~HY have been associated witl. local intensification of the dueting
layer. The nature of the visual objects is nct as clear, although
at least two of them appear to have been superior mirages of ships
beyond the normal horizon. There were TJossibly some meteor sightings
involved.
The meteorological conditions were quite Llteresting. The warm,
dry air was apparently quite close to the w~tel surface. at least in
piaces. Dat·\ from Vandenberg and San Nicholas i~~land indicate that in
places the inversion ",a~ no thick€'r tha.n about 90 m. on mb pressure
differ~nce). The c.;ntrast that may have existed can he calculated
from these data:
At or Ncar Sea Surface: At ~)() ~1eters OT' Les'>:
Pres~ure:
Temperature: of·:
°C:
<'K:
o
Optical N (S570A)
1()O ,l mb
58°F
14°C
287°K
27:: (ppm)
~i94 mb
90"r:
,~2"C
!iOS"K
256 (:)pm)
111f1 optical refractive inJex /;radicnt that lIIay have existed at
the time '... as therefore on the order of -210 ppm. km- 1 , or a somewhat
greater negative value. depending upon the thickness c)losen for the
layer. 'I1H~ value above is computell as (256 .. 275) /(1.090, ba~,cu on the
90 m. nlu;dmum thickness assumed. Sinel' the l"rltical value of the
gradient for a superior mirage is -157 pplil. km-I. it is quite apparent
that the l'onditions requireJ for the formation of cxtcndcu supet'ior
mirages \o!erc most llkl"}y present all the datI"' ill question.
'111E' onl)' problem with thLs explanation is the reported C'levHtior, anglcc
of 1(1". b\it as po i ntcll Ollt in the conclusions to th is ch:lpter stich
l'stirnatcs by visual observers arc invariably ovcr-estimated by a latHe
factor.
~Hy have been associated witl. local intensification of the ducting
layer. The nature of the visual objects is net as clear, although
at least two of them appear to have been superior mirages of ships
beyond the nomal horizon. l'here were TJossibly some meteor sightings
:involved.
The meteorological conditions were qlJ.ite i .. lteresting. The warn,
dry air was apparently quite close to the w~teI surface, at least in
piaces. [Jat~\ from Vandenberg and San Ni~holas island indicate that in
pl aCe~; the inversion ~;as no thi ckf:'r than about ';lO m. (H) mb pressure
..Ii ffer~n(;"'). TIlt' (;,lntrast that may have existed (;Bn be calculated
from these Jata:
:'t or Near Sea Surface: At !) () ~leters OT Les,,:
_._------- ----~-.~-.-
Pres~ul'E': 1()O4 mil ~i94 mb
TempcratuTu: of· : 58°r: ~1() 0 F
°C: 14°C ,~2°C
OK: 287°K :;OSoK
0
Optical N (S:'70A) 27':' (ppm) 256 (;lpm)
111P, optical refractive inJex l~radient that Illay havn f~xisted at
-1
the time was therefore on the order of -210 ppm. km , or a somewhat
greater ncgativ'.! value, depending upon the thickness ChOSt'1l for the
layer. '11w value above is computet! as (256 .. 275) IO.OrlO, ba~,('d on the
90 1TI. nlu.dmum thickness assuilled. SineI' tht~ crItical value of the
-I
gradient for a superior mirage is -157 pplll. km it is quito appilI'cnt
that the "onditions required for the fOrl1llltioll of extended supcl'ior
mirages \<.'I'1'E' most llk!.'1y pre:-;ellt Oil the dat ... in quc~tion.
'(111:' onl)' l'rLlhtern with this explanation is the 1'C'jlortcd dCVHtior. (Ingle
of 10°, bnt as pointed out in the conc.1usions to thi s ch;lpter sll<.:h
t'stimatcs hy vi:;ual nb~cl'vcrs are invariahly over-estilllated hy a 11lJ'l\l'
factor.