APL-UW Home

Jobs
About
Campus Map
Contact
Privacy
Intranet

Kristin Zeiden

Research Scientist/Engineer - Senior

Email

kzeiden@uw.edu

Phone

206-543-9891

Education

B.S. Astrophysics, University of California, Los Angeles, 2011

Ph.D. Oceanography, University of California, San Diego, 2021

Publications

2000-present and while at APL-UW

Observations of elevated mixing and periodic structures within diurnal warm layers

Zeiden, K., J. Thomson, A. Shcherbina, and E. D'Asaro, "Observations of elevated mixing and periodic structures within diurnal warm layers," J. Geophys. Res., 129, doi:10.1029/2024JC021399, 2024.

More Info

9 Nov 2024

Surface drifters (SWIFTs) equipped with down-looking high-resolution acoustic doppler current profilers (ADCPs) were used to estimate the turbulent kinetic energy (TKE) dissipation rate (ε) within highly stratified diurnal warm layers (DWLs) in the Southern California Bight. Over a 10-day period, five instances of DWLs were observed with strong surface temperature anomalies up to 3°C and velocity anomalies up to 0.3 m s-1. Profiles of ε in the upper 5 m suggest turbulence is strongly modulated by the DWL stratification. Burst-averaged (8.5 min) ε is stronger than predicted by law-of-the-wall boundary layer scaling within the DWLs and suppressed below. Predictions for ε within the DWLs are improved by a shear-production scaling using observed shear and linearly decaying turbulent stress. However, ε is still under-predicted. Examination of the un-averaged acoustic backscatter data suggests elevated ε is related to the presence of turbulent structures in the DWLs which span the layer height and strongly modulate TKE. Evolution in the bulk Richardson number each day suggests the DWLs become unstable to layer-scale overturning and entrainment each afternoon, thus the turbulent structures may result from shear-driven instability. This interpretation is supported by a conditional average of the data during a burst characterized by strongly periodic structures. The structures resemble high-frequency internal waves with strong asymmetry in the along-flow direction (steepening) which suggests they are unstable. Coincident asymmetric patterns in upwelling/downwelling and corresponding regions of strong vertical convergence/divergence suggest that both vertical transport and local TKE generation are plausible sources of elevated ε in the DWLs.

Observations of elevated mixing and periodic structures within diurnal warm layers

Zeiden, K., J. Thomson, A. Shcherbina, and E. D'Asaro, "Observations of elevated mixing and periodic structures within diurnal warm layers," J. Geophys. Res., 129, doi:10.1029/2024JC021399, 2024.

More Info

9 Nov 2024

Surface drifters (SWIFTs) equipped with down-looking high-resolution acoustic doppler current profilers (ADCPs) were used to estimate the turbulent kinetic energy (TKE) dissipation rate
(ε) within highly stratified diurnal warm layers (DWLs) in the Southern California Bight. Over a 10-day period, five instances of DWLs were observed with strong surface temperature anomalies up to 3°C and velocity anomalies up to 0.3 m s-1. Profiles of
ε in the upper 5 m suggest turbulence is strongly modulated by the DWL stratification. Burst-averaged (8.5 min) ε is stronger than predicted by law-of-the-wall boundary layer scaling within the DWLs and suppressed below. Predictions for ε within the DWLs are improved by a shear-production scaling using observed shear and linearly decaying turbulent stress. However, ε is still under-predicted. Examination of the un-averaged acoustic backscatter data suggests elevated ε is related to the presence of turbulent structures in the DWLs which span the layer height and strongly modulate TKE. Evolution in the bulk Richardson number each day suggests the DWLs become unstable to layer-scale overturning and entrainment each afternoon, thus the turbulent structures may result from shear-driven instability. This interpretation is supported by a conditional average of the data during a burst characterized by strongly periodic structures. The structures resemble high-frequency internal waves with strong asymmetry in the along-flow direction (steepening) which suggests they are unstable. Coincident asymmetric patterns in upwelling/downwelling and corresponding regions of strong vertical convergence/divergence suggest that both vertical transport and local TKE generation are plausible sources of elevated ε in the DWLs.

Measuring turbulence from wave-following platforms

Zeiden, K., and J. Thomson, "Measuring turbulence from wave-following platforms," In Proc., IEEE/OES 13th Current, Waves and Turbulence Measurement (CWTM), 18-20 March 2024, Wanchese, NC, doi:10.1109/CWTM61020.2024.10526345 (IEEE, 2024).

More Info

15 May 2024

Autonomous surface platforms equipped with pulse-coherent high-resolution (HR) ADCPs are a promising tool for measuring turbulence and estimating turbulent dissipation rates, ε(z), close to the air-sea interface. However, surface gravity waves generate significant bias in ε(z) if not sufficiently separated from the turbulent signal. In a previous study, the authors developed a method of isolating wave orbital velocities from the data using empirical orthogonal functions (EOFs). Low-mode EOFs had characteristics of surface gravity waves, while higher-mode EOFs had characteristics of turbulence. After filtering empirical wave profiles constructed from the low-mode EOFs from the data, resultant ε(z) were in close agreement with law-of-the-wall scaling during quiescent conditions. In this study, we further validate the EOF-filtering technique by comparing EOFs of the HR ADCP data with those computed from synthetic wave data which does not contain turbulence. As expected, low-mode EOFs of the synthetic data are in strong agreement with those of the real data, while high-mode EOFs reflect only noise due to the absence of turbulence. Wave profiles constructed from the low-mode EOFs are then used to quantify the potential for bias in ε(z) if wave velocities are not sufficiently filtered from the data.

More Publications

Acoustics Air-Sea Interaction & Remote Sensing Center for Environmental & Information Systems Center for Industrial & Medical Ultrasound Electronic & Photonic Systems Ocean Engineering Ocean Physics Polar Science Center
Close

 

Close