Earths surface and adjacent air, accomplished
(mainly at night) whenever Earths surface suffers a
net loss of heat due to terrestrial radiation.
RADIATION FOGA major type of fog, produced
over a land area when radiational cooling reduces
the air temperature to or below its dew point.
RAINBOWAny one of a family of circular arcs
consisting of concentric colored bands, arranged
from red on the inside to blue on the outside, which
may be seenonasheet of water drops (rain, fog,
REDUCTIONIn general, the transforma-tion of
data from a raw form to some usable form. In
meteorology, this often refers to the con-version of
the observed value of an element to the value that it
theoretically would have at some selected or
standard level, usually mean sea level. The most
common reduction in observing is that of station
pressure to sea level pressure.
REFLECTIONThe process whereby a surface of
discontinuity turns back a portion of the incident
radiation into the medium through which the
REFLECTIVITYA measure of the fraction of
radiation reflected by a given surface; defined as
the ratio of the radiant energy reflected to the total
that is incident upon that surface. The reflectivity of
a given surface for a specified broad spectral range,
such as the visible spectrum or the solar spectrum,
is referred to as albino.
REFRACTIONThe process in which the direction
of energy propagation is changed as the result of a
change in density within the propagating medium,
or as the energy passes through the interface
representing a density discontinuity between two
RESULTANT WINDIn climatology, the vectorial
average of all wind directions and speeds for a
given level at a given place for a certain period, as a
month. It is obtained by resolving each wind
observation into components from north and east,
summing over the given period, obtaining the
averages, and reconverting the average components
into a single vector.
particles suspended in a medium of a different
index of refraction diffuse a portion of the incident
radiation in all directions.
SEA BREEZEA coastal local wind that blows from
sea to land, caused by the temperature difference
when the sea surface is colder than the adjacent
land. Therefore, it usually blows on relatively calm,
sunny, summer days; and alternates with the
oppositely directed, usually weaker, night land
SEA-BREEZE FRONTA sea breeze that forms out
over the water, moves slowly toward the coast and
then moves inland quite suddenly. Often associated
with the passage of this type of sea breeze are
showers, a sharp wind shift from seaward to
landward, and a sudden drop in temperature. The
leading edge of such a sea breeze is sometimes
called the sea breeze front.
SEA LEVELThe height or level of the sea surface.
SEASONA division of the year according to some
astronomical or climatic. Astronomical seasons
extend from an equinox to the next solstice (or vice
versa). Climatic seasons are often based on
precipitation (rainy and dry seasons).
circulation features of synoptic scale.
SECONDARY FRONTA front that forms within a
baroclinic cold air mass that itself is separated from
a warm air mass by a primary frontal system. The
most common type is the secondary cold front.
derivative) of a vector field along a given direction
in space. The most frequent context for this concept
is wind shear.
SHEAR LINEA line or narrow zone across which
there is an abrupt change in the horizontal wind
component parallel to this line; a line of maximum
horizontal wind shear.
SHORT-WAVE RADIATIONA term used loosely
spectrum (roughly 0.4 to 1.0 micron in wavelength)
from long-wave radiation.
SIBERIAN HIGHA cold-core high--pressure area
that forms over Siberia in winter, and which is
particularly apparent on mean charts of sea-level
SINGULAR POINTIn a flow field, a point at which
the direction of flow is not uniquely determined,
hence a point of zero speed, e.g., a col.