| Natural
systems
By
Marjorie Henry, Contributor In
the last lesson, I promised that I would take some time to share with you on aspects
of the new geography syllabus. In reference to it, I have selected a new topic
that comes under natural system, that is, Section II of the syllabus. This relates
to the variations in the climate in the Caribbean as a result of relief. If you
had purchased a copy of the syllabus as I have encouraged you to do, you would
have noticed that the content for this topic states: 'Influence of relief on climate
in the Caribbean' At
the same time, the specific objective states: 'Explain how relief produces variation
in the climate of the Caribbean.' Relief
here, of course, refers to the general undulations and variations of the land.
Relief affects the local climate of the Caribbean islands. The varying heights
of the land can and do affect the elements of climate such as temperature, rainfall
and winds. Let us discuss each of these separately. TEMPERATURE
There
are areas in the Caribbean that are mountainous. Two examples are the Blue Mountains
in Jamaica, which is approximately 2,229 metres high, and Morn Diabtotin in Dominica,
which rises to about 1,419 metres. I am certain that you are familiar with the
saying, - 'The higher you go the cooler it becomes'. In other words, with an increase
of altitude, there is a decrease in temperature. The rate at which temperature
falls with increase in altitude is 0.6*C for every 100 metres above sea level.
It therefore means that the temperatures on the Blue Mountains at a height of
2,229 metres would be 13*C lower than at sea level. In Dominica, it would be approximately
9°C cooler than the other areas. Height
has little effect upon islands that are low-lying. Examples of low-lying Caribbean
islands are The Bahamas (highest point is less than 200 metres), Antigua (402
metres) and Barbados (333 metres). These islands are generally hotter and drier
than the mountainous ones. The effect of altitude upon temperature, then, is significant
in the Caribbean islands that are mountainous. RAINFALL
The
wettest parts of the Caribbean are associated with the highest parts. When rain-bearing
winds blow across a mountainous island, they are forced to rise. Because of this,
the air cools and condensation occurs leading to the formation of clouds. Heavy
rainfall may occur on the top of the mountain and on the side of the mountain
facing the wind called the windward side. After the air has lost its moisture,
it is dry air that goes down on the other side. This side known as the leeward
slope is drier than the windward slope since it receives significantly less rainfall
than the windward slope. This type of rainfall is called relief or orographic.
WINDS
Strong
winds are experienced on the windward slopes of mountains. Wind speeds are much
lower on the leeward side of the mountains. Here
are a few questions to review the topic today. 1.
What aspects of climate does relief affect? 2.
At what rate does temperature reduce with increase in altitude? 3.
Name one mountainous and one low-lying Caribbean island. State the eight of the
highest points. 4.
What name is given to the type of rainfall that results from the relief of the
land? 5.
Describe the formation of this type of rainfall. 6.
On which side of the slope do strong winds occur? The
textbooks that were used for reference are: 1.
The new edition of The Caribbean Environment for CXC Geography - Mark Wilson.
2. Longman
Geography for CSEC - Jeanette Ottley and Marolyn Gentles. 3.
Principles Of Geography For CXC - Norrell A. London and Mike Senior. Do
additional reading from these and other available textbooks. Marjorie
Henry teaches at Glenmuir High School. | 
