Transcript A1 : Monson (lesson)

Seasonal reversal of wind
direction
hot air rises
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hot air
expands
.
.
heated
ground surface
. . . .cold
. . .air. .sinks
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.. ....... ......
.. ....... .....
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. . . . .cold
. . .air. . . . . .
contracts
cooled
ground surface
Low pressure near the ground
High pressure near the ground
When air is heated,
When air is cooled,
air expands and rises.
air contracts and
sinks.
As the air near the ground
becomes less dense / lighter ,
the air pressure becomes lower.
As the air near the ground
becomes denser / heavier ,
the air pressure becomes higher.
Low pressure
High pressure
30°N
Cooler air contracts
and sinks
High pressure
0°
Hot air expands
and rises
30°S
Cooler air contracts
and sinks
1. Pressure
gradient force
Wind blows from high pressure areas to low pressure areas.
2. Coriolis
force (created by the rotation of earth)
Winds are deflected to the right in the northern hemisphere
and to the left in the southern hemisphere.
The word monsoon is derived from the Arabic word for “a season”.
It refers to the seasonal reversal of wind direction.
Its results from the different rate of heating and cooling between land and sea, and the pressure
difference between large land masses in northern and southern hemisphere in various seasons.
Land heats up and cools down more quickly
than the land.
summer:land is hotter: lower pressure over land
sea is cooler : higher pressure over sea
wind blows from sea to land as onshore wind
winter :land is cooler : higher pressure over land
sea is warmer : lower pressure over sea
wind blows from land to sea as offshore wind
Earth’s Revolution
21 Mar
In winter solstice,
overhead sun lies on
0°
Tropic of Capricorn
22 June
23½°N
In summer solstice,
overhead sun lies on
Tropic of Cancer
23½°S
22 Dec
0°
In vernal & autumnal
equinoxes, overhead
sun lies on the
equator
23 Sept
June
L
onshore SE monsoon
23½°N
warm, moist (Tm)
onshore SW monsoon
H
offshore SE monsoon
cold, dry (Pc)
In June, the overhead sun lies on Tropic of Cancer (23½°N).
It is winter in Australia. High pressure develops over Australia.
Yet, it is summer in China. The land is intensely heated. So, low
pressure develops over the Mainland.
Since winds blow from high pressure areas to low pressure
areas, wind blows from Australia to the mainland China.
According to Coriolis force, winds are deflected to the left in
the S. hemisphere. So, in N. Australia, winds blow offshore in a
northwesterly direction. After crossing the equator, winds are
deflected to the right in the N. hemisphere. They blow onshore
as SW monsoon in India.
On the Asian continent, since South China Sea heats up slowly,
pressure is relatively higher than that of the Mainland. So,
winds blow onshore from the sea to Hong Kong and S. China as
onshore SE monsoon.
December
H
NW monsoon
NE monsoon
cold, dry (Pc)
NW monsoon
L
warm, moist (Tm)
23½°S
In December, the overhead sun lies on Tropic of Capricorn (23½°S).
It is winter in China. The land is intensely cooled. High pressure
develops over China. Yet, it is summer in Australia. So, low pressure
develops over Australia.
Since winds blow from high pressure areas to low pressure areas,
wind blows from China to Australia.
According to Coriolis force, winds are deflected to the right in
the N. hemisphere. So, in S. China, winds blow offshore in a
northwesterly direction. In India, winds blow offshore in a
northeasterly direction.
After crossing the equator, winds are deflected to the left
in the S. hemisphere. They blow onshore as NW monsoon in
Australia.
2002#1
Describe how air massses affect the climate in
monsoon Asia. In terms of atmospheric circulation,
explain the different climatic characteristics of the
Inter-tropical Convergence Zone and the Polar Front
in the western Pacific region.
I. Introduction
II. Content
A. Climate of monsoon Asia
9
B. Comparison of climatic conditions in tropical regions
& temperate regions in relation to wind
III.Conclusion
18
I. Introduction
1. delimit monsoon Asia
2. def. monsoon
II. Content
A.
How air masses  climate of monsoon Asia
Tm
Indian Ocean or Pacific Ocean
hot + wet
Pc
N. Asia
Cold + dry
2001#2
Geographers commonly use the term “monsoon Asia”
refers to a region in Asia with seasonal shifts of
wind patterns.
Describe the spatial extent of the monsoon over the
Asian continent and explain how they are formed.
Discuss the impacts of monsoons on the weather and
farming activities in South China.
Essay outline : 2001 #2