Study of characteristics of sea clutter is very important for signal processing of radar, detection of targets on sea surface and remote sensing. The sea state is complex at Low grazing angle (LGA), and it is difficult with its large irradiation area and a great deal simulation facets. A practical and efficient model to obtain radar clutter of dynamic sea in different sea condition is proposed, basing on the physical mechanism of interaction between electromagnetic wave and sea wave. The classical analysis method for sea clutter is basing on amplitude and spectrum distribution, taking the clutter as random processing model, which is equivocal in its physical mechanism. To achieve electromagnetic field from sea surface, a modified phase from facets is considered, and the backscattering coefficient is calculated by Wu’s improved two-scale model, which can solve the statistical sea backscattering problem less than 5 degree, considering the effects of the surface slopes joint probability density, the shadowing function, the skewness of sea waves and the curvature of the surface on the backscattering from the ocean surface. We make the assumption that the scattering contribution of each facet is independent, the total field is the superposition of each facet in the receiving direction. Such data characters are very suitable to compute on GPU threads. So we can make the best of GPU resource. We have achieved a speedup of 155-fold for S band and 162-fold for Ku/Χ band on the Tesla K80 GPU as compared with Intel® Core™ CPU. In this paper, we mainly study the high resolution data, and the time resolution is millisecond, so we may have 10,00 time points, and we analyze amplitude probability density distribution of radar clutter.
When the electron plasma is blown from the solar wind and enters into the earth atmosphere, a large number of neutral particles are excited to cause the significant event called aurora phenomenon. In this process, there are several sources of excitation including electron impact, dissociative recombination, thermal electron excitation. Particularly, auroral optical radiation produced by electron impact on oxygen atoms is investigated to explore the relationship between secondary electron energy and spectroscopic emission features. Based on the ground observations of aurora spectral images, the emission characteristics reveal the primary electron energy and flux, the basic atmosphere of species concentration and electron temperature, abundant information of the deposited particles. With the consideration that the radiations of atomic oxygen 5577 Å and 6300 Å are representative auroral spectral lines, we use numerical calculations of relative intensity ratio I(λ5577)/I(λ6300) for various energies to approximate the true ratio. A theoretical primary energy is then determined and used to estimate radiation features at other spectral bands. The best approximated primary characteristic energy is determined as 0.585. The estimated pixel lines of λ6300 and λ6364 underestimate with a factor ranging from 0.95 to 2.2 and from 0.92 to 1.41, respectively.
The propagation of millimeter wave through offing fog is affected by the size distribution, droplet shape, dielectric
parameters and frequency. Based on the Gamma distribution of droplets size, the property of offing fog is analyzed.
Using the Monte Carlo method to establish the propagation model, the propagation process of millimeter wave is
simulated at different frequencies. The transmission and attenuation of millimeter wave through offing fog at different
frequencies （35、94、140、220GHz） and different sea conditions is obtained which can reflect the influence of
offing fog on the propagation of electromagnetic wave.
The vector radiative transfer (VRT) theory for active microwave remote sensing and Rayleigh-Gans approximation
(GRG) are applied in the study, and an iterative algorithm is used to solve the RT equations, thus we obtain the zeroorder
and first-order equation for numerical results. The Michigan Microwave Canopy Scattering (MIMICS) model is
simplified to adapt to the crop model, by analyzing body-surface bistatic scattering and backscattering properties
between a layer of soybean or wheat consisting of stems and leaves and different underlying soil surface at multi-band
(i.e. P, L, S, X, Ku-band), we obtain microwave scattering mechanisms of crop components and the effect of underlying
ground on total crop scattering. Stem and leaf are regard as a needle and a circular disk, respectively. The final results are
compared with some literature data to verify our calculating method, numerical results show multi-band crop microwave
scattering properties differ from scattering angle, azimuth angle and moisture of vegetation and soil, which offer the part
needed information for the design of future bistatic radar systems for crop sensing applications.