Ecoinformatics Problems of the World Ocean - New Ecoinformatics Tools in Environmental Science: Applications and Decision-making - page 264

techniques based on microwave radiometry allow to determine the oil pollution of
the water surface under arbitrary weather conditions.
An extensive application of remote sensing techniques depends on the knowledge
of the processes of interaction between oil and sea water, its optical and electric
characteristics, the impact of the atmosphere and other factors on the propagation of
electromagnetic waves. The combination of microwave and IR (infrared) ranges with
mathematical modeling techniques is an effective method to discover oil spills on the
water surface. The distinction between the emittance and the temperature of polluted
and fresh water surface areas is the physical base for the remote sensing of oil spills by
means of microwave

— and IR — radiometers. The emittance j of the three-layer

system atmosphere-oil-water having smooth boundaries of the sections can

be calculated with formulae suggested by Kondratyev et al. (1996). Figure 4.2

gives an example of the dependence of the emittance variations

ʱ

Dj for the

atmosphere-oil-water system as a function of the oil spill thickness .

The oil spill dielectric properties occupy an intermediate position between free
space (atmosphere) and water. As a result, the arising of a

ʱ

film leads to the effect of

medium co-ordination (to the decrease in the re cient) and to the

growth of the surface radiobrightness temperature. As the oil

fl ection coef

film thickness

ʺ

increases, the value T Y = first increases, but

then an interchange of maxima and minima is observed. From Fig. 4.2 it is obvious
that it is necessary to simultaneously measure the radiobrightness temperature by
means of radiometers with different wavelengths in order to remove the uncertainty
in the

T 0 (T 0 is the surface temperature) at

film thickness determination.

films, arising under small volumes of spilled oil or in the near-boundary
area of the oil spills, do not change the emittive ability of a smooth water surface in

Thin

Fig. 4.2 The emittive ability of oil spills having different thickness (Mitnik 1977). Wavelengths
(in cm) given on the curves. The water temperature is 10 ° C and the oil dielectric permeability ʵ is 2.2