Dennis B. Trizna
Naval Research Laboratory
a. Determine the spatial morphology of the offshore bar by comparing averaged radar sea scatter images of enhanced wave breaking over the bar with video image estimates of the same, and with measured bottom profiles. Qualitative comparisons of radar derived bar locations have been made in past, but no systematic comparisons have been made on a synoptic basis. (Trizna, Hathaway, Whalen, 1993 AGU Fall Meeting).
b. Remotely estimate the directional distribution of wind waves locally within the surf zone and beyond using 2D-FFT analysis of individual radar images. These techniques are currently being used in offshore locations in deep water, but have never been quantitatively tested in the nearshore region. A capability to determined wave refraction will be developed from water wave spectral peak azimuthal shifting with water depth using such radar image analysis.
c. Remotely estimate the presence and wave frequency of infragravity (IG) waves by 2D-FFT analysis of 2.4-s sequential radar images, and compare with in situ seismic sensors. The nearshore depth variation has been observed to modulate the intensity of wave crest radar cross section (RCS) due to nearshore depth variation due to the IG wave passage along shore (Trizna, et al, ibid).
d. Develop an empirical relationship between the marine radar wave crest echo RCS statistics and the spatial distribution of turbulent kinetic energy (TKE) generated at the surface boundary layer associated with wave breaking. Ground truth comparisons of TKE production and dissipation will be made with insitu measurements from other investigators.
e. Determine utility of using shore based radar offshore look vs pier mounted radar inshore illumination of breaking waves to locate bar and measure surface wave directions.
Use marine radars mounted on the end of the pier tower and at locations shoreside of the dune to collect radar imagery. Radar scattering processes as seen from two different aspects have not been compared previously. While objectives 1-4 have been qualitatively accomplished previously, offshore/inshore comparisons of same have never been made. The marine radar will collect synoptic data around the clock, as it is unaffected by visibility effects due to rain or darkness.