SMOOTHINGAn averaging of data in space or
time, designed to compensate for random errors or
fluctuations of a scale smaller than that presumed
significant to the problem at hand; the analysis of a
sea-level weather map smoothes the pressure field
on a space-scale more or less systematically
determined by the analyst by taking each pressure
as representative not of a point but of an area about
SOLAR CONSTANTThe rate at which solar
radiation is received outside Earths at-mosphere
on a surface normal to the incident radiation, and at
Earths mean distance from the Sun.
SOLSTICE(1) Either of two points on the Suns
apparent annual path where it is displaced farthest,
north or south, from Earths equator. The Tropic of
Cancer (north) and Tropic of Capricorn (south) are
defined as the parallels of latitude that lie directly
beneath a solstice. (2) Popularly, the time at which
the Sun is farthest north or south; the time of the
solstice. In the Northern Hemisphere, the summer
solstice falls on or about 21 June, and the winter
solstice on or about 22 December. The reverse is
true in the southern latitudes.
SPECIFIC HEATThe heat capacity of a system per
unit mass. That is, the ratio of the heat absorbed (or
released) by unit mass of the system to the
corresponding temperature rise (or fall).
SPECIFIC HUMIDITYIn moist air, the ratio of the
mass of water vapor to the total mass of the system.
For many purposes it may be approximated by the
SQUALL LINEAny non-frontal line or narrow
band of active thunderstorms.
vertical distribution of atmospheric temperature,
pressure, and density which, by international
agreement, is taken to be representative of the
atmosphere for purposes of pressure altimeter
calibrations, aircraft performance calculations,
aircraft and missile design, ballistic tables, etc. The
air is assumed to obey the perfect gas law and the
hydrostatic equation, which, taken together, relate
temperature, pressure, and density variations in the
vertical. It is further assumed that the air contains
no water vapor and that the acceleration of gravity
does not change with height.
STRATOSPHEREThe atmospheric shell above the
troposphere and below the mesosphere. It extends,
therefore, from the tropopause to the height where
the temperature begins to increase in the 20- to
SUBLIMATIONThe transition of a substance from
the solid phase directly to the vapor phase, or vice
versa, without passing through an intermediate
SUBSIDENCEA descending motion of air in the
atmosphere, usually with the implication that the
condition extends over a rather broad area.
inversion produced by the adiabatic warming of a
layer of subsiding air. Vertical mixing of the air
layer below the inversion enhances this inversion.
SUBTROPICAL HIGHOne of the semi-permanent
highs of the subtropical high-pressure belt. They
appear as centers of action on mean charts of
surface pressure. They lie over oceans and are best
developed in summer.
SUBTROPICAL HIGH-PRESSURE BELTOne
of the two belts of high atmospheric pressure that
are centered, in the mean, near 30°N and 30°S
SUNSPOTA relatively dark area on the surface of
the Sun, consisting of a dark central umbra
surrounded by a penumbra, which is intermediate
temperature decreases with height.
SUPERCOOLINGThe reduction of temperature of
any liquid below the melting point of that
substances solid phase, that is, cooling beyond its
nominal freezing point.
SUPERIOR AIRAn exceptionally dry mass of air
formed by subsidence and usually found aloft but
extreme subsidence processes.
SUPERIOR MIRAGEA spurious image of an
object formed above its true position by abnormal
refractive conditions; opposite of inferior mirage.