Direct Covariance Turbulent and Radiative Flux Measurements for the TPOS Array

Abstract:

A low power direct covariance flux system (DCFS) developed at WHOI is being used as the technology base for future deployment on selected TPOS buoys. It is designed to motion correct the 3-D sonic anemometer measurements; compute the fluxes, means and wave statistics onboard; and telemeter the data to shore in near real-time. The DCFS and a TAO buoy were successfully built by WHOI and PMEL for the project. The DCFS was modified to measure all of the variables necessary for direct covariance and bulk flux estimates including radiative fluxes. The enhanced buoy was deployed by NDBC near a TAO mooring on the equator at 165^oE on October 4, 2019. The DCFS successfully computed and telemetered fluxes, means and wave statistics every hour over the course of the deployment, which ended on April 21, 2020. The telemetered fluxes and means were used for research before recovery, which is an obvious advantage of real-time delivery of research-quality data. The enhanced mooring developed for this project can be considered a prototype for the Tier-2 Enhanced moorings we expect to deploy for the TPOS array. The enhancements include directly measured momentum and buoyancy fluxes, surface waves, and all variables required to compute bulk fluxes including radiative fluxes and currents, which are available in near real-time. The fluxes and waves data can be directly used in process studies to force the ocean as well as improve wind-speed and wave-based parameterization of the bulk flux algorithm used on other TPOS buoys.