DICTIONARY OF GEOPHYSICS, ASTROPHYSICS, and ASTRONOMY

super cloud cluster
called supercell storms account for most tornadoes
and damaging hail. Most supercell storms
move continuously toward the right of the environmental
winds. See multicell storm.
super cloud cluster Deep convection in the
Tropics is organized into a hierarchy of spatial
structures. A typical convective cloud is 10 km
in horizontal scale. Such clouds often gather
into a cloud cluster with horizontal dimensions
of 1 to a few 100 km. A super cloud cluster is a
group of such cloud clusters and has a longitudinal
dimension of a few 1000 km. A super cloud
cluster forms in the rising branch of a Madden–
Julian Oscillation and is exclusively found in
the large warm water region from the equatorial
Indian to the western Pacific Ocean.
supercluster A very large, high density cluster
of rich clusters of galaxies that is flattened
or filamentary in shape, with sizes as large as
150 Mpc. Superclusters appear to surround
large voids creating a cellular structure, with
galaxies concentrated in sheets; in higher density
at the intersection of the sheets (edges); and
in very high density superclusters at the intersection
of edges. Superclusters typically contain
several (2 to 15) clusters and are defined
by a number density of galaxies taken to exceed
some threshold, typically a factor 20 above the
average galaxy number density. The mean separation
between superclusters is reported to be
approximately 100 Mpc.
superconducting string See Witten conducting
string.
supercooling The phenomenon in which a
pure material may be cooled below the usual
transition temperature but not undergo a phase
change. For instance, pure water may be cooled
below 0 ◦ C without freezing. The addition of a
freezing center, or of a small ice crystal will immediately
initiate freezing in such a case. One
can also speak of supercooling with respect to
the condensation temperature.
supercritical flow Flow in an open channel
with a Froude number greater than unity. See
Froude number.
© 2001 by CRC Press LLC
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superflare A stellar flare having 100 to 10
million times the energy of the most energetic
Solar flare. Superflares have been observed on
normal solar-like stars. These flares have durations
of a fraction of 1huptoafewdays, radiate
10 33 to 10 38 ergs, and emit light from radio
waves through X-rays. One theory of their origin
is that they arise from the sudden release of
stored magnetic energy. See RS Canum Venaticorum
stars.
supergeostrophic wind Real wind which is
stronger than the geostrophic wind. Along the
axes of low level jets, it is often found that the
wind speed is larger than the geostrophic wind.
Both supergeostrophic wind and subgeostrophic
wind are the non-geostrophic wind fluctuations
caused by inertia gravitational waves. In general,
there will be severe weather, such as heavy
storms over the supergeostrophic wind regions.
supergiant The evolved phase of the life of
a star of more than about 5 solar masses. The
distinction between giants, bright giants, and
supergiants is somewhat arbitrary (see HR diagram),
but, in general, supergiants will be the
biggest (more than 1,000 solar radio), brightest
(more than 10 4 solar luminosities), and the
shortest-lived (less than 10 6 years). Supergiants,
at least those whose initial mass was
more than about 10 solar masses, will end their
lives as supernovae of Type II. They have vigorous
stellar winds that can reduce the initial mass
of the star by a factor of two or more during their
lives.
supergradient wind Real wind which is
stronger than the gradient wind. It is similar
to supergeostrophic wind. When the pressure
gradient force cannot be balanced by the horizontal
Coriolis force and the centrifugal force,
the supergradient wind will appear. Supergradient
winds often can be found in tornado systems.
In general, supergradient winds are not easy to
create and will evolve to normal gradient winds
due to the Coriolis effect. In practice, it is hard
to determine the radius of curvature of wind required
to determine the gradient wind; thus, it is
hard to determine the existence of the supergradient
wind.