ON THE FREQUENCY OF RETURNING ACOUSTIC RAYS AND FOCUSING FOR HUNTSVILLE AND MISSISSIPPI TEST FACILITY.
ARMY MISSILE COMMAND REDSTONE ARSENAL ALA PHYSICAL SCIENCES LAB
Pagination or Media Count:
The problem of acoustic focusing by returning sound rays from the atmosphere in the Huntsville and Mississippi Test Facility is analyzed in this report. First, an objective criterion to determine focusing by computer methods from the atmospheric data and the derived sound speed profile is presented. Afterwards, the empirical probability of focusing is derived for four seasons for the event of a test firing, as a function of the azimuth and with its areal distribution. In short, returning rays in the afternoon hours can be expected in 25 percent of the firings in summer and 90 percent in winter however, focusing chances are 10 percent in summer and 50 percent in winter. The azimuthal variation ranges from around 60 percent for easterly to 5 percent for westerly directions in wintertime and reduces to 10 to 1 percent, respectively, in summer. Average chances for focusing encountered by isolated targets of limited areal extent may be as high as 20 percent in wintertime, while they stay below 5 percent in summer. The wind influence is considerably higher than commonly assumed. Practically all focusing in summer can be attributed to the superposition of the wind profile upon the temperature profile. Only 10 to 15 percent of focusing in the winter afternoon hours is caused by the structure of the temperature profile inversions. Author
- Atmospheric Physics