to those on conventional free-fall microstructure profilers.