Accession Number : ADP006168

Title :   A Forecasting System Using the Parabolic Equation Application to Surface-to-Air Propagation in the Presence of Elevated Layers,

Corporate Author : RUTHERFORD AND APPLETON LABS CHILTON (UNITED KINGDOM)

Personal Author(s) : Craig, K. H. ; Levy, M. F.

Report Date : SEP 1989

Pagination or Media Count : 13

Abstract : The parabolic equation approach to clear-air propagation modelling overcomes many of the difficulties associated with ray and mode theory methods. A parabolic equation model has been implemented on a PC based system using a transputer to carry out the computationally intensive numerical integrations. The model has been used from VHF to millimetric frequencies and applied to evaporation duct and elevated duct problems. The latter are important for surface-to-air propagation and have been difficult to solve because of the complicated structure of the layers. A case study of an elevated duct caused by anticyclonic subsidence shows the importance of up-to-date meteorological data from a wide geographical area. A full-wave calculation of the wideband properties of the propagation channel illustrates the possibilities opened up by the new model. The frequency selective effects can be large, and are sensitive to the small-scale structure of the ducting layers.

Descriptors :   *ELECTROMAGNETIC WAVE PROPAGATION, *SURFACE TO AIR, *FORECASTING, TROPOSPHERE, ANTICYCLONES.

Subject Categories : Radiofrequency Wave Propagation

Distribution Statement : APPROVED FOR PUBLIC RELEASE