CONDENSATION—The physical process by which a
vapor becomes a liquid or solid.
CONDITIONAL INSTABILITY—The state of a
column of air in the atmosphere when its
temperature lapse rate is less than the dry adiabatic
lapse rate but greater than the saturation adiabatic
lapse rate.
CONVECTION—Atmospheric
motions
that
are
predominantly vertical, resulting in the vertical
transport and mixing of atmospheric properties.
CORONA—(1) A set of one or more prismatically
colored
rings
of
small
radii,
concentrically
surrounding the disk of the Sun, Moon, or other
luminary when veiled by a thin cloud. A corona
maybe distinguished from the relatively common
22° halo by its color sequence, which is from blue
inside to red outside, the reverse of that of the 22°
halo. Diffraction and reflection of light from water
droplets produce coronas. (2) The pearly outer
envelope of the Sun.
COUNTERRADIATION—(also
called
back
radiation) The downward flow of atmospheric
radiation passing through a given level surface,
usually taken as Earth’s surface. It is the principal
factor in the GREENHOUSE EFFECT.
CUT-OFF HIGH—A warm high displaced and lying
poleward of the basic westerly current.
CUT-OFF LOW—A cold low displaced and lying
equatorward of the basic westerly current.
CYCLOGENESIS—Any
development
or
strengthening
of
cyclonic
circulation
in
the
atmosphere.
The initial appearance of a low or
trough, as well as the intensification of an existing
cyclonic flow.
CYCLOLYSIS—Any
weakening
of
cyclonic
circulation in the atmosphere.
CYCLONIC—A counterclockwise rotation in the
Northern Hemisphere and a clockwise rotation in
the Southern Hemisphere.
DISPERSION—The process in which radiation is
separated into its component wavelengths.
It
results when an optical process, such as diffraction,
refraction, or scattering, varies according to
wavelength. All of the coloration displayed by
atmospheric optical phenomena are the result of
dispersion.
DOLDRUMS—A nautical term for the equatorial
trough, with special reference to the light and
variable nature of the winds.
DOWNWIND—The direction toward which the wind
is blowing; with the wind.
DRY AIR—In atmospheric thermodynamics and
chemistry, air that contains no water vapor.
ELECTROMAGNETIC WAVES—Disturbances in
electric and magnetic fields in space or in material
media,
resulting
in
the
propagation
of
electromagnetic energy (radiation).
EQUINOX—(1)
Either
of
the
two
points
of
intersection of the Sun’s apparent annual path and
the plane of Earth’s equator. (2) Popularly, the time
at which the Sun passes directly above the equator;
the “time of the equinox.” In the Northern
Hemisphere, the vernal equinox falls on or about 21
March, and the autumnal equinox on or about 22
September. These dates are reversed in the
Southern Hemisphere.
EVAPORATION—The physical process by which a
liquid or solid is transformed to the gaseous state.
FRONT—The interface or transition zone between
two
air
masses
of
different
density.
Since
temperature distribution is the most important
regulator of atmospheric density, a front almost
invariably
separates
air
masses
of
different
temperature.
FRONTAL INVERSION—A temperature inversion
in the atmosphere, encountered upon vertical
ascent through a sloping front.
FRONTAL SURFACE—Refers specifically to the
warmer side of the frontal zone.
FRONTAL SYSTEM—Simply, a system of fronts as
they appear on a synoptic chart. This is used for (a)
a continuous front and its characteristics along its
entire extent, including its warm, cold, stationary,
and occluded sectors, its variations of intensity, and
any frontal cyclones along it; and (b) the
orientation and nature of the fronts within the
circulation of a frontal cyclone.
FRONTAL ZONE—The transition zone between two
adjacent air masses of different densities bounded
by a frontal surface.
FRONTOGENESIS—The initial formation of a front
or frontal zone.
AI-2
