These values grouped around 40 ~ 60 percent relative humidity.
This is evidence
nt
that the portion of the cloud traversed does not contain liquid water in sufficie
amount to entertain any speculation about creating rain by artificial seeding, at
least in the tropics.
2.
WIND MEASUREMENT
a.
The wind measurement project of this program was designed to measure
the wind produced by the rush of surface air into the rising column of hot gases
produced by the rising fireball.
‘The magnitude of such 4 draft wind on the area
surrounding the blast has never before been measured, and has been the subject of
considerable speculation,
Twenty-five pitot type wind measuring instruments of
standard design were medified for this type of measurement and were partially successful in obtaining “order of magnitude" results.
One new and untested ansmometer
of the hot wire type, and another of the strain gauge type, were also tested for
suitability in this type of service.
b.
Useful afterwind data were not obtained on DOG shot due to the -paraly—
sis of the recording devices by the negative or suction phase of the blast which
obscured a majority of the afterwind obtained.
The results of this test, however,
led to modifications of the instruments.
c.
On EASY shot the magnitude of the surface component of the afterwind
was found to be considerably less than anticipated, and measured from 26 to 32 miles
per hour (including normal surface wind component) at distances from 1,200 to 2,300
yards.
The duration of the afterwind was found to be approximately 15 seconds after
passage of the shock wave at this location,
This indicates that the large quantity
of air which rises in behind the fireball is drawn from its immediate vicinity, and
that a chimney action from ground level is not sustained for any appreciable length
of time,
d,
On the third (GEORGE) shot, three instruments yielded records at 1,260,
4,750 and 7,870 yards respectively.
Although the pitot tube was destroyed on the
recorder at 1,260 yards, the direction record indicated that for this large shot the
afterwind phase lasted for 5 minutes at this position.
The afterwind effects at the
greater distances (indicated largely by alternation of wind direction) lasted only
l2 and 7 seconds respectively, with minor changes of wind speed of 2 to 6 miles per
hour,
C.
It would appear, from the meager results of this test, that any large
afterwinds which might result from the rising fireball. must be confined to a radius