O-Level ZIMSEC Geography : Air Masses And Pressure Belts
Hello Geography students
This is Sir
Ndhlovu, your favourite Geography teacher at E.Blue Institute.
Our aim at
E.Blue Institute is helping you pass not only Geography but all five O-levels
so that you can be able to proceed towards A-Level, a polytechnic or any
institution of higher learning. We are a high school collage located
in Budiriro 5, Harare.
To help you
pass we apply many creative teaching technics. One of the best technics is
called goal setting and motivation. Goal setting and motivation is all about
letting students know that in order to live a great life in the future as a
high income professional (earning +$10 000.00 per month) i.e a lawyer, medical
doctor, engineer a student should first and foremost pass his or her O-levels
today.
A student
motivated by specific, measurable and realistic goals is in a better position
to pass O-levels than one who doesn’t have goals at all.
Now what are
key terms a student must know in as far as Air Masses and Pressure Belts are concerned.
The topic of Air Masses and Pressure Belts is a very important one because
understanding it makes it easy to in turn understand climate and weather.
I have therefore,
created these summary notes whose aim is to enhance the understanding of air
masses by presenting an overview or framework of the topic. This overview helps
students find a starting point in their learning journey focusing on air masses
and indeed the entire topic of Weather and Climate.
1.Key terms
1.1 Convergence zone : This is a low pressure area where
similar or different air masses meet. On a global scale there are only three
such places namely the Equatorial low
pressure belt within the tropics and the two Sub-Polar low pressure belts in the mid-latitudes (temperate
areas) of both hemispheres.
1.2 Divergence zone : This is a high pressure area from
which air masses move away. On a global scale there are four such areas as follows;
(a) The Sub-Tropical high pressure belt located just under or beneath the Tropic of Cancer in the mid-latitudes of
the northern hemisphere.
(b) The Sub-Tropical high pressure belt just
under or beneath the Tropic of Capricorn in
the mid-latitudes of the southern hemisphere.
(c) The two Polar high pressure belts located
within the polar areas of both hemispheres.
1.3 Air mass : This is a large body of air that
has temperature and humidity characteristics
that are horizontally uniform.
2. Key concept
When air
masses move they are called winds and such movement is controlled by the
principle that winds always move from a place of high pressure to a place of low
pressure. This is illustrated in
figure 1 and in the video above.
Figure 1
3. Air masses
affecting Zimbabwe
3.1 The Equatorial low
pressure belt is the same as the Inter-tropical
convergence zone (ITCZ).
3.2 The Inter-tropical convergence zone is a low pressure
area within the tropics where the north-east and south-east trade winds
converge. It is also associated with high temperature and rainfall.
3.3 In a year the ITCZ changes positions twice; In January it
moves to the southern hemisphere bringing high rainfall and high temperatures
to Zimbabwe but in July the ITCZ moves to the northern hemisphere.
3.4 Zimbabwe is affected by four air masses namely; a Tropical continental from the
north-west also known as Congo Air,
a Tropical continental from the
south-west, a Tropical maritime from
the north-east and a Polar maritime from
the south-east.
4.Classification and
naming of Air Masses
4.1 Air masses are classified according to source region. This
means if they are originating over a land mass they are classified as continental (dry) but if its over a
water body they are classified as
maritime (wet) .
4.2 Air masses are named according to source region and
temperature. This means if they are originating in the tropics which are warm they are called Tropical (continental or maritime) but
if they are from the Polar regions which are cold they are called Polar (continental
or maritime) .
THE END
P.S To learn more students are welcome to ask
specific questions in the COMMENT SECTION below.
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