Near-inertial summary about internal_waves_barkley_canyon HOT 3 CLOSED

Generated f depth-band plots, getting started on interpretation (there is more than this, based on the comparative PSD and rotary spectra plots).

Wind plots very necessary for near-inertial investigation (work-in-progress):

Upper Slope

• Inertial power distributed fairly equally between cross- and along-slope spectra.
• Nearly entirely in the CW component, as expected in the northern hemisphere.
• Distributed equally through depth, though there may be some reduction approaching the bottom.
• Peaks seem correlated with regional wind events, with direction being important in how much effect occurs. It's interesting that some of earlier events don't seem to appear, at all.

Axis

• There is rectilinear flow in the along-canyon direction, with equal distribution between CW and CCW components.
• Through depth, there is similar bottom amplification as seen in the K1 signal.
• Peaks appear similarly correlated to weather events, as at Upper Slope.

from internal_waves_barkley_canyon.

• Notable effects: No apparent blue-shift. CW weakening near shelf, CCW intensification. Seasonality (wind). Canyon-axis intensification, even though the signal appears to weaken with depth.

Inertial outline

Upper Slope - Near-shelf deintensification

Describe (what do I see):

• Depth-averaged / multi-annual time-averaged PSD comparison to K1 and M2 (K1 < f < M2, shape of peak, etc.).
• No apparent blue-shift in spectral peak (this is interesting).
• Equally distributed between cross- and along-slope, and nearly entirely CW, as expected for Coriolis affected motions in the northern hemisphere.
• Below about -250 m there is a weakening of the cross- and along-slope, CW inertial signal by about an order of magnitude.
• Vertical scale of effect approximately 150 m AB.
• Some intensification of the CCW signal near the bottom (about an order of magnitude, about 150 m AB).
• Seasonality seems intrinsically linked to major wind events, and can occur at any point each year when a storm passes (seems somewhat more likely during the fall/winter (compare wind data), but doesn't always happen (this is interesting). This is most evident in the upper depths AND the bottom-intensified layer, separately for CW and CCW, respectively.
• There is little to no evidence of spring-neap modulation, in contrast to what is seen in K1.
• Be sure these are all quantified and related in clear figures.

Compare (what did others see):

• Poulain et al., 1992.
• Kampf, 2018.
• Thomson et al., 1990. Noted near-inertial attenuation in a lower critical layer about 200 m thick.
• Alford et al., 2012.
• Chapman, 1983.
• Gilmour, 1987.
• Xu & Noble, 2009.
• Cuypers et al., 2017.
• Mihaly et al., 1998.
• Quantify (compare) where possible.
• Find additional sources.

Explain (what may be causing this):

• Thomson et al., 1990. Critical layer attenuation of downward near-inertial motions as they are absorbed by increased vertical shear in the background flow due to bottom-trapped oscillations over ridge topography.
• Discuss strengths and weaknesses of each theory.

Axis - Canyon-axis intensification

Describe (what do I see):

• Depth-averaged / multi-annual time-averaged PSD comparison to f and M2 (f < K1 < M2, shape of peak, etc.).
• No apparent blue-shift in spectral peak (this is interesting).
• Mostly along-canyon, rectilinear, as expected for canyon-guided flow.
• Below -750 m intensification in along-canyon, CW and CCW signals, of about 2x orders of magnitude (as seen in K1, M2, etc.).
• Vertical scale of effect approximately 250 m AB.
• Seasonality related to notable wind events, mostly fall/winter (similar to Upper Slope; weather data), most evident in the bottom-intensified layer below -750 m.
• There may be weak spring-neap modulation (compare depth-mean to surface tides).
• Be sure these are all quantified and related in clear figures.

Compare (what did others see):

• Poulain et al., 1992.
• Kampf, 2018.
• Thomson et al., 1990.
• Alford et al., 2012.
• Chapman, 1983.
• Gilmour, 1987.
• Xu & Noble, 2009.
• Cuypers et al., 2017.
• Mihaly et al., 1998.
• Quantify (compare) where possible.
• Find additional sources.

Explain (what may be causing this):

• Discuss strengths and weaknesses of each theory.

To associate wind-field events with the observed signals:

• Read Alford etc. regarding slab models for generation of near-inertial internal waves. Determine f from wind-field, strength of wave generation based on how much the wind-field changes (direction and magnitude). Should be able to find a filter to get these signals to stand out.
• Observe CW spectrum of winds to get rough estimate of input strength.
• Look at mid-depths (upper canyon), and near bottom (both shelf and canyon) for supplemental evidence of how these events affect the near-inertial signal.

from internal_waves_barkley_canyon.

Reorganised into new issues (this will be kept for specific reference).

from internal_waves_barkley_canyon.