Altitude Wind Research Articles

Probe Microphone Testing at High Temperatures and High Intensities

A microphone using a resistively terminated probe tube of the type described by R. W. Leonard [J. Acoust. Soc. Am. 24, 113(A) (1952)[ has been developed. This microphone was designed to facilitate the measurement of sound pressures at the wall surface of jet engine test cells and altitude wind tunnels and, therefore, attention was focused on the problems of obtaining satisfactory performance with the probe tip exposed to: (1) high temperature gases; (2) high sound pressure levels; (3) reduced static pressure of simulated altitude. Techniques have been worked out for measuring the flow resistance of the probe tube tip at temperatures up to 900°F. A resonant tube system has been used to obtain sound pressure levels up to 175 decibels for the purpose of rank ordering various probe tube tip materials according to their total harmonic distortion. A low pressure cavity enclosing a sound source and monitor microphone was used for measuring the mid-frequency sensitivity of the probe microphone system with static pressures from 1.0 to 0.2 atmosphere at the probe tip. An approximate electrical analog circuit of the probe tube microphone system provides a basis for using the results of these tests to predict the probable behavior of the microphone under simultaneous high temperature, high intensity, and low static pressure conditions. This work was supported by the U. S. Air Force under Contract No. AF33(600)-23807.

Some Measurements of Velocity of High Altitude Winds at Sydney, NSW

A technique is described of measuring wind velocities at high altitudes by observing with radar the course of an ascending balloon. The results of high altitude windfinding experiments conducted at Sydney during the winter months of 1949 showed a maximum velocity at 40,000 feet and a minimum at about 70,000 feet. The flow near and above the maximum was generally from the west. At higher altitudes, near the minimum, the wind was also from the west but showed a tendency to change to the east during July and August.

A radio echo method for the investigation of atmospheric winds at altitudes of 80 to 100 km

The effects of high altitude winds on the ionized trails produced by meteors are discussed. The variations of wind velocity with height between altitudes of 80 to 100km can be determined from the fluctuations in amplitude and the changes in width of the radio echoes from the trails. These vriable winds are present at all times in the meteor region, and the velocities at points separated by only 5 to 10 km may differ by as much as 50 m/sec. Uniform wind velocities can also be measured by observation of the steady drifts in range of long duration echoes. These uniform winds also have velocities of the order of 50 m/sec. A reversal in the predominant wind direction is observed between 0100 and 0200 hrs local time, the direction prior to 0100 hrs being roughly from North to South, and after 0200 hrs from South to North.

LXII. The influence of high altitude winds on meteor trail ionization

Abstract The paper contains a discussion of the possible effect of high altitude winds on the ionized columns created by meteors. It is shown that the various types of range drifts observed in the long duration radio echoes from meteor trails can be explained in terms of the influence of winds on the ionized column. A comparison of the characteristics of the fading of the radio waves returned from the ionosphere, with the characteristics of the fluctuations of the radio echoes from meteor trails, leads to the conclusion that some of the ionospheric phenomena may be due to meteor ionization in the E region.