Researchers
Chris Chickadel
Chair, AIRS Department
Senior Principal Oceanographer
AIRS Department
APL-UW
Affiliate Associate Professor, Civil and Environmental Engineering
Andy Jessup
Senior Principal Oceanographer
AIRS Department
APL-UW
Professor, Civil and Environmental Engineering and Affiliate Associate Professor, Mechanical Engineering
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Sensitive video, microwave radar, and infrared sensors capture small differences in surface water temperature and surface ripple patterns — important clues to what is happening below, out of sight.
Anybody who wants to navigate a river would like to know where there are hazards to navigation, simply whether it’s deep or shallow so you can get a vessel in. It’s important for the Navy if they need to go into an area where they don’t have measurements. For operations they need to know how fast the river is flowing, how deep it is… So we are investigating the utility of remote sensing techniques to help inform them.
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More About This Research
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COHSTREX Website
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Remote Sensing of Coherent Structure Reveals Riverine Flow (PDF, 419 KB)
By Trina Litchendorf. Feature article from the APL-UW Biennial Report, 2007. |
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Publications
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Frontogenesis and frontal progression of a trapping-generated estuarine convergence front and its influence on mixing and stratification Giddings, S.N., D.A. Fong, S.G. Monismith, C.C. Chickadel, K.A. Edwards, W.J. Plant, B. Wang, O.B. Fringer, A.R. Horner-Devine, and A.T. Jessup, "Frontogenesis and frontal progression of a trapping-generated estuarine convergence front and its influence on mixing and stratification," Estuar. Coasts, 35, 665-681, doi:10.1007/s12237-011-9453-z, 2012. |
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1 Mar 2012
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Estuarine fronts are well known to influence transport of waterborne constituents such as phytoplankton and sediment, yet due to their ephemeral nature, capturing the physical driving mechanisms and their influence on stratification and mixing is difficult. We investigate a repetitive estuarine frontal feature in the Snohomish River Estuary that results from complex bathymetric shoal/channel interactions. In particular, we highlight a trapping mechanism by which mid-density water trapped over intertidal mudflats converges with dense water in the main channel forming a sharp front. The frontal density interface is maintained via convergent transverse circulation driven by the competition of lateral baroclinic and centrifugal forcing. The frontal presence and propagation give rise to spatial and temporal variations in stratification and vertical mixing. Importantly, this front leads to enhanced stratification and suppressed vertical mixing at the end of the large flood tide, in contrast to what is found in many estuarine systems. The observed mechanism fits within the broader context of frontogenesis mechanisms in which varying bathymetry drives lateral convergence and baroclinic forcing. We expect similar trapping-generated fronts may occur in a wide variety of estuaries with shoal/channel morphology and/or braided channels and will similarly influence stratification, mixing, and transport.
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Infrared-based measurements of velocity, turbulent kinetic energy, and dissipation at the water surface in a tidal river Chickadel, C.C., S.A. Talke, A.R Horner-Devine, and A.T. Jessup, "Infrared-based measurements of velocity, turbulent kinetic energy, and dissipation at the water surface in a tidal river," IEEE Geosci. Remote Sens. Lett., 8, 849-853, doi:10.1109/LGRS.2011.2125942, 2011. |
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1 Sep 2011
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Thermal infrared (IR)-based particle image velocimetry (PIV) is used to measure the evolution of velocity, turbulent kinetic energy (TKE), and the TKE dissipation rate at the water surface in the tidally influenced Snohomish River. Patterns of temperature variability in the IR imagery arise from disruption of the cool-skin layer and are used to estimate the 2-D velocity field. Comparisons of IR-based PIV mean velocity made with a colocated acoustic velocimeter demonstrate high correlation. IR-based PIV provides detailed measurements of previously inaccessible surface velocities and turbulence statistics.
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Remotely sensed river surface features compared with modeling and in situ measurements Plant, W.J., R. Branch, G. Chatham, C.C. Chickadel, K. Hayes, B. Hayworth, A. Horner-Devine, A. Jessup, D.A. Fong, O.B. Fringer, S.N. Giddings, S. Monismith, and B. Wang, "Remotely sensed river surface features compared with modeling and in situ measurements," J. Geophys. Res., 114, doi:10.1029/2009JC005440, 2009. |
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3 Nov 2009
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Images of river surface features that reflect the bathymetry and flow in the river have been obtained using remote sensing at microwave, visible, and infrared frequencies. The experiments were conducted at Jetty Island near the mouth of the Snohomish River at Everett, Washington, where complex tidal flow occurs over a varied bathymetry, which was measured as part of these experiments. An X band (9.36 GHz) Doppler radar was operated from the river bank and produced images of normalized radar cross sections and radial surface velocities every 20 min over many tidal cycles. The visible and infrared instruments were flown in an airplane. All of these techniques showed surface evidence of frontal features, flow over a sill, and flow conditioned by a deep hole. These features were modeled numerically, and the model results correspond well to the remote observations. In situ measurements made near the hole showed that changes in measured velocities correlate well with the occurrence of the features in the images. In addition to tidal phase, the occurrence of these features in the imagery depends on tidal range. The surface roughness observed in the imagery appears to be generated by the bathymetry and flow themselves rather than by the modulation of wind waves.
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Vertical boil propagation from a submerged estuarine sill Chickadel, C.C., A.R. Horner-Devine, S.A. Talke, and A.T. Jessup, "Vertical boil propagation from a submerged estuarine sill," Geophys. Res. Lett., 36, doi:10.1029/2009GL037278, 2009. |
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20 May 2009
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Surface disruptions by boils during strong tidal flows over a rocky sill were observed in thermal infrared imagery collected at the Snohomish River estuary in Washington State. Locations of boil disruptions and boil diameters at the surface were quantified and are used to test an idealized model of vertical boil propagation. The model is developed as a two-dimensional approximation of a three-dimensional vortex loop, and boil vorticity is derived from the flow shear over the sill. Predictions of boil disruption locations were determined from the modeled vertical velocity, the sill depth, and the over-sill velocity. Predictions by the vertical velocity model agree well with measured locations (rms difference 3.0 m) and improve by using measured velocity and shear (rms difference 1.8 m). In comparison, a boil-surfacing model derived from laboratory turbulent mixed-layer wakes agrees with the measurements only when stratification is insignificant.
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