enso and its impact

7/29/2019 ENSO and Its Impact

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ENSO AND ITS IMPACT ON TROPICALCYCLONES


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ENSO El Nino + Southern oscillation or El Nino/La Nina/Southern

oscillation refers to variations in the temperature of the surface ofthe tropical eastern Pacific Ocean and in air surface pressure in thetropical western Pacific.

A climatic pattern that occur in the Pacific ocean once in roughlyfour or five years. El Nino and La Nina represent opposite extremesin the naturally occurring climate cycle referred to as the ElNino/Southern Oscillation (ENSO).

Tahiti, Peru and Darwin in Australian coast are the areas where the

surface air pressure difference determine the Southern oscillation


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Southern Oscillation Index

[ Pdiff- Pdiffav ]

SOI = 10 x -----------------

SD(Pdiff)

SOI ranges from -35 to 35

When SOI is positive then normal conditions will prevail

When SOI is negative then El Nino conditions will

prevail


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Normal Conditions in Pacific

Normally the water in the tropical western Pacific is muchwarmer (about 8Celsius) than the water off the shore of Peru

and Ecuador.

Therefore there is lower air pressure over the West Pacific and

this results in the emergence of clouds and heavy rains, like

they are common in south-east Asia and northern Australia. As the trade winds blow from East to West, they transport the

warmer surface water westwards, therefore making place for

colder waters from the depths of the sea.

In the East Pacific the water is colder, therefore the air

pressure higher. This situation leads to relatively drycircumstances at the South-American coastline.


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Normal Conditions in Pacific

SOI=+1 to +5Source: http://www.pagasa.dost.gov.ph


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El Nino Conditions From time to time a huge warm water flow arises around the

coasts of Ecuador, Peru and Northern Chile, causingmassive weather changes around the world.

This phenomenon also called El Nino, meaning The ChristChild, represents the largest so far known disturbance of theglobal weather conditions.

An El Nino season is marked by a fading or even aninversion of the trade winds.

Warm water flows from the West Pacific eastwards, forging asignificant rise in the temperature of the surface water off thewestern coast of South-America.

The humid conditions, which normally dominate in the West

Pacific shift to the East and the arid situation, whichcontrols the climate in the eastern pacific, arises in the West.

Therefore rainfalls with associated flooding are encounteredin Peru and droughts in Australia.


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ContdThe first signs of an El Nio are: Rise in surface pressure over the Indian

Ocean, Indonesia, and Australia Fall in air pressure over Tahiti and the rest of the

central and eastern Pacific Ocean Trade winds in the south Pacific weaken or head east Warm air rises near Peru, causing rain in the northern

Peruvian deserts Warm water spreads from the west Pacific and

the Indian Ocean to the east Pacific. It takes the rainwith it, causing extensive drought in the westernPacific and rainfall in the normally dry eastern Pacific.


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El Nino Conditions

Source: http://www.philonline.com/~cab


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La nina conditions in Pacific

The name La Nina, meaning LittleGirl in English,

has been given to it, because of its opposition to ElNio. Sometimes it is also called El Viejo, meaningTheOld.

Although emerging from the exact opposite climaticconditions than El Nino, La Nina nevertheless

causes abnormal and extreme weather conditionsin the Southern Pacific area.

When it occurs the surface water in the EasternPacific cools down below average.

As a result the trade winds blow faster and thisleads to an increase in the upwelling of coldnutrient rich waters near the South American WestCoast.


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Contd In the past El Nio and La Nia appeared well

balanced, but the amount of damage caused by La

Nia is significantly smaller than this caused by El

Nio.

Compared to it's brother event, La Nia causes

vastly less natural disasters. That's the reason why

El Nio always casts a shadow on his little sister

and why people are not nearly as afraid of La Nia

than of El Nio.


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La Nina in Pacific Conditions

Source: http://www.philonline.com/~cab


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La Nina in Pacific Conditions

[Source: http://www.pmel.noaa.gov/tao/elnino/nino-home.html]


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Indian cyclones and ENSO La Nina and El Nino events has found that El Nino/La Nina-

Southern Oscillation (ENSO) significantly influenced thefrequency, genesis and intensity of cyclones in the Bay ofBengal.

According to the scientists, so far 20 devastating cyclones had

occurred in India. 10-La nina and 9-El nino phase, but solidproof or establishment need to be made.

Increased speed of Wind in the pacific ocean during La ninaperiod will make the Indonesian ocean sea surfacetemperature to rise and thereby affecting the temperature ormaking the BOB warmer. With the Ocean getting heated up,the intensity of cyclones will increase in BOB

Also found that genesis got shifted.


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Contd The importance of Cyclones from AB got attention after 2 cyclones

of 2007-relation with ENSO analyzed-SST analysis by satellitemonitoring-sharp increase in SST since 2000-during strongest Elnino year (1997-98) and (1982-1983)-SST also touched newhigh.

Both BOB and AB shows higher SSTs during La Nina phases.


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Climate Change and ENSO With the increasing studies on climate change, the frequency of

occurrence of El Nino and La Nina is found to change abruptly.

No prior prediction facility

Only predicted after onset

As 25% of Worlds climate determined by Pacific ocean many

countries are found to be affected by it

Drought conditions of Australia coincide with that of India

Increased intensity of Cyclones and occurrence in India.


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REFERENCE

http://www.pmel.noaa.gov/tao/elnino/nino-home.html

accessed on 24

th

October 2011 http://www.pmel.noaa.gov/tao/jsdisplayaccessed on 25th

October 2011

http://iridl.ldeo.columbia.edu/maproom/.ENSO/.Time_Serie

s/SOI.html accessed on 25th October 2011

http://iridl.ldeo.columbia.edu/maproom/.ENSO/.Time_Series/SOI.html accessed on 24th October 2011

http://www.imdpune.gov.in/ncc_rept/RESEARCH%20REPORT%204.pdf

accessed on 27th October 2011

http:// www.enotes.com ScienceWorld of Earth Science accessed on

28th October 2011 http://geography.about.com/od/globalproblemsandissues/a/elninolanina.

htm accessed on 26th October 2011
http://www.pmel.noaa.gov/tao/elnino/nino-home.htmlhttp://www.pmel.noaa.gov/tao/jsdisplayhttp://iridl.ldeo.columbia.edu/maproom/.ENSO/.Time_Series/SOI.htmlhttp://iridl.ldeo.columbia.edu/maproom/.ENSO/.Time_Series/SOI.htmlhttp://iridl.ldeo.columbia.edu/maproom/.ENSO/.Time_Series/SOI.htmlhttp://iridl.ldeo.columbia.edu/maproom/.ENSO/.Time_Series/SOI.htmlhttp://www.imdpune.gov.in/ncc_rept/RESEARCH%20REPORT%204.pdfhttp://www.imdpune.gov.in/ncc_rept/RESEARCH%20REPORT%204.pdfhttp://www.google.co.in/url?url=http://www.enotes.com/science&rct=j&sa=X&ei=NDmlTo7LFMvprQebybHcAg&ved=0CCAQ6QUoADAA&q=el+nino+and+la+nina+phenomenon&usg=AFQjCNFgSm9y-fAWUxLXu89VIXj_tXEfiQhttp://www.google.co.in/url?url=http://www.enotes.com/earth-science&rct=j&sa=X&ei=NDmlTo7LFMvprQebybHcAg&ved=0CCEQ6QUoATAA&q=el+nino+and+la+nina+phenomenon&usg=AFQjCNHB-cc_sTpKeHlkA5B89Y_VlNL5jAhttp://geography.about.com/od/globalproblemsandissues/a/elninolanina.htmhttp://geography.about.com/od/globalproblemsandissues/a/elninolanina.htmhttp://geography.about.com/od/globalproblemsandissues/a/elninolanina.htmhttp://geography.about.com/od/globalproblemsandissues/a/elninolanina.htmhttp://www.google.co.in/url?url=http://www.enotes.com/earth-science&rct=j&sa=X&ei=NDmlTo7LFMvprQebybHcAg&ved=0CCEQ6QUoATAA&q=el+nino+and+la+nina+phenomenon&usg=AFQjCNHB-cc_sTpKeHlkA5B89Y_VlNL5jAhttp://www.google.co.in/url?url=http://www.enotes.com/science&rct=j&sa=X&ei=NDmlTo7LFMvprQebybHcAg&ved=0CCAQ6QUoADAA&q=el+nino+and+la+nina+phenomenon&usg=AFQjCNFgSm9y-fAWUxLXu89VIXj_tXEfiQhttp://www.imdpune.gov.in/ncc_rept/RESEARCH%20REPORT%204.pdfhttp://www.imdpune.gov.in/ncc_rept/RESEARCH%20REPORT%204.pdfhttp://iridl.ldeo.columbia.edu/maproom/.ENSO/.Time_Series/SOI.htmlhttp://iridl.ldeo.columbia.edu/maproom/.ENSO/.Time_Series/SOI.htmlhttp://iridl.ldeo.columbia.edu/maproom/.ENSO/.Time_Series/SOI.htmlhttp://iridl.ldeo.columbia.edu/maproom/.ENSO/.Time_Series/SOI.htmlhttp://www.pmel.noaa.gov/tao/jsdisplayhttp://www.pmel.noaa.gov/tao/elnino/nino-home.htmlhttp://www.pmel.noaa.gov/tao/elnino/nino-home.htmlhttp://www.pmel.noaa.gov/tao/elnino/nino-home.html


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enso and its impact

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