5,158 research outputs found
Stability of a coastal upwelling front over topography
Get PDFSubmitted in partial fulfillment of the requirements for the degree of Doctor of Philosophy at the Massachusetts Institute of Technology and the Woods Hole Oceanographic Institution October 1987A two-layer shallow water equation model is used to investigate the linear
stability of a coastal upwelling front. The model features a surface front near a
coastal boundary and bottom topography which is an arbitrary function of the
cross-shelf coordinate. By combining the various conservation statements for the
global properties of the system, a general stability theorem is established which
allows the a priori determination of the stability of a coastal upwelling front.
Unstable waves are found for the modelled coastal upwelling front. The unstable
wave motions are frontally-trapped and dominant in the upper layer. The wave
propagates phase in the direction of the basic state flow and the primary energy
conversion is via baroclinic instability. The effect of varying the model parameters
is presented. Moving the front closer than ~ 2 Rossby radii to the coastal boundary
results in a decrease in the growth rate of the fastest growing wave. Increasing
the overall vertical shear of the basic state flow, by either decreasing the lower
layer depth or increasing the steepness of the interface, results in an increase in
the growth of the fastest growing wave.
A bottom sloping in the same sense as the interface results in a decrease of
the growth rates and alongfront wavenumbers of the unstable waves in the system.
Linearized bottom friction is included in the stability model and results in a
decrease in the growth rates of the unstable waves by extracting energy from the
system. Since the unstable mode is strongest in the upper layer, bottom friction
will not stabilize the upwelling front.
A comparison between the predictions from the simple two-layer model and
observed alongfront variability for three areas of active upwelling is presented.
Reasonable agreement is found, suggesting that observed alongfront variability
can be interpreted in terms of the instability of a coastal upwelling front.This study was supported by the National Science Foundation Grant
OCE 84-08563 and the Office of Naval Research Coastal Ocean Sciences
Program 10/1984.37
Rambling Mose : Characteristic March & Two Step
Get PDFhttps://digitalcommons.library.umaine.edu/mmb-ps/1344/thumbnail.jp
Arsenic detection project: electronics
Get PDFThis project is a collaboration with a team of bioengineers to adapt the functionality of laboratory equipment onto a platform which could be used in the field to determine the concentration levels of toxins in ground water. To this end, using a set of printed electrodes, a device was designed and fabricated with the constraints of field use in mind: low power, low cost, with a mobile user interface. An Android phone served as the mobile user interface, and also as the power supply for the circuit and microcontroller that performed the test. This circuit applied a stimulus voltage across the electrodes and generated an output signal using annodic stripping voltammetry. The microcontroller both generated that stimulus signal, and interpreted the output signal for transmission to the mobile phone where the user then interpreted the data. Testing showed that, in addition to running the expected test for arsenic, the device was able to communicate those results to the mobile phone. Subsequent visual inspection of these results confirmed that control and contaminated samples could be correctly identified from the phone
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