Geoscience Reference
In-Depth Information
INTRODUCTION
The previous part was concerned with the general
principles of energy and our approaches to the
study of physical geography. We now move into
an examination of specific features of the environ-
ment so that we get a better understanding of how
each of these subsystems operates. First we will
consider the atmosphere as, arguably, it is the vital
element that relates to most other aspects of
physical geography, then look at the geosphere
and the biosphere in detail. The topic will conclude
with
Part 5
where we emphasise the interactions
between these components for particular environ-
ments such as drylands, humid tropical areas,
and polar regions for example. Inevitably, with all
the concern over environmental change, there will
be a chapter concerned specifically with change
and what the future may hold for the global
environment.
For our atmosphere section, we need to focus,
initially, on the flows of energy and heat within
the Earth system. The sun is the dominant source
of energy for our planet so we start with its flow
to Earth, how this energy is distributed non-uni-
formly across the globe, and what happens to this
energy. It provides the basis for the understand-
ing of the atmospheric circulation. Another key ele-
ment of the atmosphere is moisture. We cannot
live without moisture; it is needed for drinking
water, for growing vegetation and innumerable
other activities. In addition, it serves other vital
roles: as a greenhouse gas; as a means of trans-
ferring energy around the globe in the form of
latent heat; and, of course, there is a vast reser-
voir of moisture in the oceans which also help with
heat transfer. Because of this important role a
whole chapter is devoted to moisture in the atmos-
phere and another to precipitation once it reaches
the ground surface.
Two chapters are concerned with atmospheric
movement, the first looking at its basic principles
and how these produce the nature of our atmos-
pheric circulation. The second is concerned with
the weather forming systems that develop within
particular circulations of the atmosphere. Often
these are more important for day to day weather
events and some of the more dramatic features
of our atmosphere such as tropical storms and
floods. The availability of satellite images now
means that we can have a much better apprecia-
tion of how these storms evolve and what parts
of the planet are affected.
Much of this part is concerned with the large-
scale features of climate but in reality the climate
near the ground, or the micro-climate, has even
greater variety and interest and, at the same time,
is the part of our climate that we experience most
closely. Because of this, a chapter is devoted to
the way in which surface features modify the large-
scale climate. Surface features such as forests,
slopes and urban areas can all produce very dis-
tinctive changes in comparison with the open,
grass-covered sites which form the basis of most
meteorological observations. They are also vital
to help explain some of the geomorphological and
biogeographical processes that will be covered in
This part concludes with a survey of changes
in climate that have been observed in the recent
geological and historical past. The previous
chapters outlined the principles behind our
present climate but we have to accept that it has
never been constant. There is abundant evidence
that climates in the past have been very different
from those of today. At times we appear to have
had ice advances and at other times periods of
comparable or even greater warmth. We need to
know more about these changes in order to have
a better appreciation of what causes our present
climate as well as providing the setting for
geomorphological and biogeographical processes
of the past.
