COHSTREX 2006 Microwave Remote Sensing Measurements


In July, 2005, our group deployed our continuous-wave Riverscat system on the barge alongside Andy Jessup's IR instruments. We also deployed our pulsed Doppler radar, RiverRad after some modifications, at the Rinker's Asphalt Plant across the Snohomish River from the tip of Jetty Island. In July, 2006, we deployed these same two instruments in the same locations and also flew our CORAR airborne Doppler radar on a DeHavilland Beaver rented from Kenmore Air.

Analysis of Riverscat output in the form of Doppler spectra and currents is in the process of being compared with currents measured from the IR imagery.

RiverRad data from 2005 have been converted to imagery and have shown several interesting features in the flow patterns of the Snohomish River at various stages of the tidal cycle. Examples are displayed in Figures 15-17.

Figure 15. Turbulence downstream of the sill at the north end of Jetty Island. The red dot in the lower left plot shows the phase of the tide when the image was collected.

Figure 16. Increased radar backscatter at the front between the main channel water and water from the overflow channel.

Figure 17. Two parallel streaks of enhanced backscatter at low tide. Possibly associated with the dredged channel.

Figure 18 shows an overview of the study site and RiverRad deployed at the asphalt factory in 2006.

Figure 18. Photo (right) of the site of the COSHTREX measurements taken from the beaver. The barge with the IR and microwave equipment is in the lower center just off the north tip of Jetty Island. The sill was exposed at this time. The ship in the channel contains the WHOI equipment. RiverRad was set up just off the picture to the left of the pilings seen in the top left. The photo on the right shows RiverRad deployed at the asphalt factory in 2006.

Data collected in this year have not all been converted to images yet. An example of some images from data collected early in the experiment is shown in Figure 19 where the dual streaks and/or frontal features seen in 2005 again appear to be present.

Figure 19. Images from the RiverRad 2006 deployment. Left are cross sections, right are the corresponding radial velocities.

Figure 20 shows CORAR as deployed on the Beaver in 2006.

Figure 20. CORAR deployed on the DeHavilland Beaver.

On the second day of flights, the microwave power amplifier failed and the flights were terminated. We therefore have data only for July 11, 2006. Images of cross sections at vertical and horizontal polarizations for one of these flights are shown in Figure 21.

Figure 21. Preliminary cross section images of Jetty Island and the surrounding river taken on July 11, 2006 at two different times. Images on the left are VV polarization. Those on the right are HH. South is up, Jetty Island is at about 3 km along track, and the row of pilings runs from 3.2 to 3.8 km along track and 900 to 700 m in ground range.

Analysis of data from both years is continuing. We want to complete the comparison of Riverscat surface velocities with those from the IR in the near future and compare the features seen in the RiverRad imagery with models after that. We will also process and analyze the single day of CORAR data as completely as possible.

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