Page 10 - The World About Us

Rainforest
1.1.1
2.1.3

What shapes the distribution of tropical rainforests?

Tropical rainforest is associated
with the climate found in the
Equatorial regions (see fig.229, p87)
which are found in a rela vely narrow
belt north and south of the Equator.
Tropic of
The climate here is dominated by Cancer Central
the Inter-Tropical Convergence Zone America
(ITCZ) and low pressure. The ITCZ is Manaus South East
Asia
where the air, returning from the Sub- Equator Medan
Tropical High Pressure (STHP) as the Congo
Trade Winds, meets and is forced Amazonia Basin Australasia
upwards. This upli is assisted by the Tropic of
intense hea ng of the ground by the Capricorn Madagascar
overhead Sun. The warm ground heats
the air above it which then expands
and rises. This rising air then begins to Tropical and monsoon rainforest
cool.
fig.20 The distribution of tropical rainforests (other major biomes are in outline).
The heat from the overhead Sun
increases evapora on from the The high levels of sunlight and
surfaces of the land and plants. This abundance of water are perfect
evaporated water is added to by water condi ons for the growth of trees.
vapour transpired by plants as a bi- These trees release vast quan es of
product of photosynthesis. water from their leaves when they
As the moisture-saturated air rises, photosynthesize. This water returns as
it cools and the water vapour begins to rain, much of it to be recycled once
condense. The rapid upli from the again by the trees.
warm ground, coupled with latent heat Trees are important in the water
released as the water condenses, helps and nutrient cycles within the forest
to create towering cumulonimbus ecosystem. Once these trees are cut
thunderclouds. In turn, these clouds down, the soils can quickly become
deliver torren al downpours. impoverished and the climate of the
A ernoon rainfall will cool the region may change, with rainfall totals
ground surface, reducing the significantly reduced.
atmospheric upli un l the next day fig.21 Costa Rica cloudforest.
when the Sun once again rises high in
fig.23 The weather of a typical Equatorial day.
the sky and heats the Earth's surface.
4. Rising air cools and water 5. Intense upli develops
fig.22 The climate of Manaus. condenses to form clouds towering cumulonimbus
thunder clouds.
2. As the Sun rises in
350 35
the sky it heats the
ground and trees. 6. Intense rainfall 7. Clouds break
300
Mean monthly rainfall (mm) 200 20 Mean monthly temperature ( 3. Warm surfaces heat descends on forest,
30
up as it rains.
25
250
the air which expands
cooling surfaces and
and begins to rise, taking
reducing further upli .
water vapour with it.
150
15
100
50 10 o
5 C)
0 0
J F M A M J J A S O N D 1. Sun rises in the morning 8. Sun sets in clear sky, humid air traps heat overnight.
10

There are major tropical rainforests in the world.