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D
Suanda, SH, Barth JA, Woodson CB.  2011.  Diurnal heat balance for the northern Monterey Bay inner shelf. Journal of Geophysical Research: Oceans. 116:C09030.   10.1029/2010JC006894   AbstractWebsite

In the summer of 2007, physical measurements including velocity from acoustic Doppler current profilers, surface gravity wave heights measured acoustically, and temperature from thermistor chain arrays were collected along- and across- the mid to inner shelf (water depths from 10ā€“60 m) in northern Monterey Bay. The oceanic response to a strong (8ā€“15 m sāˆ’1 daily maximum) along-shelf sea breeze is examined by evaluating the diurnal heat budget over a cross-shelf section of the inner shelf. The diurnal heat budget closes to within the 95% confidence level with daily warming and cooling periods explained by two separate, but related processes. During evening/early morning warming period, 77% of the observed temperature increase is due to along-shelf advection of a temperature gradient within the upwelling shadow zone, a process which is arrested during the period of wind-forcing. In contrast, 75% of the afternoon cooling period is explained by the cross-shelf heat flux driven by diurnal along-shelf winds. In this study, diurnal tides are found to contribute less than 10% of the observed temperature variability and surface gravity waves do not show any significant diurnal variability. Richardson number estimates show that, on average, wind-induced shear is not strong enough to erode the strength of water column stratification within the upwelling shadow.

E
Suanda, SH, Feddersen F, Kumar N.  2017.  The effect of barotropic and baroclinic tides on coastal stratification and mixing. Journal of Geophysical Research-Oceans. 122:10156-10173.   10.1002/2017jc013379   AbstractWebsite

The effects of barotropic and baroclinic tides on subtidal stratification and vertical mixing are examined with high-resolution, three-dimensional numerical simulations of the Central Californian coastal upwelling region. A base simulation with realistic atmospheric and regional-scale boundary forcing but no tides (NT) is compared to two simulations with the addition of predominantly barotropic local tides ( LT) and with combined barotropic and remotely generated, baroclinic tides (WT) with approximate to 100 W m(-1) onshore baroclinic energy flux. During a 10 day period of coastal upwelling when the domain volume-averaged temperature is similar in all three simulations, LT has little difference in subtidal temperature and stratification compared to NT. In contrast, the addition of remote baroclinic tides (WT) reduces the subtidal continental shelf stratification up to 50% relative to NT. Idealized simulations to isolate barotropic and baroclinic effects demonstrate that within a parameter space of typical U.S. West Coast continental shelf slopes, barotropic tidal currents, incident energy flux, and subtidal stratification, the dissipating baroclinic tide destroys stratification an order of magnitude faster than barotropic tides. In WT, the modeled vertical temperature diffusivity at the top (base) of the bottom (surface) boundary layer is increased up to 20 times relative to NT. Therefore, the width of the inner-shelf ( region of surface and bottom boundary layer overlap) is increased approximately 4 times relative to NT. The change in stratification due to dissipating baroclinic tides is comparable to the magnitude of the observed seasonal cycle of stratification.

Suanda, SH, Perez S, Feddersen F.  2016.  Evaluation of a source-function wavemaker for generating random directionally spread waves in the sea-swell band. Coastal Engineering. 114:220-232.   10.1016/j.coastaleng.2016.04.006   AbstractWebsite

A source-function wavemaker for wave-resolving models is evaluated for its capability to reproduce random directionally spread wave fields in the sea-swell band (0.04-0.3 Hz) relevant for realistic nearshore applications. The wavemaker is tested with a range of input wave characteristics defined by the non-dimensional amplitude (a/h), wavenumber (kh), wavemaker width, mean wave angle and directional spread. The (a/h) and kh dependency of modeled results are collapsed with the Ursell number (Ur= (a/h)/(kh)(2)). For monochromatic waves, the wavemaker accurately reproduced the input wave height for Ur<1, with no dependence on non dimensional wavemaker width. For random uni-directional waves, the wavemaker simulated well a Pierson Moskowitz input spectrum. Frequency-integrated statistics are also reproduced with less than 2% difference between modeled to input significant wave height and <10% difference between modeled to input mean frequency for Ur<0.2. For random directionally spread waves, the wavemaker reproduced input frequency dependent and bulk mean wave angle and directional spread to within 4 degrees at Ur<0.12. Lastly, the wavemaker simulated well the spectra, mean wave angle, and directional spread of a bimodal wave field with opposing sea and swell. Based on the Ur<0.12 constraint, a range of dimensional wave height, period, and depth constraints are explored for realistic sea-swell band field application. The wavemaker's ability to generate waves that match the input statistical properties commonly derived from field measurements demonstrates that it can be used effectively in a range of nearshore science and engineering applications. (C) 2016 Elsevier B.V. All rights reserved.

M
Kumar, N, Feddersen F, Suanda S, Uchiyama Y, McWilliams J.  2016.  Mid- to inner-shelf coupled ROMS-SWAN model-data comparison of currents and temperature: Diurnal and semidiurnal variability. Journal of Physical Oceanography. 46:841-862.   10.1175/jpo-d-15-0103.1   AbstractWebsite

Accurately representing diurnal and semidiurnal internal variability is necessary to investigate inner-shelf to midshelf exchange processes. Here, a coupled Regional Ocean Model System (ROMS)-Simulating Waves Nearshore (SWAN) model is compared to observed diurnal and semidiurnal internal tidal variability on the mid and inner shelf (26-8 m water depth) near San Pedro Bay, California. Modeled mean stratification is about one-half of that observed. Modeled and observed baroclinic velocity rotary spectra are similar in the diurnal and semidiurnal band. Modeled and observed temperature spectra have similar diurnal and semidiurnal band structure, although the modeled is weaker. The observed and modeled diurnal and semidiurnal baroclinic velocity- and temperature-dominant vertical structures are similar and consistent with mode-one internal motions. Both observed and modeled diurnal baroclinic kinetic energy are strongly correlated to diurnal wind forcing and enhanced by subtidal vorticity-induced reduction in the inertial frequency. The mid- and inner-shelf modeled diurnal depth-integrated heat budget is a balance between advective heat flux divergence and temperature time derivative. Temperature-velocity phase indicates progressive semidiurnal internal tide on the midshelf and largely standing internal tide on the inner shelf in both observed and modeled. The ratio of observed to modeled inferred phase speed is consistent with the observed to modeled stratification. The San Pedro Bay modeled semidiurnal internal tide has significant spatial variability, variable incident wave angles, and multiple local generation sites. Overall, the coupled ROMS-SWAN model represents well the complex diurnal and semidiurnal internal variability from the mid to the inner shelf.

Tlusty, MF, Metzler A, Huckabone S, Suanda S, Guerrier S.  2009.  Morphological colour change in the American lobster (Homarus americanus) in response to background colour and UV light. New Zealand Journal of Marine and Freshwater Research. 43:247-255.: Taylor & Francis   10.1080/00288330909509998   AbstractWebsite

Abstract American lobster (Homarus americanus) have a thick calcified cuticle, and do not exhibit rapid colour changes characteristic of other crustaceans. Thus, the plasticity of their coloration has been largely overlooked. Colour in lobsters is determined by the amount, location, and form of the carotenoid pigment astaxanthin, and it is possible for lobsters to alter colour by changing one of these characteristics of astaxanthin deposition. Here, short?term colour variation in American lobster in response to environmental cues (background colour and ultraviolet (UV) light) was investigated in a laboratory experiment. Lobsters were reared in conditions controlling background colour (white, black) and UV light (present, absent). Digital photographic analysis was used to determine how these conditions influenced the luminescence (light or dark) of lobster colour, as well as the ratio of red to blue hues. Of the environmental variables considered within this experiment, UV light was the predominant factor, and caused lobsters to become darker in colour. In the absence of UV light, lobsters matched background colour, and turned darker in response to the darker background. Environmental matching has practical implications both for wild lobsters as they settle to the benthic habitat, and for enhancement programmes, to grow lobsters that are best suited for local habitats.American lobster (Homarus americanus) have a thick calcified cuticle, and do not exhibit rapid colour changes characteristic of other crustaceans. Thus, the plasticity of their coloration has been largely overlooked. Colour in lobsters is determined by the amount, location, and form of the carotenoid pigment astaxanthin, and it is possible for lobsters to alter colour by changing one of these characteristics of astaxanthin deposition. Here, short?term colour variation in American lobster in response to environmental cues (background colour and ultraviolet (UV) light) was investigated in a laboratory experiment. Lobsters were reared in conditions controlling background colour (white, black) and UV light (present, absent). Digital photographic analysis was used to determine how these conditions influenced the luminescence (light or dark) of lobster colour, as well as the ratio of red to blue hues. Of the environmental variables considered within this experiment, UV light was the predominant factor, and caused lobsters to become darker in colour. In the absence of UV light, lobsters matched background colour, and turned darker in response to the darker background. Environmental matching has practical implications both for wild lobsters as they settle to the benthic habitat, and for enhancement programmes, to grow lobsters that are best suited for local habitats.

S
Suanda, SH, Feddersen F.  2015.  A self-similar scaling for cross-shelf exchange driven by transient rip currents. Geophysical Research Letters. 42:5427-5434.   10.1002/2015GL063944   Abstract

Transient rip currents, episodic offshore flows from the surf zone to the inner shelf, present a recreational beach hazard and exchange material across the nearshore ocean. The magnitude and offshore extent of transient rip-current-induced exchange and its relative importance to other inner shelf exchange processes are poorly understood. Here 120 model simulations with random, normally incident, directionally spread waves spanning a range of beach slopes and wave conditions show that the transient rip current exchange velocity is self-similar. The nondimensional exchange velocity, surf zone flushing time, and cross-shore decay length scale are scaled by beach slope and wave properties, depending strongly on wave directional spread. Transient rip-current-driven exchange can be compared to other cross-shelf exchange processes. For example, transient rip-current-driven exchange is stronger than wave-induced Stokes-drift-driven exchange up to six surf zone widths from shore.

Suanda, SH, Barth JA.  2015.  Semidiurnal baroclinic tides on the central Oregon inner shelf. Journal of Physical Oceanography. : American Meteorological Society   10.1175/JPO-D-14-0198.1   Abstract

AbstractSemidiurnal velocity and density oscillations are examined over the mid and inner continental shelf near Heceta Bank on the Oregon coast. Measurements from two long-term observation networks with sites on and off the submarine bank reveal that both baroclinic velocities and displacements are dominated by the first mode, with larger velocities on the mid shelf and northern parts of the bank. Mid-shelf sites have current ellipses that are near the theoretical value for single, progressive internal tidal waves compared to more linearly polarized currents over the inner shelf. Baroclinic current variability is not correlated to the spring-neap cycle and is uncorrelated between mooring locations. An idealized model of two internal waves propagating from different directions reproduces some of the observed variability in semidiurnal ellipse parameters. At times, the phasing between moorings along a cross-shelf transect are consistent with onshelf wave propagation, a characteristic also present in the output of a three-dimensional regional circulation model. Regional wind-driven upwelling/downwelling influences stratification at all shelf moorings. At locations north of the bank, stronger baroclinic velocities were found during periods of higher background stratification.

Suanda, SH, Barth JA, Holman RA, Stanley J.  2014.  Shore-based video observations of nonlinear internal waves across the inner shelf. Journal of Atmospheric and Oceanic Technology. 31:714-728.: American Meteorological Society   10.1175/JTECH-D-13-00098.1   AbstractWebsite

AbstractShore-based video remote sensing is used to observe and continually monitor nonlinear internal waves propagating across the inner shelf. Month-long measurements of velocity from bottom-mounted acoustic Doppler current profilers and temperature from thermistor chains at the 10- and 20-m isobaths are combined with sea surface imagery from a suite of cameras (Argus) to provide a kinematic description of 11 borelike internal waves as they propagate across the central Oregon inner shelf. The surface expression of these waves, commonly seen by eye as alternating rough and smooth bands, are identified by increased pixel intensity in Argus imagery (average width 39 Ā± 6 m), caused by the convergence of internal wave-driven surface currents. These features are tracked through time and space using 2-min time exposure images and then compared to wave propagation speed and direction from in situ measurements. Internal waves are refracted by bathymetry, and the measured wave speed (~0.15 m s?1) is higher than predicted by linear theory (<0.1 m s?1). Propagating internal waves are also visible in subsampled Argus pixel time series (hourly collections of 17 min worth of 2-Hz pixel intensity from a subset of locations), thus extending the observational record to times without an in situ presence. Results from this 5-month record show that the preferred sea state for successful video observations occurs for wind speeds of 2?5 m s?1. Continued video measurements and analysis of extensive existing Argus data will allow a statistical estimate of internal wave occurrence at a variety of inner-shelf locations.

W
Suanda, SH, Kumar N, Miller AJ, Di Lorenzo E, Haas K, Cai DH, Edwards CA, Washburn L, Fewings MR, Torres R, Feddersen F.  2016.  Wind relaxation and a coastal buoyant plume north of Pt. Conception, CA: Observations, simulations, and scalings. Journal of Geophysical Research-Oceans. 121:7455-7475.   10.1002/2016jc011919   AbstractWebsite

In upwelling regions, wind relaxations lead to poleward propagating warm water plumes that are important to coastal ecosystems. The coastal ocean response to wind relaxation around Pt. Conception, CA is simulated with a Regional Ocean Model (ROMS) forced by realistic surface and lateral boundary conditions including tidal processes. The model reproduces well the statistics of observed subtidal water column temperature and velocity at both outer and inner-shelf mooring locations throughout the study. A poleward-propagating plume of Southern California Bight water that increases shelf water temperatures by similar to 5 degrees C is also reproduced. Modeled plume propagation speed, spatial scales, and flow structure are consistent with a theoretical scaling for coastal buoyant plumes with both surface-trapped and slope-controlled dynamics. Plume momentum balances are distinct between the offshore (>30 m depth) region where the plume is surface-trapped, and onshore of the 30 m isobath (within 5 km from shore) where the plume water mass extends to the bottom and is slope controlled. In the onshore region, bottom stress is important in the alongshore momentum equation and generates vertical vorticity that is an order of magnitude larger than the vorticity in the plume core. Numerical experiments without tidal forcing show that modeled surface temperatures are biased 0.5 degrees C high, potentially affecting plume propagation distance and persistence.