J. Europ. Opt. Soc. Rap. Public. 8, 13051 (2013) www.jeos.org Optical contrast of oil dispersed in seawater under windy conditions Z. Otremba zotremba@am.gdynia.pl Gdynia Maritime Univ., Physics Department, Gdynia, 81225, Poland O. Zielinski Univ. of Oldenburg, Institute for Chemistry and Biology of the Marine Environment, 26111 Oldenburg, Germany C. Hu Univ. of South Florida, College of Marine Science, St. Petersburg, FL 33701, USA Oil pollution of natural waters represents a serious threat for aquatic ecosystems, and the assessment of the degree of pollution requires measurement strategies including remote sensing and modeling. While surface oil pollution is relatively easy to detect with radar or optical remote sensing, underwater oil emulsions can only be detected using visible light as an information carrier. Here the Michelson contrast of sea area polluted by an oil-in-water emulsion under various wind conditions is simulated through Monte-Carlo modeling. The results show the premise for optimal direction of observations in which the possibility of detecting the emulsified oil is maximized. [DOI: http://dx.doi.org/10.2971/jeos.2013.13051] Keywords: Air-sea interactions, oil pollutions, radiative transfer, Monte Carlo method, remote sensing reflectance 1 INTRODUCTION Optical remote sensing provides a valuable tool for synoptic and long-term observations of natural water masses. The re- motely sensed water-leaving radiance, after normalization to the incoming irradiance, carries information about the vari- ous water constituents. Such information is often interfered by frequent sun glint on the sea surface [1]. On the other hand, the presence of sun glint also facilitates observing surface oil films [2]. The effectiveness of receiving information about the processes taking place in the water column, however, is re- duced with sun glint. In this paper, the possibility of detecting “clouds” of oil-in-water emulsion in the water column is an- alyzed under various conditions using Monte-Carlo simula- tions. The objective is to understand how the various observ- ing conditions may affect the observed reflectance contrast for realistic water environments. 2 METHOD 2.1 Model The deep sea (up to 200 m to eliminate the impact of the seabed light reflection), filled with water characterized by in- herent optical properties (IOPs) as described in Figure 1, rep- resents the environment studied by the model. To study the optical properties of oiled water in the ocean environments, the volume scattering function of Petzold [3] is used, and other IOPs are derived MODIS measurements over the north- eastern Gulf of Mexico where the Deepwater Horizon oil spill occurred between late April and mid July 2010. The cloud of oil emulsion is immersed at 1 m depth. Its thick- ness is 5 m. Solar light falling on the sea surface contains dif- fused sky photons and direct solar radiation at a zenith an- gle of 30 ◦ (Table 1, after the RADTRAN model developed by Gregg and Carder [4]). FIG. 1 Schematic representation of the seawater polluted with an oil-in-water emulsion in the model applied in this paper. Symbols a, b, and VSF refer to, respectively: ab- sorption coefficient, scattering coefficient, and volume scattering function. Parameters a water ,b water ,a oil ,b oil and VSF oil are all dependent on wavelength (Tables 2a and 2b). Received June 10, 2013; Ms. accepted July 03, 2013; published July 29, 2013 ISSN 1990-2573