2. WhatisLaNiña?
La Niña is characterized by unusually
cold ocean temperatures in the
Equatorial Pacific.
3. QuickfactsaboutLaNiña
The phrase "La Niña" is spanish for "the
girl".
Unusually cold ocean temperatures in the
equatorial Pacific.
La Niñas appear approximately every 4-5
years. They typically last 1-2 years.
Global climate abnormalities of La Niña
are less pronounced.
The effects of La Niña are not always
4. Natural phenomenon in the climate
system
Have been occurring for centuries.
Detailed observations from ships led to
systematic instrumental record keeping
in the earlier half of this century.
After an El Niño, the climate does not
always swing to a La Niña phase.
There have been only 17 moderate to
strong La Niñas compared to 25
moderate to strong El Niños in the
century.
5. BriefhistoryofLaNiñaterms
At the turn of this century, a connection
between La Niña, El Niño, and other
weather patterns had yet to be established
During the 1920s, the head of the Indian
Meteorological Service, Sir Gilbert Walker,
recognized patterns to the rainfall in South
America.
He theorized additional associations with
the change in the ocean temperatures, and
with atmospheric pressure changes
measured at stations at different parts of the
Pacific.
6. WhyLaNiñaOccurs?
occur due to increases in the strength of
the normal patterns of trade wind
circulation.
Under normal conditions, these winds
move westward, carrying warm surface
water to Indonesia and Australia and
allowing cooler water to upwell along the
South American coast.
For reasons not yet fully understood,
periodically these trade winds are
strengthened, increasing the amount of
cooler water toward the coast of South
8. The increased amount of cooler water toward the coast
of South America, causes increases in the deep cloud
buildup towards southeast Asia.
Resulting in wetter than normal conditions over
Indonesia during the northern hemisphere winter.
The changes in the tropical Pacific are accompanied by
large modulations of the jet stream within the middle
latitudes, shifting the point at which the stream
normally crosses North America. The shifted jet
stream contributes to large departures from the
normal location and strength of storm paths. The
overall changes in the atmosphere result in
temperature and precipitation anomalies over North
America which can persist for several months.
12. There was a relatively strong La Niña episode during 1988–
1989.
La Niña also formed in late 1983,in 1995, and a protracted La
Niña event that lasted from mid-1998 through early 2001.
This was followed by a neutral period between 2001 and
2002.
The La Niña which developed in mid-2007 and lasted until
almost 2009, was a moderate one.
The strength of La Niña made the 2008 Atlantic hurricane
season.
A new La Niña episode developed quite quickly in the eastern
and central tropical Pacific in mid-2010,and lasted until early
2011.
It intensified again in mid-2011 and lasted until early 2012
.This LaNiña, combined with record-high ocean temperatures
13. The same La Niña event is also a likely cause
of a series of tornadoes of above-average
severity that struck the Midwestern and
Southern United States in the spring of 2011,
and is currently a major factor in the drought
conditions persisting in the South Central
states including Texas, Oklahoma and
Arkansas.
Meanwhile, a series of major storms caused
extensive flooding in California in December
2010, with seven consecutive days of non-stop
rainfall, leading to one of the wettest
Decembers in over 120 years of records. This
is in contrast to the drier-than-normal
conditions typically associated with La Niña
in California.
14.
15. Whataretypicalglobalclimateeffects?
ImpactsonPrecipitationandTemperature
As La Niña conditions developed after mid-year,
global rainfall patterns started to adjust, especially in
the tropics.
By October, global rainfall patterns consistent with
the developing La Niña conditions were first observed
in the far western Pacific and, as the cold episode
developed, characteristic La Niña patterns were
observed elsewhere.
These included relatively wet conditions over much
of Indonesia and parts of Australia and southern
Africa, and relatively dry conditions in south-eastern
South America, including parts of southern Brazil,
Uruguay, Northern Argentina, and much of eastern
16. TypicalLaNiñaImpacts
La Niña tends to bring nearly opposite effects
of El Niño to the United States — wetter than
normal conditions across the Pacific
Northwest and dryer and warmer than normal
conditions across much of the southern tier.
The impacts of El Niño and La Niña at these
latitudes are most clearly seen in wintertime.
During a La Niña year, winter temperatures
are warmer than normal in the Southeast and
cooler than normal in the Northwest.
19. Forecasts
Computer models and statistical methods,
along with, ocean and atmosphere measuring
devices such as moored and drifting buoys and
satellites, are used to accurately predict the arrival
of El Niño or La Niña.
The buoy measurements are part of an
international research program Tropical Ocean
and Global Atmosphere (TOGA).
This program is designed to study naturally
occurring climate change and variation that
results from interaction between the tropical
ocean and global atmosphere
20.
21. DetectionandPrediction
satellites, moored ATLA and PROTEUS buoys,
drifting buoys, sea level analysis
For short term prediction (up to 1 year) of
climate variations, current observation in the
Tropical Pacific are vital.
Numerical models are used in many places.
22. LA NinaTheme Page
http://www.pmel.noaa.gov/tao/elnino/nino-home.htm
la Niña: online meteorology guide
http://ww2010.atmos.uiuc.edu/(Gh)/guides/mtr/eln/ho
me.rxml
Contents - la Niña
http://www.msc-smc.ec.gc.ca/education/elnino/index
El Niño/La Niña Update
http://www.wmo.ch/nino/updat.html#intro
