| Synthetic aperture radar(SAR)plays a major role in the observation of oil spills which has the advantage of high efficiency,real-time and not being disturbed by clouds and rain.At present,research about SAR oil spill monitoring mainly focuses on the identification of oil spills and suspected oil spills,and there are few studies on the influence of emulsification process on oil film microwave scattering characteristics.In this paper,the microwave scattering characteristics of crude oil emulsification were studied by carrying out the crude oil emulsification observation experiment with C-band fully-polarized scatterometer.Combining airborne hyperspectral imaging spectrometer and 3D laser scanner observation data,it is expected to provide data support for the SAR monitoring of crude oil emulsification and the reasonable assessment of oil spill volume.The main research contents are as follows:(1)Research on the effect of emulsification on the normalized radar cross section(NRCS)of crude oil.(2)Based on the measured oil film roughness and moisture content,simulate NRCS of oil film during the emulsification process use the theoretical model of scattering and compare it with the measured data to explore the scattering mechanism of crude oil emulsification.(3)Research on the sensitive parameters of microwave scattering that reflect the degree of crude oil emulsification in the process of quantitative crude oil uniform emulsification by analyzing the changes in backscattering difference((35)?~0)between oil and water,damping ratio(DR)and co-polarization ratio(CPR).(4)Research on the relationship between the oil film thickness and the sensitive parameters of microwave scattering in the emulsification process based on the observation data of quantitative crude oil uniform emulsion;Based on the combined observation data of scatterometer and hyperspectral imaging spectrometer in the natural emulsification observation experiment,establish and verify the empirical relationship between oil film NRCS and oil film thickness.(5)Using space-borne SAR satellite images,the selected sensitive parameters of crude oil emulsification and empirical formula of oil film thickness under natural oil spill conditions were applied to the monitoring of marine oil spill case.The main conclusions are as follows:(1)It is found that the formation of emulsion will change the microwave scattering characteristics of crude oil,and the emulsification will increase the NRCS of crude oil to a certain extent.(2)The measured surface roughness and water content of the oil film are used to simulate the oil film NRCS based on the scattering theory model,and the backscattering mechanism of crude oil emulsification was explored.The change of NRCS is modulated by the oil film dielectric constant and surface roughness,and the influence of the dielectric constant is dominant factor.(3)Based on quantitative crude oil uniform emulsification data,it is found that(35)?~0,DR can reflect the changes in the degree of emulsification to a certain extent,which was best at the VV polarization mode.(4)An empirical formula of oil film thickness is initially established under the condition of natural oil spill of which oil film was mixed with both crude oil and emulsified oil,and the formula shows that the thickness of oil film increases with the decrease of(35)?~0.(5)Using spaceborne SAR satellite image data,the sensitive parameters of crude oil emulsification(35)?~0,DR and the empirical formula of oil film thickness which constructed under natural oil spill conditions were applied to the marine oil spill case,successfully explained the distribution of the relative thickness of the oil film(heavy oil)and emulsification characteristics,and provided experimental parameters and method support for accurate marine oil spill remote sensing monitoring. |
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