Vertical motion in the atmosphere and its effect on VHF radio signal strength

Abstract

The hypothesis is proposed that the vertical gradient of the refractive index is strongly affected by the vertical motion in the atmosphere. It is shown that changes in this gradient are due principally to changes in the moisture stratification and temperature lapse rate resulting from the vertical velocity and its horizontal gradient within the air mass. Mean radio signal strengths are plotted against the time position of 500‐mb troughs and ridges relative to the radio link. A series of 500‐mb charts is given, with the vertical velocity field obtained by the Sawyer‐Bushby method. The vertical velocity over two radio links is compared with the signal strength. Cross‐sections taken through several of the troughs illustrate the stratification changes on the forward and rear sides of the troughs due to vertical motion.

A radiometeorological study, part I. Existing radiometeorological parameters

“….N, between Ns and N I wher e NI is the value of (n -l ) 10 6 at a height of 1 Ian. Other groups have studied differ ent par ameters [Misme 1960a, b , and c;Flavell and L ane, 1962 ;Moler and Arvola, 1956;Moler and Holden, 1960], eit her as possible alternatives to Ns and t ::. .N in the prediction process or as quant ities which clarify the effect of meteorological features, such as anticyclonic subsidence, on signal strength.…”

Tropospheric scatter propagation and atmospheric circulations

“…Misme [11], using a weighted average tropospheric refractivity, found correlation between this "useful gradient" and the received signal. Time-averaged low-level refractive gradients have been shown by Moler and Arvola [12], to be principally a function of the large-scale vertical motions in the atmosphere. Later in this report, computations of convergence at the 300-millibar (mb) level and the implied subsidence (see app.…”