06-May-2002 --
On April 29th, when inbound to the Baltic Sea, we had visited 55°N 11°E, this time, outbound, we can submit 56°N11°E,
an offshore point very close to the so called "T-Route", a buoyed
transit
route from the North Sea to the Baltic Sea through the
Danish Islands.
About three hours prior our arrival at the confluence, coming from the
South, we had passed below the Østerrenden Bridge
("Bridge over the Eastern
Channel"). The Bridge is part of the connection
between
Sjælland and Fyn Island. The Østerrenden Bridge connects Sjælland with
Sprogø, and the connection of Sprogø with Fyn is called Vesterrenden
Bridge
("Bridge over the Western Channel"). The construction was completed
around1990.
Between the two pillars of the Østerrenden Bridge there is a
narrow buoyed channel. Navigation under the bridge is tricky and
therefore
Captain Peter took the wheel himself for a while.
Approaching the bridge looks strange in the Radar, it
seems to steer the ship against a wall.
The moment when being exactly below the span is always
spectacular and worth another photo.
Sejerø Island is the closest land to the
confluence.
The "capital" of Sejerø is Sejerby.
And from this confluence we saw something very beautiful:
First we did not realize it, then Captain Peter spotted land in a
direction
where no one was supposed to be. It was a mirage.
Checking the radar we found out that this land was the Swedish coast,
about
53 nautical miles (almost 100 km) away!
On the chart we learned it to be coast around the small Swedish village
of
Höganäs reflecting there.
Mirage, or in this particular case - Super-refraction, is a downward
bending
of rays, caused either when humidity decreases with height or when the
temperature lapse rate is less than normal. When temperature increases
with
height (i.e. when an inversion is present), the downward bending of
rays is
particularly enhanced.
Super-refraction increases both the optical and radio horizons, so that
it
is possible to see and to detect objects which are actually beyond the
geometrical horizon.
Super-refraction can be expected either:
-
in high latitudes wherever the sea surface temperature is
exceptionally
low
-
in coastal areas where warm air blows offshore over a cooler sea
-
and occasionally behind a cold front
Objects beyond the geometrical horizon may become visible, so that
lights
may be raised at much greater distances than expected.
In this particular case we see even a superior mirage as well, i.e. an
inverted image above the real object. This is an occasional effect
produced
when the air is appreciably warmer then the sea. Sometimes an erect
image is
seen immediately above and touching the inverted one. The object and its
images in this distance are quite well-defined.
Superior mirage is most often experienced in high latitudes and
wherever the
sea surface temperature is exceptionally low.