El Niño is a weather pattern that occurs every 2-7 years in the Pacific ocean, causing significant changes in weather. It involves a rise in sea surface temperatures of at least 0.5°C in the east-central Pacific for three consecutive months. This disrupts typical wind and pressure patterns, causing warm water that normally moves westward to head east towards South America. The effects of El Niño can last 1-3 years and impact fisheries, agriculture, and precipitation patterns around the world, sometimes causing floods, droughts, wildfires or diseases in lands thousands of miles away from the Pacific. The opposite phenomenon is called La Niña.

1. El Niño and La Niña
• El Niño is a series of complex weather patterns that occurs every 2-7 years. It causes
drastic changes in weather.
• This occurs in pacific oceanic region.
• If SST rises for 0.50
C for three consecutive months and changes in atmospheric
conditions and rainfall patterns called El Niño.
• Surface winds across most of the tropical Pacific normally move from east to west. The
trade winds blow from the normally high-pressure area over the eastern Pacific (near
central and South America) to the normally stable low-pressure area over the western
Pacific (north of Australia).
• Pressure areas change places at high pressure builds in the western Pacific, and low
pressure dominates the eastern Pacific. Winds across the tropical Pacific then reverse
direction and blow from west to east—the trade winds weaken or reverse.
• This change in atmospheric pressure (and thus in wind direction) is called the
Southern Oscillation.
• warmer water normally travelled westward now moving towards the east. The
eastward-moving warm water usually arrives near the South American coast around
Christmas time. In the ocean warm water pushed colder water downward blocking the
important upwelling from colder water from the bottom.
• The phenomena of the Southern Oscillation and El Niño are coupled, so the terms are
often combined to form the acronym ENSO. effects of ENSO can be last longer for 1yr
or more than 3 yrs.
• This effects to marine life to migrate to colder waters. this cause fisheries decreasing in
central and south America.
• Moisture then rises in to the air and effects of El Niño is felt throughout the America.
• The effects are felt not
only in the Pacific; all
ocean areas at trade wind
latitudes in both
hemispheres can be
affected.
• Most significant
upwelling region that
Peru Current is
interrupted or overridden
by the warm water.
• During major ENSO
events, sea level rises in
the eastern Pacific,
sometimes by as much as
20 centimeters (8 inches) in the Galápagos. Water temperature also increases by up to
7°C

2. • But El Niño most activities on land.
In the central and south America
warm air and moisture increase and
lead to storms, rainfall and that can
lead to billions of dollars in damages,
high death tolls, and diseases like
malaria even the places that they are
not normally occurs.
• In the southeast Asia and Australia,
the opposite takes place. these are
suffering from draught, wildfire and
colder ocean waters.
• If Positive IOD correlated with the El
Nino effect. This will lead a very arid
condition in the Eastern part of the
Indian ocean
• The trade winds blow from the high-
pressure area over the eastern Pacific
and upwelling on that region to the
stable low-pressure area over the
western Pacific keeping downwelling
and this is called as Walker
circulation.
• This is caused because strong trade
winds. this drives reverse conditions
of El Niño. this will leads flood,
tropical cyclones cyclones, in
northeastern Australian coast. This
warm water will leeks through
Indonesian region and supercharge
Leeuwin currents.
• If Negative IOD correlated with La
Nina effect.
most parts
of the
Australia
will be with
heavy rains
and storms
will result
flooding.