ESRL/PSD Seminar Series

Understanding the transfer of energy in the oceans from the largest, basin scales to the smallest, dissipation scales is vital to balancing the Earth's energy budget. Without direct velocity measurements at all depths, the Argo profiling float network and its global temperature and salinity measurements down to 2000m provide the possibility of observing many scales of turbulence and tracer variability. This study uses Argo salinity data to form the second-order tracer structure function at the macro-scale (10−1000 km, mesoscale and above). When turbulence is homogeneous, the structure function slope from Argo can be related to the wavenumber spectrum slope in ocean’s salinity variability. In the oceans, where turbulence is mostly heterogeneous, spectra may be misleading, but structure functions still provide statistical information that can be used for model validation. With growing interest in extracting renewable forms of energy, marine hydrokinetic energy from waves, tides, and ocean currents is increasing in favor. Tidal energy conversation is of particular interest in the Puget Sound, WA where narrow channels and large tidal ranges have the ability to produce more than 0.6 terawatt-hours per year of extractable power, but a better understanding of the marine environment is needed to make further progress in research and development of these new technologies. Turbulence, in particular, is both extremely impactful and difficult to observe and predict. Observations are crucial for this task, but limited observing capabilities require additional information from numerical models. First, acoustic Doppler velocimeter observations are used to perform a detailed characterization of the turbulent flow at Nodule Point in the Puget Sound, including quantifications of anisotropy and coherence. Beyond the limited single-point observations, two foundationally different numerical models are analyzed for their ability to create realistic tidal turbulence. A stochastic turbulence generator and large-eddy simulation model are compared to the observations from Nodule Point, focusing on anisotropy and coherence to more-fully characterize the turbulent features of the tidal strait. With a similar interest in improving forecasts of renewable energy resources, atmospheric turbulence is observed at the Boulder Atmospheric Observatory in the Summer of 2014 prior to an upcoming Wind Forecast Improvement Project field campaign. Dissipation rates will be calculated from wind profiling radars to determine the optimal measurement techniques to be used next Fall for WFIP2. Tunable parameters and radar configurations are discussed, with the method for calculating "true" dissipation rates from sonic anemometer measurements.