In all major Tt'spects this report (Border,> .I~)S:~) is an excellent
analysis of the probable radar situation during the July 1952, Wa~hington
sightings.
TIle atmospheric conditions in existence at the times of these UFO
incidents, as shown in figs. 13, 14, and IS, are rathcl' peculiar. Refractivity
profile for 19 JUly 2200 LST shows a surface inversion of 1.7°C (3.1°F)
but the resulting refractivity gradient is only -81 km- l , about twice
the "standard" value. 111t>re is a rather unusual subrefractive layer
at 3833 to 43B9 m. produced by overlying moist air. Relative humidity
drops from 84% at surface to 20% at base of this layer, then climb~
to 70"" at top of the layer. A Humber of significant levels are missing
from this profile, which is comn:oJl in 1952 Silver IIi 11 profiles, but even
so it :is indicative of unusualltmosJlh,~ric conJitions. '111e radar sight-
ings were made between 2340 LST allll 0540 LST l.July 2(1), and the atmospheric
stratification was no doubt marl strongly developL~J by that time. Tn
addition, Silver lIill is at an elevat~on of 88 m. (289 ft.) above MSL,
whereas Washington National Airport is at an elevation of only U m.
(43 ft.). The intervening 75 m, is precisely that part of the atmosphere
in which some of the most spectacular super-refractive and ducting layers
would oe expected to develop. In\leed, records for 19ttS-19S0, Juring
which radiosonde upper-air soundings were launcheJ from Washington
National Ail'port, reveal a ml'~h stronger tendency for the fomation of
anonwlous propagation cond./ tions than the Si lver IIi 11 data.
'11H' profiles for 2S ,July and 26 .July, 2200 LST arc 11I0re complete
than the 19 july profile, although some signific.ant leveL; were noted
as missing from the 26 July profile. Otherwise, the f01'er,oing COlfllllE'nts
apply to these profi les as well. The 2~; ,July profi 1e shows ;l SUPC'!'N
refractive' sllrfac{' layer ami a strong dfwnteu duct; there is a ,1.(,°(;
(R.~°F) tl'lll]1cnltllrc inversion through the elevated dw:t. It is perhaps
significant that unidentified rnuar target:: began (Jppcarin~ at 21130 LST
In all major rc'spects this report (Border, •.1~)C;:i) is an ex(:ellent
analysis of the probable radar si tuati,)!) during the July 1952, Wa~hington
sighting;;.
n,c atmospheric conditions in existence at the times of these lIFO
incidents, as shown in rigs. 13, 14, and IS, are rather peculiar. Refractivity
profile for 19 July 2200 LST shows a sllrface .inversion of 1.7°C (3.1°F)
but the resulting refractivity graJient is only -81 km- l , unout twice
the "standard" value. 111l:'re is a rather unusual subrefractive layer
at 3H33 to 4389 m. produced by overlying moist air. Relative humidity
drops from 84% at surface to 20% at base of this layer, then climbs
to 70°" at top of the layer. A Humber of significant levels are missing
from this profile, which is comn:oll in [952 Silver IIi 11 profiles, but even
so it :i.s indicative of unusual It)llosph<!ric conditions. 'J11C radar sight-
ings were made between 2340 LST allll 0540 LST l.1111y 20), and the atmospheric
stratification was no doubt mor r - strongly develo[1lHl by that time. Tn
addition, Silver Hi II is at an elC'vatlon of 88 Ill. (2B9 ft.1 ahove MSL,
whereas Washington National Airport is at an elevation of only U m.
(43 ft.). The intervening 7S m, is precisely that part of the atHiosphere
in which some of the most spectacular super-refractive' and dutting layers
would oe expected to develop. Inclee.d, records for 1945-19S0, during
which radiosonde upper-air soundings were launched from Washington
National Ail'port, reveal a ml'~h stronger tendcn('y for the fonnation of
Hllomi.ilou5 propagation cOlldJtions than the Silver IliJ] data.
The profiles for 25 ,July and 26 .July, 2200 LST arc lIIore comrletc
than the 19 July profile, altho\1~h some significant levels were noted
as missing from thp 2h July profile. Otherwise, th~' f()1'e~,oiJ1g COIPlllPllts
apply to these prof] les as wl'll. The 2:; .July profi Ie ShU\\~i ;I super-
refractive sllrr:Jc~' In)'cl' and a strong ell,vnted duct; there is a /\.(,01;
(B.~°F) telllpCl'llture inversioll through till' elevated (Iud. It Ls perhaps
:;ignifi.cant that uni,\ent iLiad radar target:'. begall 1Ijl]lcarin~ at 211:10 LST