Microwave scattering by tropospheric fluctuations in an evaporation duct

Abstract

Numerical analysis of the centimeter wave propagation in an evaporation duct with allowance for scattering by correlated turbulent fluctuations of the tropospheric refraction index is carried out. It is shown that energy leakage from the duct leads to an additional decrease in the average wave power. The amplitude of random power variations above the duct turns out to be significantly higher compared with the variations inside the duct. An increase in the vertical correlation radius of refraction-index inhomogeneities leads to an increase in the vertical correlation radius of the radio-wave intensity.

A Four-Parameter M-Profile Model for the Evaporation Duct Estimation From Radar Clutter

“…4) The profiles described by this one-parameter model have very long tails in the very lowest height levels (see Figure 4), i.e., the modified refractivity near the surface varies very fast by logarithmic law, leading to anomalously high gradients of M , which cause deflections of radio waves to large angles from the horizontal direction and preclude propagation to large distances [17]. Therefore, the logarithmic law is potentially no longer fulfilled at very small heights.…”

“…In Refs. [17,19], it was shown that the approximation of the vertical profile at a height of less than 2 m by a tangent straight line is quite good.…”

Applying the Parabolic Equation to Tropospheric Groundwave Propagation: A review of recent achievements and significant milestones

“…This study verified that the turbulent fluctuation influences the choice of radar parameters, such as propagation frequency and antenna site, in actual calculations. In 2009, focusing on the drawback that single-mode analytical calculation could get accurate results just in long-range propagation, Ivanov et al [87] studied the scattering and radiation leakage problem resulting from turbulent fluctuation by PE numerical calculation. It achieved verification by centimeter-wave experimental measurement and summed up the four characteristics of the field distribution: 1) nonuniform leakage of radiation on the distance 2) additional attenuation of radiation on the distance 3) increased amplitude of the field-intensity fluctuations above the duct compared with the fluctuations inside the duct 4) the occurrence of vertical correlations of the field intensity when the finiteness of the vertical correlation radius of inhomogeneities is taken into account.…”

Brief review on PE method application to propagation channel modeling in sea environment

“…Equation (20), however, has been obtained assuming thermally neutral troposphere stratification and does not account for the tropospheric stability effects on the M profile [7,29,33]. Attempts at improving (20) have been made by changing the slope in different parts of the log-linear curve [116,117], thus making it to better fit the experimental profiles and, hence, include the influence of tropospheric stability. Recent efforts of the US Naval Postgraduate School to develop a state-of-the-art bulk evaporation duct model (referred to as NPS model) based on measured (or modeled) values of wind speed, air and sea temperature, relative humidity and atmospheric pressure have led to restoration of high-fidelity profiles and evaporation duct heights [118].…”