Abstract
Abstract. This paper addresses the problem of estimating range-varying parameters of the height-dependent refractivity over the sea surface from radar sea clutter. In the forward simulation, the split-step Fourier parabolic equation (PE) is used to compute the radar clutter power in the complex refractive environments. Making use of the inherent Markovian structure of the split-step Fourier PE solution, the refractivity from clutter (RFC) problem is formulated within a nonlinear recursive Bayesian state estimation framework. Particle filter (PF), which is a technique for implementing a recursive Bayesian filter by Monte Carlo simulations, is used to track range-varying characteristics of the refractivity profiles. Basic ideas of employing PF to solve RFC problem are introduced. Both simulation and real data results are presented to confirm the feasibility of PF-RFC performances.
Highlights
The refractive environment is generally characterized by the refractivity profile (N-profile) or the modified refractivity profile (M-profile), and there are many techniques that measure or predict the tropospheric index of refraction
Richter (1969) has pointed out that the temporal and spatial variations of radar echoes are related to the temporal and spatial variations in the layers of the refractivity profile, which motivates the research of atmospheric refractivity estimation from radar clutter returns, i.e. refractivity from clutter (RFC)
A horizontal varying refractive environment is simulated by the idea trilinear duct model and the corresponding synthetic propagation losses at sea level are used to quantify the performance of particle filter (PF)-RFC estimations
Summary
The refractive environment is generally characterized by the refractivity profile (N-profile) or the modified refractivity profile (M-profile), and there are many techniques that measure or predict the tropospheric index of refraction. Conventional methods of the refractive index measurement consisting of detecting height dependence of temperature, pressure and humidity performed by radiosondes, microwave refractometers, or rocketsondes have some drawbacks, such as expensive and/or difficult deployment. These measurements tend to provide estimations of refractivity versus height only at a single range (Halvey, 1983; Weckwerth et al, 2005; Yan et al, 2006; Yu et al, 2009; Cheng et al., 2012).
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