Kincheloe AFB, Sault Saint ~1arie, t-lich., 1..1-12 September
19L', 2200-2330 LST. Weather: clear, ceillng unlimited, visibility
unlimited (over 20 mi.), no thundersto:t:'1lls in arl~.3, wi nd at surface
140°/4 knots, aloft 240°-270°/15-35 knots. lbe radio refractivity
profile from Sault Saint Marie for the most applicable time is shown
in Fig. 21.
'nlis is a gooCi example of moving raUaT targets that cannot be
seen visually, where there is a "forbidden cone" over the radar 5i te.
Some of the returns were even seen to approach within 5-15 mi. of
the radar and disappear, appaTently subsequently reappearing on the
other side of the radar scope at about the same range that they
disappeared. This sort of behavior is symptomatic of I\P-echocs.
The meteorological data tenti to confirm this interpretation.
TIle refractivity profile shown in Fig. 21 displays three pecu}jaritics:
a strong subrefractive layer at the surface, a strong elevated duct
at 325-520 m. (about 1100-1700 ft.) and a super-refractive layer at
1070-1360 m. (about 3,500-4,500 ft.). A ray-tracing is shown for this
profile in Fig. 20. 'Mle ray shows noticeable charq~cs in curvature
as it passes through the different iayers, an indication that strong
partial reflections would be expected. Wi~h this profi Ie, movi ,g
AP-echoes, produced in the manner described by Rorden and Vickers
(1953), could be expected to appear at apparent heights of between
2,000-3.000 ft. and 7,000-9,000 ft. No height infoTIlation was sup-
plied with this report, so the calculation ahove cannot he verified.
In summary, it appears that this is a case of observations of
moving AP-cchoes produced by unusually well 5tratificd atmospheric
conditions.
lS6-~ Gulf of Mcxi co, l;oa~t Guard Cutter "Sebago," 25"47' N
89°24'W, S November 1957, llSlO-1537 1,:3'1'. Weather: not given, but
~.pparently 50me clouds in area. The most applicable T8dio refractivity
247
Kincheloe AFB, Sault Saint Harie, Mich., 1..1-12 September
19G', 2200-2330 LST. Weather: clear, ceilIng unlimited, visibility
unl Imi ted (over :.:0 mi.), no thunders tonns i n aI'f~~, wi nel at surface
140°/4 knots, aloft 240°_270°/15_35 knots. "111e radio refractivity
profile from Sault Saint Marie for the most appJicable time is shown
in Fig. 21.
"nl i sis a gOOG exampl e of rnoV' j Ilg ruoar targets that cannot be
seen visually, where there is a "forbidden cone" over the radar site.
Some of the returns were even seen to approach within 5-1S mi. of
the radar and disappear, apparently subsequently reappearing on the
other side of the radar scope at ahout the same range that they
disappeared. This sort of behavior is symptomatic of AP-echoes.
The meteorological data tend to conn rm this interpretation.
T]1e refractivity profile shown in Fig. 21 displays three pecuharities:
a strong subrefractlvc layer at the surface, a strong elevated duct
at 325-520 m. (about 1100-1700 ft.) and a super-refractive layer at
1070-1360 m. (about 3,500-4,500 ft.). A ray-tracing js shown for this
profile in Fig. 20. 'Dle ray shows noticeable changes in cllrvatun~
as it passes through the different :ayers, an indication that strong
partial reflections would be expected. Wi"!:h this profi Ie, movi ,g
AP-echoes, produced in the manner described by Borden and Vickers
(1953), could be expected to appear at apparent heights of between
2,000-3,000 ft. and 7,000-9,000 ft. No height informatjon wa~ sup-
plied with this report, so the calculation ahove cannot be verified.
In summary, it appears that this is it case of observations of
movillg AP-echoes produced by unusually ",ell "trati fi cd atmospheriC
conditions.
156-.12.:.. Gulf of Mexico, Coa~t Guard Cutter "Sebago," 25"47'N
R9°24 I W, S November 1957, ilS!O-i537 LST. Weather: not given, but
apparently some clouds in aroa. The JIlost applicable radio refractivity
247