The theory of electromagnetic Remote Sensing to random sea waves
Chang Man
Research Institute No. 207 Ministry of Aero-space industry
P.0.Box 142-207, beijing China
Kuang Kui
Depart of Filming Bejing TV Station
Abstract
This paper describes stochastic Green function method in solving random wave equation of electromagnetic field. The volume scattering coefficients of the sea surface of containing bubbles are given. Also when incident angle is less then 300 is pointed out. The surface scattering model is not sufficient. The surface scattering model is not sufficient. The joint problem of volume scattering and surface scattering coefficient in the neighbor hood of incident angle 30° is discussed.
Introduction
In theory of electromagnetic remote sensing, we are concerned about scattering problem of electromagnetic wave, and the interactive medium is the inhomogeneous medium with random rough surface.
The scattering coefficients of electromagnetic wave contain two parts: the first is the surface scattering coefficient; the second is the volume scattering of inhomogeneous medium. At present, there are many methods to calculate the surface scattering coefficients. For example, two-scale model, when incident angle is 30°<
q< 80°, at case of down-wind, used to this model, the theoretical results are basic agreement with experimental data. When incident wave near vertical direction, Rich K. Moor (1979)show out the two-scale model that is not used. Because, in this case, the electromagnetic wave is incident on white caps and bubbles of sea waves. For this case, the two-scale model is not applied, and in the case of upwind, the surface scattering coefficient consists with experimental data to be very poor. This result is the same season. In general, the theoretical result of surface scattering then experimental data is big 8dp.So,if we attempt to improve the theoretical result of the scattering coefficients, we must consider affect of the bubbles in sea waves to dielectric coefficient of sea water, and must use new model-the volume scattering model. On this field, A. K. Fung (1981)and J.A.Kong (1985) had made an important study. Especially, J.A.Kong(1985)used matrix equation to study scattering coefficients to plane surface layer of containing bubbles of different shape and size. For the inhomogeneous medium, in general, Born approximation or Dyson equation method was used. The advantage of these methods is simple in mathematics. In this paper, we used average field method to give random differential equation of scattering field, then, to solve it by stochastically Green method and to give
Out expression of the volume scattering coefficients, and to make numerical calculation on the near vertical incident direction. In discussion we have given out weight joint formula and numerical results of the volume scattering and surface shuttering coefficients in the neighbor hood of incident angle 30°
