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Simulation of tidal current components and oil spills spreading from Radarsat
Maged Marghany International Institute For Aerospace Survey and Earth Science (ITC) Division of Applied Geomorphological Surveys PO Box 6, 7500 AA Enschede, The Netherlands magedupm@hotmail.com, maged@itc.nl Abstract
This paper presents work done utilizing Radarsat fine mode data to model the tidal current component effects on oil spills spreading. In this study, the utility of oil spills detection is examined using fractal dimension methods. The finite difference model is used to simulate the tidal current velocity from Radarsat data. The tidal current velocity modeled by using a finite difference model of Doppler shift frequency. The current velocity components are modeled by applying Lagarangian interpolation. The statistical model is used to find out the significant correlation between tidal current components and oil spills spreading. The results show the tidal current components have effects on the oil spills spreading. The northward tidal current components are effected the length of the oil spills while the eastward components are effected the width of oil spills. In conclusion, Radarsat data has good potential for oil spills detection and mapping. Radarsat data could be used to model the tidal speeds and their effects on oil spill patterns. The tidal current components are in good correlation with oil spill lengths and widths. Introduction Modeling of oil spills movements by remote sensing is in early stage of investigation. Up to now the scientists could not be used the full capability of remote sensing techniques for modelling and predicting oil spill movements. Using remote sensing techniques for oil spill detection was just focused on the improvement of detection algorithms. These studies cannot provide any sufficient information for identification the effects of physical parameters (wind, current, waves…etc.,) on the oil spill patterns.  fig1 This study aims to model the effect of tidal current components on oil spill patterns (width and length) on Malacca Straits. This is because of the fact that tidal current movements considered significant in narrow waterway such as the Malacca Straits, which is a near 12 hourly sinusoidal phenomenon arising from the semi-diurnal motion of the M2 and S2 tidal components. Methodology Study Area The study area is located in the Malacca Straits between 102° 16' E to 103° 48' E and 1° 16'N to 2° 13' N. According to Wyrtki [5] the water movements are in general directed towards the northwest direction and are strongly related to the surface gradient of the sea level. Furthermore, Wyrtki [5] stated that the period of strongest flow is from January to April, during the northeast monsoon with current velocity of 0.95 m/s.  fig2 According to Benelli and Garzelli [1] the fractal dimension could be estimated from power spectra. This means that fractal dimension can be characterized by a random-phase Fourier description in the form of power density. The power density can given by P (W1,W2) = 1/[ÖW12+W22]b (1) where W is the frequency domain of the Fourier Transform and b= 2H +2 as H is Hurst or persistence parameter, controlling the roughness of the surface. H is 1 corresponding to smooth surface and H is zero which corresponding to a very rough texture. The fractal dimension D and persistence parameter are related by D = 3-H (2) Thus D can be computed by applying a linear regression on log [P(W1,W2)] vs. Log [ÖW12, ÖW22]. Furthermore, H can be computed from the linear regression of ratios of powers.
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