Environmental Engineering Reference
In-Depth Information
Depression
(The) A period of major economic decline
in the 1930s associated with reduced industrial
activity, high unemployment and the collapse of
international trade.
desert
An area of permanent
aridity,
characterized by
sparse,
xerophytic vegetation,
or, in some areas,
by the complete absence of plant life. Almost 30
per cent of the earth's surface exhibits desert
characteristics of some form. The world's largest
desert is the Sahara, occupying some 8.5 million
sq km in North Africa.
desertification
The expansion of
desert
or desert-like
conditions into adjacent areas. May be initiated
by natural environmental change, by human
degradation of marginal environments or a
combination of both.
Desertification Convention
A proposal presented at
UNCED
aimed at addressing the problems of those
areas suffering from desertification.
diatoms
Microscopic, unicellular aquatic organisms.
dimethyl sulphide (DMS)
A sulphur compound
emitted by phytoplankton during their seasonal
bloom. It is oxidized into
sulphur dioxide
and
methane sulphonic acid (MSA)
.
drought
(A period of) reduced water availability
occurring when precipitation falls below normal,
or when near normal rainfall is made less effective
by other weather conditions such as high
temperature, low humidity and strong winds.
drought prediction
The attempt to forecast the
occurrence of drought so that responses can be
planned and consequences much reduced.
dry deposition
A form of
acid precipitation
consisting
of dry acidic particles. The particles are converted
into acids when dissolved in surface water at which
time their environmental impact is similar to that
of
wet deposition
.
dry farming
A technique which involves the
preservation of several years of
precipitation
to be
used for the production of one crop. It includes
the use of deep ploughing, to provide a reservoir
for the rain that falls, plus a combination of
techniques to reduce losses by
evapotranspiration
.
dry sedimentation
The fallout of dry particulate matter
from the atmosphere under the effects of gravity.
Dustbowl
(The) An area of the
Great Plains,
stretching
from Texas in the south to the Canadian Prairies
in the north, which suffered the effects of
desertification
in the 1930s. A combination of
drought
and inappropriate farming practices
caused the destruction of the
topsoil
and allowed
it to be carried away by the wind.
Dust Veil Index (DVI)
A rating system developed by
climatologist H.H.Lamb to provide an assessment
of the impact of volcanic eruptions on
atmospheric
turbidity
and hence on global
weather
and
climate
.
dynamic equilibrium
see
environmental equilibrium
.
E
earth/atmosphere system
see
system
.
Earth Summit
Popular name for the
United Nations
Conference on Environment and Development
(UNCED)
.
easterly tropical
jet A rapidly moving easterly airstream
encountered in the upper atmosphere in
equatorial
latitudes. It is less persistent than
jet streams
in higher latitudes.
ecosystem
A community of plants and animals
interacting with each other and their
environment
.
El Niño
A flow of abnormally warm water across the
eastern Pacific Ocean towards the coast of Peru. It
is associated with changing pressure patterns and
a reversal of airflow in the equatorial Pacific, a
phenomenon referred to as the
Southern
Oscillation
.
electromagnetic spectrum
The arrangement of
electromagnetic radiation as a continuum according
to wavelength. It extends from high-energy
shortwave radiation
such as
cosmic rays
to the
much longer low-energy radio and electric power
waves.
energy budget
The relationship between the amount
of solar energy entering the earth/atmosphere
system and the amount of terrestrial energy leaving.
In theory, these energy fluxes should balance; in
practice it applies only in general terms to the earth
as a whole, over an extended time period. It is not
applicable to any specific area over a short period
of time.
ENSO
An acronym for
El Niño—Southern
Oscillation
.
environment
A combination of the various physical
and biological elements that affect the life of an
organism. Environments vary in scale from
microscopic to global and may be subdivided
according to their attributes. The aquatic
environment for example, is that of rivers, lakes
and oceans, the terrestrial environment that of the
