SUPERSATURATIONThe condition existing in a
given portion of the atmosphere (or other space)
when the relative humidity is greater than 100
percent, that is, when it contains more water vapor
than is needed to produce saturation with respect to
a plane surface of pure water or pure ice.
SURFACE BOUNDARY LAYERThat thin layer of
air adjacent to Earths surface, extending up to the
so-called anemometer level (the height above the
ground at which an anemometer is exposed;
usually 10 meters to 100 meters).
SURFACE CHART(also called surface map,
sea-level chart, sea-level pressure chart) An
observations. It shows the distribution of sea level
pressure (positions of highs, lows, ridges, and
troughs) and the location and nature of fronts and
air masses. Often added to this are symbols of
occurring weather phenomena, analysis of pressure
tendency (isallobars), indications of the movement
of pressure systems and fronts, and perhaps others,
depending on the use of the chart.
SURFACE INVERSIONA temperature in-version
based at Earths surface; that is, an in-crease of
temperature with height beginning at ground level.
SURFACE OF DISCONTINUITYA
separating two fluids across which there is a
discontinuity of some fluid property, such as
density, velocity, etc., or of some derivative of one
of these properties in a direction normal to the
interface. An atmospheric front is represented
ideally by a surface of discontinuity of velocity,
density, temperature, and pressure gradient; the
tropopause is represented ideally by a surface of
discontinuity of, for example, the derivatives: lapse
rate and wind shear.
SYNOPTICIn general, pertaining to or affording an
overall view. In meteorology, this term has become
somewhat specialized in referring to the use of
meteorological data obtained simultaneously over
a wide area for the purpose of presenting a
comprehensive and nearly instantaneous picture of
the state of the atmosphere.
SYNOPTIC CHARTIn meteorology, any chart or
map on which data and analyses are presented that
describe the state of the atmosphere over a large
area at a given moment in time.
SYNOPTIC SCALEThe scale of the migratory
high- and low-pressure systems (or cyclonic
waves) of the lower troposphere, with wavelengths
of 1,000 to 2,500 km.
SYNOPTIC SITUATIONThe general state of the
atmosphere as described by the major features of
TEMPERATURE INVERSIONA layer in which
temperature increases with altitude.
TERTIARY CIRCULATIONThe generally small,
localized atmospheric circulations.
represented by such phenomena as the local winds,
thunderstorms, and tornadoes.
THERMAL(1) Pertaining to temperature or heat.
(2) A relatively-small-scale rising current of air
produced when the atmosphere is heated enough
locally by Earths surface to produce absolute
instability in its lower layers. The use of this term is
usually reserved to denote those currents either too
small and/or too dry to produce convective clouds;
thus, thermals are a common source of low-level
THERMAL GRADIENTThe rate of variation of
temperature either horizontally or vertically.
THERMAL HIGHAn area of high pressure
resulting from the cooling of air by a cold
stationary over the cold surface.
THERMAL LOWAn area of low atmospheric
pressure resulting from high temperatures caused
by intense surface heating. They are stationary with
a generally weak and diffuse cyclonic circulation.
They are non-frontal.
extending from the top of the mesosphere to outer
space. It is a region of more or less steadily
increasing temperature with height, starting at 70
or 80 km.
TORNADOA violently rotating column of air,
pendant from a cumulonimbus cloud, and nearly
always observable as a funnel cloud or tuba.
TRIPLE POINTTerm commonly used to denote the
apex of an occlusion.
TROPICAL AIRA type of air whose characteristics
are developed over low latitudes. Maritime tropical
air (mT) is produced over the tropical and
subtropical seas, while continental tropical air is
produced over subtropical arid regions.