SPin09a Linda Tysk The monsoon seasons in India 1
Name: Linda Tysk Class: SPin09a
Date: 26/11 2010
1 Climate . WorldHistoryatYHS.
th of November 2010. https://worldhistoryatyhs.wikispaces.com/Climate
26 nov 2010 1
SPin09a Linda Tysk Index Introduction 3 Background research 4 Analysis 7 Conclusion 9 Bibliography 10 2
2 In India, a Prayer for Rain Despite a Deluge . NYTimes.com. Somini Sengupta: 6
th July 2007
th of November 2010. http://www.nytimes.com/2007/07/06/world/asia/06monsoon.html?_r=1
26 nov 2010 2
SPin09a Linda Tysk Introduction During three weeks, we have been working with the monsoon and the affects of it. The reason why
I write and study about the monsoon is to understand how a monsoon is created, why it is created,
how the monsoon affects people living in the troubled areas and why it is only created on some
locations and time of year.
I am going to use several books and try to compare the information in them, and I am also going to
use Internet to find websites.
The questions I am going to answer in my text will be:
– What are the causes to why the monsoon is created, and how is it created?
– Why is the monsoon only created in some geographical places in the world?
– Why is monsoons only created in some periods of the year?
– In what ways are people affected by the monsoons?
– What affects does the monsoon have on agriculture?
26 nov 2010 3
SPin09a Linda Tysk Background research India is located in southern Asia and is a country with a population of approximately 1 1 000 000
inhabitants, which is about 17% of the total world population. India consists of a sub-continent
reaching out into the Indian Ocean, with the Bay of Bengal on the right side and the Arabian Sea on
the left. India is also a country that is affected by monsoons, which means wind reversals 3
India is located by the equator and is included in the ITCZ, which is Inter-Tropical Convergence
Zone. The ITCZ is an area with low pressure centered on the equator. By the equator, the sun is
strong since the sun is closest to the earth's surface there, and heats up the earth's surface, which
results in warm air that rises because of lowered density and moist that evaporates. At a certain
altitude known as the dew point temperature, the warm air is cooled down and forms clouds, since
the air contains moist and is turned in to water. This rise of air creates a low pressure at that area, or
an area with less atmospheric pressure than the surrounding areas.
Depression (Low pressure/Cyclone): Low pressure is where moist air is forced to rise because of
1) strong heating by the sun, evaporating the moist air making the air rise because of lowered
density 2) northern and southern trade winds meeting by the equator that encourages the warm air to
That creates an area with less atmospheric pressure than the surrounding areas, which also means
that there's only a relative measurement for low pressure because the pressure can vary but still be
low pressure when the surrounding areas have higher pressure.
Because of the Coriolis-effect, which means that because of the earth's rotation – winds from the
equator is forced in a right-bow in the north, and in a left-bow in the south, since they are drawn by
the low-pressure but at the same time is affected by the Coriolis force. And being affected by the
Coriolis, winds blowing from a low pressure system in the north is moving in a anticlockwise
direction, while they on the south hemisphere move in a clockwise direction because of the Coriolis
force making the winds blow in left-bow.
When the northern and southern trade winds meet, they don't have exactly the same temperature,
which means that one of the air-masses is lighter than the other, ending with the cooler air-mass
(front) pushing under the warmer and lighter front creating occlusion. During the occlusion, air has
been forced to rise (the warm air) which creates low pressure/depression.
Areas of low atmospheric pressure is characterized by light winds, to fill the low pressure zone
with air and thereby even the atmospheric pressure-differences 7
But when the warm and moist air has risen, the air is encouraged to travel north and south because
of air convergence between tropics, and sinks when it has cooled down, creating two high pressure
3 Chapman, Simon (1998). Complete geography. Oxford: Oxford Univ. Press
4 I bid 5 I bid 6 Corioliseffekten . SMHI.se. SMHI: 8
th of July 2009
th of November 2010. http://www.smhi.se/kunskapsbanken/meteorologi/corioliseffekten-1.4041
7 Chapman, S (1998)
26 nov 2010 4
SPin09a Linda Tysk zones around the latitudes 30 °S and 30°N 8
. Winds from the high pressure zone is then returned to
the equator as trade winds to fill the created low pressure zone, leading to a convection cycle with
formation of cumulonimbus clouds and heavy convectional rainfall by the equator in the low
pressure zone when the warm air has been cooled down and extreme drought in the high pressure
Anticyclones (High Pressure): High pressure is where the air that has been cooled down eventually sinks back to earth again, and
that creates an area with higher atmospheric pressure than the surrounding areas. When the air
sinks, the temperature of the air-mass is increased, leading to evaporation of the rest of the moist in
the air. The lack of moist in the air, prevents the formation of clouds, resulting in cloudless days
where the sun is able to reach through to the earth's surface and heat it up.
The air in a anticyclone moves in the opposite direction compared to in a depression, meaning
clockwise on the north hemisphere and anticlockwise on the south hemisphere 11
. Leading to jet-
streams between them where air from the low pressure is sucked into the high pressure 12
Monsoon (Wind reversals
Monsoon-rainfalls are seasonal rainfalls, where extreme low and high pressures leads to heavy
rainfall two times a year. Monsoons are most common in south and southeast Asia.
Heating over the Indian ocean, the sub-continent of India and the Himalayas are major causes to the
creation of monsoons.
During the year, the area with the highest solar heating shifts north and south on Earth, since
earth is tilting. That means that when it's summer on the northern hemisphere, the area with
maximum solar heating has moved from the equator to the north hemisphere. In the same way
during winter on the northern hemisphere, the area of maximum solar has moved to the southern
hemisphere, meaning that it's summer there. So two times a year, the area of maximum solar heating
is on the equator, once when earth is circulates around the sun between our winter and summer, and
once between summer and winter. When the area of maximum solar heating is on the northern
hemisphere, it has a 90 ° angle to the sun, and the same when it's on the equator and on the southern
In November, the dry season starts in India. By then, the area of maximum solar heating is
moving towards the southern hemisphere and is placed over the Indian ocean south of India. The
sun heats up the ocean and evaporates water from the sea, causing low atmospheric pressure over
the Indian Ocean with growing clouds. So the convection cycle is also moving, creating high
pressure in India with cloudless days and moderate temperatures with light trade winds blowing
from the north in order to equalize the low pressure that has been created in the Indian ocean.
8 I bid 9 Hästbredderna, passadvindarna och vädret i tropikerna . SMHI.se. SMHI: 10
th of August 2009
th of November 2010. http://www.smhi.se/kunskapsbanken/meteorologi/hastbredderna-passadvindarna-och-
10 Chapman, S (1998)
11 Högtryck . http://www.ne.se/högtryck, Nationalencyklopedin, hämtad 2010-11-23.
12 Lågtryck och högtryck samverkar . SMHI.se. SMHI: 10
th of August 2009
th of November 2010. http://www.smhi.se/kunskapsbanken/meteorologi/lagtryck-och-hogtryck-samverkar-1.5511
13 Chapman, S (1998)
14 I bid 26 nov 2010 5
SPin09a Linda Tysk The same thing is happening south of the area of maximum solar, trade winds are blowing
towards the low pressure area in order to equalize it, and that also causes a meeting of the cool
northern trade winds and the warmer southern summer-winds, forcing the warm air-mass to rise,
creating occlusion with growing clouds.
By the end of the winter, the area of maximum solar heating starts shifting towards the northern
hemisphere again because of Earth's tilt, resulting in increased solar heating in India warming up
the surface 15
. The heating of the land results in a created low pressure, which the atmosphere wants
to equalize by trade winds from the high pressure zone, which is the earlier low pressure zone over
the Indian ocean with moist air. That results in reversed winds blowing in over land from the ocean
that are heated up by the warm land in India (which has been heated by solar energy), leading to
extremely moist air that evaporates and form cumulonimbus clouds 16
. When to much water has been
accumulated in the clouds, it falls down as rain. In this case extreme heat, evaporation from the
ocean resulting in moist air that blows in over land and is forced to rise because of the extreme heat,
results in heavy convectional rainfall for three months during the summer (June, July and August).
Another reason to formation of clouds and heavy rainfall is when the moist air is blowing in over
land, they are forced to rise when they reach the Himalayas. When winds blow toward the
mountain, they are forced to rise over them. Eventually they reach the dew point with the result:
heavy orographic rainfall. The heavy rainfall over the south mountain-side results in huge amounts
of water-masses in streams that causes flooding in rivers in Bangladesh. The Himalayas also acts as
a wall and prevents the monsoon from reaching further in to Asia. The heavy rainfall that occurs
when the clouds reaches the Himalayas results in less moisture in the air by the time the clouds have
passed over the mountain, and when they have passed the mountain, they will start sinking again
because there is nothing pushing them upwards, and then the air heats up again and the present
moist evaporates. That leads to that the north side of the mountain is rather dry, an area that is
known as the rain shadow.
Because of the Coriolis-effect, winds blowing from the equator turns to the right. That means that
when the winds reach India, they come from south-west, thereby the name south-west monsoon.
By fall (October-November), the tilting of earth results in a movement of the ITCZ. That means that
the moist air that was blowing north is now turning towards the low-pressure that is being moved
back towards the Indian ocean again, meaning a second wind reversal. The moist air is then forced
to rise over the Himalayas again, resulting in a second monsoon called the winter-monsoon. Winds
are still forced to move in a right-bow but since they are now approaching from north they hit India
on the north-west side. But since the low pressure in India has moved south, India is not as hot as it
is during the summer, and the monsoon weakens soon after hitting the west side of India. And once
again the Himalayas acts as a wall, preventing the monsoon from reaching further than northern
The winter-season then has begun in India again, with extreme drought with moderate
temperatures and winds blowing from north to equalize the low-pressure by the Indian Ocean.
15 Chapman, S (1998)
16 I bid 17I bid 18 I bid 26 nov 2010 6
SPin09a Linda Tysk Analysis The monsoon strikes India every year, and even though it might seem like there is only negative
effects of it, there is two sides of the problem.
Every year, about 1 500 people die in southern Asia due to the monsoon 19
. And I think there are
several things that might cause deaths by a monsoon. When the summer-monsoon strikes in India,
heavy flooding occurs which results in embankments in rivers that can not hold all the water and are
overflowed. Drains in the cities can not cope with the massive amounts of water, and the heavy
flooding has many effects such as, diseases, people losing their homes and crops being destroyed.
The water-masses and flooding leads to water being polluted when dams and other water-sources
brakes, and the polluted water then becomes the only drinking source for the Indian population. The
polluted water then leads to many diseases that causes many deaths due to the Monsoon.
People also lose their homes when they're flooded, leading to huge amounts of people being
homeless. And in some cases, the monsoons were so powerful that they destroyed crops, leading to
nothing to eat and people without jobs that usually have farming as a job.
At the same time, the severe drought that strikes India each winter means that farmers rely on the
monsoons for agriculture. If monsoons wouldn't strike India, the severe drought would make it
impossible for farmers to do farming. But the the worst thing is that the farming-season depends
completely on when the monsoon strikes, because if it strikes in spring or in early summer, crops
will be destroyed since they're not done. While if it strikes in late summer would lead to a great
crop-winter when the excess water keeps land from drying, which leads to a surplus of crops where
people can sell more and get more money, which results in a growing economy.
Agriculture therefore becomes a bit like gambling, and also a part of their religion. People have
got prayers for rain, but they don't want to much rain which is impossible to control. People want
exactly the right amount of water for their crops to grow, but if the monsoon is too powerful they
have to wait till it dries, which makes it like gambling since if they sow their crops in late summer
and heavy rain strikes it, they crops are destroyed and they have to redo the sowing.
The monsoons also affect the economy and how politics is to be formed, since economy gets
affected when people lose their jobs and when agriculture is ineffective. In politics, they have to
consider how the monsoon affects the country, which means that they have to consider the major
amounts of deaths, how to rebuild everything that is destroyed and how to prevent the destruction in
I do think that the Monsoon is negative, even though the monsoon might be good for crops and
for nature, I don't think that makes up for everything that is lost when the monsoon strikes. Deaths,
poverty and people losing their homes, and since so much is lost during flooding the rebuilding
must cost a lot of money and thereby leading to people taking loans. So when agriculture is going
good and people starts earning money again, they still have to pay for what was lost earlier. I mean
that even though it happens to be positive once, it does not make up for everything that is lost when
the monsoon is negative. But people still sees it as positive because of the extreme heat and drought
that occurs during winter, so when the first rain comes, people are happy. But since nothing could
19S. Asia Monsoon. Alertnet.org. Alertnet: 28
th of September 2008
th of November 2010. http://www.alertnet.org/db/crisisprofiles/SA_MON.htm
26 nov 2010 7
SPin09a Linda Tysk be done to move India away from where it's located, there will still be drought and heavy rain. But
considering the fact that Monsoons have stricken India for hundreds of years, there should some
solution to decrease the losses each year. Such as strengthening embankments and dams to prevent
more flooding because of that.
26 nov 2010 8
SPin09a Linda Tysk Conclusion The differences and reasons why the Monsoons in Asia and especially India end up being so
destructive and heavy is because of where India is located.
India has a sub-continent, which means that there is a land-mass stretching out in the ocean from
the continent. Meaning that India is surrounded by ocean both in west, south and east. So what
makes India different is the fact that the country is located in the ITCZ, which means that the area
of maximum solar heating and winds are affected by the tilt of Earth, and thereby is located in an
area where winds switches directions throughout the year, resulting in wind reversals or Monsoons.
Extreme heat and drought is also a part of living in an ITCZ.
The ITCZ moves north and south during the year, moving the area of maximum solar heating.
Since low pressure (area with less air pressure than the surrounding areas) is created when air rises
due to either fronts meeting forcing the warmer front to lift, or because of sun-heating, clouds are
formed when the air reaches the dew point temperature/the altitude were moist in air turns into
High pressure (higher air pressure than surrounding areas) on the other hand, is an area with no
clouds (leading to drought) because air is descending when it is cooled down and therefore
evaporates the water to gas leading to no clouds.
During winter, the lITCZ is located over the Indian ocean south of India (high pressure in India).
When earth then tilts in spring, the ITCZ moves north and heats up India creating low pressure
there, winds blows from high pressure zones to equalize the pressure. The high pressure is now over
the Indian ocean and the low pressure over India, so the moist air that was evaporated over the
Indian ocean blows to India as trade winds. The moist air is heated up by the warm land in India
and heavy convectional rain occurs with flooding as result- monsoon has been created.
The Himalayas also forces moist air to rise since winds can not blow through it, leading to heavy
orographic rainfall over the Himalayas that causes flooding.
By fall, the ITCZ moves south again and winds from north blows to the created low pressure in
the Indian ocean. So once again, the moist winds reverse and blows over Himalayas causing a
winter-monsoon, but is stopped when the air descends and is heated up, ...
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Alertnet: 28th of September 2008. S. Asia Monsoon. Alertnet.org 26 th of November 2010. http://www.alertnet.org/db/crisisprofiles/SA_MON.htm Chapman, Simon (1998). Complete geography. Oxford: Oxford Univ. Press Nationalencyklopedin, hämtad 2010-11-23. Högtryck. http://www.ne.se/högtryck. SMHI: 8th of July 2009. Corioliseffekten. SMHI.se. 20th of November 2010. http://www.smhi.se/kunskapsbanken/meteorologi/corioliseffekten-1.4041 SMHI: 10th of August 2009. Hästbredderna, passadvindarna och vädret i tropikerna. SMHI.se. 20th of November 2010. http://www.smhi.se/kunskapsbanken/meteorologi/hastbredderna passadvindarna-och-vadret-i-tropikerna-1.5459 SMHI: 10th of August 2009. Lågtryck och högtryck samverkar. SMHI.se. 20th of November 2010. http://www.smhi.se/kunskapsbanken/meteorologi/lagtryck-och hogtrycksamverkar- 1.5511 Somini Sengupta: 6th July 2007. In India, a Prayer for Rain Despite a Deluge. NYTimes.com. 25th of November 2010. http://www.nytimes.com/2007/07/06/world/asia/06monsoon.html?_r=1 WorldHistoryAtYHS. Climate. WorldHistoryatYHS.org. 16th of November 2010. https://worldhistoryatyhs.wikispaces.com/Climate
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