Environmental Engineering Reference
In-Depth Information
soil texture
A measure of the proportions of sand, silt
and clay in a soil.
solar radiation
Radiant energy given off by the sun.
Since the sun is a very hot body, the bulk of the
radiation is high energy at
ultraviolet
and
visible
light
wavelengths.
soot
Finely divided particles of carbon formed during
combustion, which readily combine with each other
into clusters or strings, and are effective at
absorbing radiation across the entire spectrum.
Southern Oscillation
The periodic reversal of pressure
patterns and wind directions in the atmosphere
above the equatorial Pacific Ocean. Part of the
Walker Circulation
and responsible for the
development of
El Niño
. (See also
ENSO
.)
spatial resolution
An indication of the detail available
from weather and climate models, determined by
the horizontal and vertical distribution of the grid
points for which data are available, and at which
the appropriate equations are solved.
spectral models
Atmospheric circulation models which
focus on the representation of atmospheric
disturbances or waves by a finite number of
mathematical functions. The progressive solution
of a series of equations allows the development of
the atmospheric disturbances to be predicted.
sphagnum
A type of moss which is a common
component of the plant community in temperate
peat bogs. Being acid tolerant it colonizes the
margins of acid lakes.
spring flush
The rapid run-off of water from melting
snow and ice, common in mid to high latitudes at
the end of winter, which carries the winter's
accumulation of acidity into rivers and lakes in a
matter of days, rapidly reducing the
pH
of these
waterbodies.
Statement of Forest Principles
A general statement
from the
Earth Summit
which acknowledges the
need to balance exploitation and conservation of
forests, but with no provision for international
monitoring or supervision.
steady state system
A
system
in which inputs and
outputs are equal and constant, and in which the
various elements are in equilibrium. Any change
alters the relationships among the components of
the system, creating imbalance, and setting in train
a series of reponses which attempt to restore
balance.
steppe
A semi-arid area characterized by short-grass
vegetation. Considered transitional between desert
and sub-humid climates. In areas closer to the latter,
steppe may include woody shrubs.
stratopause
The boundary between the
stratosphere
and
mesosphere,
located at about 50 km above the
earth's surface.
stratosphere
The layer of the atmosphere lying above
the
tropopause
. It is characterized by an
isothermal layer (temperatures remain constant)
up to about 20 km above the earth's surface,
beyond which temperatures rise again from
about-50°C to reach close to 0°C at the
stratopause
. This is the result of the presence of
ozone which absorbs incoming
ultraviolet
radiation,
causing temperatures to rise.
stratospheric ozone
See
ozone
.
strip-cropping
The practice of cultivating land in long
narrow strips of different crops, to ensure that the
land always retains some vegetation cover, and is
therefore protected from
soil erosion
.
Study of Critical Environmental Problems
(SCEP)
Produced in 1970, this was the first major study
to draw attention to the global extent of human-
induced environmental issues.
Study of Man's Impact on Climate (SMIC)
A 1971
report which grew out of issues raised originally in
the
SCEP
. It focused on inadvertent climate
modification.
subsidence
The sinking of air in the atmosphere.
Subsidence may be associated with the cooling
of air close to the surface—as in cold
an
ticyclones
—or with the larger scale
circulation—in the descending arm of a
convection cell, for example.
subsistence farming
The production of sufficient food
and other necessities to meet the requirements of a
farm unit, leaving no surplus for sale and little for
storage.
sulphate (particle)
A negatively charged
ion
containing
one
atom
of sulphur and four of
oxygen
.
sulphur
A non-metallic element present in all living
matter. Its release as
sulphur dioxide
during the
combustion of
fossil fuels
is a precursor of
acid
rain
.
sulphur dioxide
An acid gas in which each
molecule
contains one
atom
of sulphur and two of
oxygen
.
It is a product of the combustion of materials
containing sulphur.
sunspots
Dark spots that appear on the surface of the
sun, associated with strong electromagnetic activity.
