Results 191 to 200 of about 4,169 (241)

Study on NPS Evaporation Duct Model

2010 6th International Conference on Wireless Communications Networking and Mobile Computing (WiCOM), 2010
Over the ocean, there is mutual effect between air and sea. This effect would affect atmospheric refractivity, or modified atmospheric refractivity, and a lot of kinds of the profiles of atmospheric refractivity and modified atmospheric refractivity will happen.
Ning Zhang, Nan Li, Bin Tian, Hao Cha, Mo Zhou   +4 more
openaire   +1 more source

Uncertainty quantification of propagation in evaporation ducting

2016 URSI International Symposium on Electromagnetic Theory (EMTS), 2016
The Fourier split-step method is used for solving parabolic equations in, for example, computational electromagnetics. In this paper we develop a spectral based Fourier split-step method that will take a limited degree of information with regard to the refractive index of the atmosphere into account.
M. Enstedt, N. Wellander
openaire   +1 more source

Transhorizon radiowave propagation due to evaporation ducting

Resonance, 2006
A detailed description of evaporation ducts and their relevance to radiowave propagation over the sea has been presented. The constantly changing weather conditions over the sea mean that marine and coastal environments, in particular, are prone to these unusual tropospheric phenomena that facilitate radio waves to have higher signal strengths and to ...
Gunashekar, S. D., Siddle, D. R., Warrington, E. Michael   +2 more
openaire   +2 more sources

Understanding Evaporation Duct Variabilities on Turbulent Eddy Scales

Journal of Geophysical Research: Atmospheres, 2022
AbstractEvaporative Ducts (ED) are common refractive features that exist due to the persistent/strong vertical moisture gradient inherent to the lowest 10s of meters of the marine atmospheric surface layer (MASL). The ED plays a large role in the propagation of signals from the surface‐ or ship‐based radar/communications systems due to the ducting of ...
K. B. Franklin, Q. Wang, Q. Jiang, L. Shen   +3 more
openaire   +1 more source

Tracking atmospheric ducts using radar clutter: evaporation duct tracking using kalman filters

2007 IEEE Antennas and Propagation Society International Symposium, 2007
This paper addresses the problem of tracking evaporation ducts in marine environments. The method tracks the evolution of the range and height-dependent index of refraction using the radar sea clutter. A split-step fast Fourier transform (FFT) based parabolic equation (PE) approximation to the wave equation is used to compute the clutter return in ...
Caglar Yardim, Peter Gerstoft, William S. Hodgkiss   +2 more
openaire   +1 more source

Retrieving evaporation duct heights from measured propagation factors

IET International Conference on Radar Systems 2007, 2007
The knowledge of refractivity is very important for coverage prediction. This problem is common above sea, where the particular atmospheric conditions lead to atmospheric ducts which strongly modify the range of the radar compared to the standard atmosphere coverage. The most common duct which is almost always present is the evaporation duct.
R. Douvenot, V. Fabbro, H.H. Fuchs, H. Essen, C. Bourlier, J. Saillard, Y. Hurtaud   +6 more
openaire   +2 more sources

Polarization dependence of transient signals in evaporation ducts

Radio Science, 1978
The evaporation duct model used is that of Kahan and Eckart and consists of a discontinuous drop of the otherwise constant relative permittivity at the upper duct boundary. The earth is assumed to be a perfect conductor and ideally plane. We determine the electrical field strength exactly at some fixed point within the duct layer, having chosen a ...
H. Zimmer, K. J. Langenberg, K.‐D. Becker   +2 more
openaire   +1 more source

MMW propagation in warm water evaporation ducts

2013 US National Committee of URSI National Radio Science Meeting (USNC-URSI NRSM), 2013
This paper focuses on Ka-band (35 GHz) propagation in maritime evaporation ducts using M-profiles derived from high resolution radiosonde observations from locations with warm sea surface temperature (> 25°C) and large M-deficits (ΔM > 60 M-units), and the equivalent ln-linear model fits to the radiosonde M-profiles.
openaire   +1 more source

Application of Laser Technology in Evaporation Duct Detection

Applied Mechanics and Materials, 2011
Aiming at how to detect evaporation duct environment accurately in real time, method of detecting atmospheric duct by using laser technique was put forward. From the model of air refractive index of radar band, theoretical relationship between laser scattering properties of aerosol over the ocean and vertical change characteristics of the air humidity ...
Le Dong Wang, Jian Gan Wang, Tao Liu
openaire   +1 more source

Evaporation Duct Communication: Test Plan Part 2

1991
Abstract : This document is a continuation and expansion of an earlier study that examines the feasibility of using the evaporation duct to support an alternative high-speed communication system for Navy applications. This Evaporation Duct Communication (EDCOM) experiment is a unique opportunity to evaluate another communication channel that can ...
L. T. Rogers, K. D. Anderson
openaire   +1 more source