||Our main research is devoted to application of the weak hydrodynarnic theory to study the shallow water topography. This theory allows us to connect bottom topography, current fields and radar backscattering intensity. We used the SAR (Synthetic Aperture Radar) image of the ocean to analyze the relation between depth variations and image intensity for Taiwan Tan area in the Southern Taiwan Strait, Additionally, we discuss the effect of advection term in the theory. First, we choose 4 test areas, three areas have distinct alternating darken and lighter bands on SAR image. The fourth one is without these features. We compute the variation of image intensity along a test line cutting in each area. For theoretical model, average depth and simulated current field provided by Central Weather Bureau and corresponding constants were used. Finally the variation of depth (d) were found from experimental data on variations of SAR image intensity. Lacking of detailed depth profiles did not allow us to carry out comparison of derived d values with real data. However, retrieved d values are in the range of observed depth variations in the Taiwan Tan. To tune the model for Taiwan Tan area, it is necessary to get more detailed map for test area and get new SAR image at favorable atmospheric (2 m/s < wind speed < 7 m/s) and oceanic (current velocity > 0.5 m/s) conditions.|
We found that it is possible to connect the image intensity and water depth using the published theoretical model. Both the range of depth variability (12m to 61m) and the average retrieved d are close to available measured data. Besides, there is a good slope correlation between the retrieved d and measured depth in test area 3. Variety of underwater relief is observed in Taiwan Tan area. Thus it is necessary to conduct detailed depth measurements for 2-3 test areas. This data will allow to tune the theoretical coefficients or to advance the theory. Posteriorly, it can serve as a basis for construction of detailed bathymetric map for the whole area and arrange monitoring of depth variations with SAR.