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Melissa Moulton

Research Scientist/Engineer Senior

Email

mmoulton@apl.washington.edu

Phone

206-221-7623

Research Interests

Coastal and Nearshore Processes, Environmental Fluid Mechanics, Remote Sensing, Beach Hazard Prediction

Biosketch

Dr. Moulton's recent research includes studying strong, offshore-directed jets known as rip currents which can carry pollutants, larvae, and heat from the shoreline to the inner shelf and are hazardous to swimmers. Her work seeks to improve understanding and prediction of rip currents using field observations and numerical simulations. (http://www.whoi.edu/oceanus/feature/the-riddle-of-rip-currents) In addition, Dr. Moulton is investigating inner shelf processes using airborne remote sensing, drifters, and numerical models.

Education

B.A. Physics, Amherst College, 2009

Ph.D. Physical Oceanography, MIT/WHOI Joint Program, 2016

Publications

2000-present and while at APL-UW

Comparison of rip current hazard likelihood forecasts with observed rip current speeds

Moulton, M., G. Dusek, S. Elgar, and B. Raubenheimer, "Comparison of rip current hazard likelihood forecasts with observed rip current speeds," Wea. Forecasting, 32, 1659-1666, doi:10.1175/WAF-D-17-0076.1, 2017.

More Info

1 Aug 2017

Although rip currents are a major hazard for beachgoers, the relationship between the danger to swimmers and the physical properties of rip current circulation is not well understood. Here, the relationship between statistical model estimates of hazardous rip current likelihood and in situ velocity observations is assessed. The statistical model is part of a forecasting system that is being made operational by the National Weather Service to predict rip current hazard likelihood as a function of wave conditions and water level. The temporal variability of rip current speeds (offshore-directed currents) observed on an energetic sandy beach is correlated with the hindcasted hazard likelihood for a wide range of conditions. High likelihoods and rip current speeds occurred for low water levels, nearly shore-normal wave angles, and moderate or larger wave heights. The relationship between modeled hazard likelihood and the frequency with which rip current speeds exceeded a threshold was assessed for a range of threshold speeds. The frequency of occurrence of high (threshold exceeding) rip current speeds is consistent with the modeled probability of hazard, with a maximum Brier skill score of 0.65 for a threshold speed of 0.23 m s-1, and skill scores greater than 0.60 for threshold speeds between 0.15 and 0.30 m s-1. The results suggest that rip current speed may be an effective proxy for hazard level and that speeds greater than ~0.2 m s-1 may be hazardous to swimmers.

Rip currents and alongshore flows in single channels dredged in the surf zone

Moulten, M., S. Elgar, B. Raubenheimer, J.C. Warner, and N. Kumar, "Rip currents and alongshore flows in single channels dredged in the surf zone," J. Geophys. Res. Oceans, 122, doi:10.1002/2016JC012222, 2017.

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8 May 2017

To investigate the dynamics of flows near nonuniform bathymetry, single channels (on average 30 m wide and 1.5 m deep) were dredged across the surf zone at five different times, and the subsequent evolution of currents and morphology was observed for a range of wave and tidal conditions. In addition, circulation was simulated with the numerical modeling system COAWST, initialized with the observed incident waves and channel bathymetry, and with an extended set of wave conditions and channel geometries. The simulated flows are consistent with alongshore flows and rip-current circulation patterns observed in the surf zone. Near the offshore-directed flows that develop in the channel, the dominant terms in modeled momentum balances are wave-breaking accelerations, pressure gradients, advection, and the vortex force. The balances vary spatially, and are sensitive to wave conditions and the channel geometry. The observed and modeled maximum offshore-directed flow speeds are correlated with a parameter based on the alongshore gradient in breaking-wave-driven-setup across the nonuniform bathymetry (a function of wave height and angle, water depths in the channel and on the sandbar, and a breaking threshold) and the breaking-wave-driven alongshore flow speed. The offshore-directed flow speed increases with dissipation on the bar and reaches a maximum (when the surf zone is saturated) set by the vertical scale of the bathymetric variability.

Inner Shelf Dynamics Science and Experiment Plan

Feddersen, F., et al., "Inner Shelf Dynamics Science and Experiment Plan," APL-UW TR 1602, Technical Report, Applied Physics Laboratory, University of Washington, Seattle, October 2016, 35pp.

More Info

31 Oct 2016

The deep ocean, continental shelf, and surf zone are defined by their unique physical processes and dynamics. The nearshore region from about 50 m water depth to the outer edge of the surf zone (SZ) is known as the inner shelf. This region is characterized by overlapping and interacting surface and bottom boundary layers. At the offshore side of the inner shelf, instabilities from wind-driven currents and fronts create cross-shelf meanders and eddies. In addition, energetic nonlinear internal waves (NLIWs) are ubiquitous on the inner shelf.

To understand and predict the exchange of water properties (heat, gases, sediment, pollutants, biota) across the inner shelf over a range of temporal and spatial scales, the Office of Naval Research Inner Shelf Dynamics Departmental Research Initiative (Inner Shelf DRI) is coordinating field observations (in situ and remote sensing) coupled to numerical modeling efforts on a 50-km section of coast off Vandenberg Air Force Base, California, located in the vicinity of Point Sal. The overall goal is to develop and improve the predictive capability of a range of numerical models to simulate the 3D circulation, density, and surface wave field across the inner shelf associated with a broad array of physical processes and complex bathymetry.

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
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