Japanese weather agency: La Nina is over
Japan's weather agency says the La Nina phenomenon that caused last year's record hot summer in Japan and severe cold in January apparently ended by April.
La Nina is a weather condition in which surface temperatures fall below average in the eastern Pacific Ocean near the equator off Peru. The condition is known to affect global weather.
The agency said on Wednesday that the phenomenon started last summer for the first time in 3 years but that temperatures had returned to normal by April.
But the agency forecasts another hot summer this year in Japan, citing higher temperatures in recent years, mainly due to global warming.
It says this summer will not be as hot as last year's, but is advising caution against heatstroke.
Wednesday, May 11, 2011 20:28 +0900 (JST)
La Niña near its end
Issued on Wednesday 11 May | Product Code IDCKGEWWOO
The 2010−11 La Niña event is nearing its end, with most indicators approaching neutral values. Climate models surveyed by the Bureau of Meteorology suggest that the Pacific Ocean will continue to warm over the coming months, with neutral conditions likely to persist through the austral winter.
Steady warming of the equatorial Pacific Ocean since mid-January has resulted in near-normal ocean temperatures. Atmospheric indicators of La Niña are now responding to these changes in the ocean and an active Madden Julian Oscillation, resulting in a weakening of trade winds, changes in cloudiness and an easing of typical La Niña pressure patterns. Likewise, the Southern Oscillation Index (SOI), which recorded its highest April value since 1971, has dropped from above +25 to +11 in the past fortnight.
The influence of the Indian Ocean Dipole (IOD) on Australian rainfall is currently neutral. A weakly positive IOD event has been forecast to develop during winter. In the past, positive IOD events have been associated with drier conditions over parts of Australia, particularly in the south east, during the winter and spring seasons.
http://www.bom.gov.au/climate/enso/
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Climatehttp://www.physorg.com/news/2011-02-climate-phenomenon-la-nina-blame.html
phenomenon La Nina to blame for global extreme weather events
February 7, 2011Enlarge
Cyclone Yasi over Australia in February 2011. Image credit: NASA
(PhysOrg.com) -- Recent extreme weather events as far as Australia and Africa are being fueled by a climate phenomenon known as La Nina -- or "the girl" in Spanish. La Nina has also played a minor role in the recent cold weather in the Northeast U.S.
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Scientists at the International Research Institute for Climate and Society (IRI), part of Columbia’s Earth Institute, expect moderate-to-strong La Niña conditions to continue in the tropical Pacific, potentially causing additional shifts in rainfall patterns across many parts of the world in months to come.
These shifts, combined with socioeconomic conditions and other factors, are making some countries more vulnerable. However, La Niña and El Niño conditions actually allow for more accurate seasonal forecasts and help better predict extreme drought or rainfall in some areas. That’s because they affect global atmospheric circulation patterns in known ways, and scientists can use this knowledge to help societies prepare better, issue early warnings and reduce any negative impacts associated with them.
"Based on current observations and on predictions from models, we see at least a 90 percent chance that La Niña conditions will continue through March," said IRI's chief forecaster, Tony Barnston.
Climate scientists have found La Niña's fingerprints on a number of extreme weather events such as the devastating flood that occurred in Pakistan in 2010, as well as flooding in West Africa, South Africa and most recently in Queensland, Australia, where an area equal to the combined size of France and Germany was underwater. La Niña is also to blame for Cyclone Yasi, one of the strongest to hit Australia, which came ashore on Feb. 2. Cyclone Yasi is the second most damaging Australian cyclone on record after Cyclone Tracy, which struck in 1974.
But La Niña isn't to blame for the recent severe weather affecting the Northeast. Winter weather for these regions is often driven not by La Niña but by large-scale weather patterns over the U.S., the northern Atlantic Ocean and the Arctic. These are often short-term, and are generally predictable only a week or so in advance. They are the culprits responsible for the dip in temperatures and spike in snow storms in the Midwest and Northeast.
In addition to extreme rainfall, La Niña can lead to drought conditions. Currently in East Africa, it has caused drier-than-usual weather, sparking food-security concerns in areas lacking irrigation, including parts of Somalia, Kenya, Ethiopia and Tanzania. Parts of South America, Asia and the southern U.S. may also see lower rainfall for the first quarter of 2011.
Since 1950, the world has experienced six major La Niña events, wreaking havoc in countries around the world. In 2000, for example, floods associated with La Niña affected 400,000 people in southern Africa, caused at least 96 deaths and left 32,000 homeless.
La Niña conditions typically persist for 9 to 12 months, peaking sometime during the end of the year. But 2010 was a lively year for climate scientists: For the first four months of this year, El Niño conditions prevailed in the tropical Pacific, but that quickly changed, and by June, a La Niña pattern had emerged.
"Last year's transition from El Niño to La Niña was about the most sudden we've ever had," Barnston said. "When we had rapid flips like this in the past, we sometimes ended up having a two-year La Niña, such as right after the El Niño episodes of 1972 to 1973 and 1997 to 1998."
Barnston cautions that the likelihood of this happening with the current La Niña is unknown. "Even if we do have a second year of La Niña developing in northern summer 2011, we expect at least a brief return to neutral conditions from May to July of 2011."http://www.guardian.co.uk/environment/2011/jan/11/australia-floods-...
la nina was blamed for the autralian floods this year
Australia floods: La Niña to blame
The devastating flooding in Queensland is the result of Australia being in the grip of an unusually strong "La Niña", a periodic climate phenomenon that brings more rain to the western Pacific, and less to South America along the eastern Pacific.
"The Queensland floods are caused by what is one of the strongest – if not the strongest – La Niña events since our records began in the late 19th century," said Prof Neville Nicholls at Monash University and president of the Australian Meteorological and Oceanographic Society. "The La Niña is associated with record warm sea-surface temperatures around Australia and these would have contributed to the heavy rains." Warmer oceans produce damper air and hence more rain. This is driven onshore by the stronger east-to-west trade winds characteristic of La Niña.
These weather patterns led to December being the wettest ever recorded in Queensland and to Australia having its third wettest year. The Australian Bureau of Meteorology predicts that La Niña is likely to persist into the southern hemisphere autumn, raising the possibility of further torrential downpours.
La Niña, "the girl" in Spanish, is named in reference to its counterpart, El Niño – "the Christ Child". Here the climatic conditions are reversed, with warmer, wetter weather over South America which is usually first noticed at Christmas by fishermen off Peru. La Niña occurs at intervals between a few years and a decade and generally lasts for a year or two. What causes the switch is not known, but it is thought to arise from the complex interaction of ocean and atmospheric circulations.
"This is one of the strongest La Niña events in the past half century," said Bill Patzert, a climatologist at Nasa's Jet Propulsion Laboratory. "Impacts include heavy rains and flooding, which has damaged crops and flooded mines in Australia and Asia. It also has resulted in flooding in northern South America and drought conditions in Argentina. This powerful little lady is spreading her curses and blessings across the planet. She's the real deal."
A silver lining in the storm clouds brought by La Niña is the relief of the decade-long drought much of Australia has endured. There was a dramatic recovery in water storages across the Murray-Darling Basin in eastern Australia from 26% full at the start of 2010 to 80% at the start of 2011. However, elsewhere in the country, south-western Australia suffered its driest year on record in 2010, continuing decades of drying.
"The extent to which any of this – the floods, warm oceans, or very strong La Niña – is linked to global warming is unknown, because the requisite studies to test this have simply not been done yet," said Nicholls.
But as a general point, said Prof Vicky Pope, head of climate change advice at the Met Office, a warmer world is a wetter world. "As the average global temperature increases one would expect the moisture content of the atmosphere to rise, due to more evaporation from the sea surface. For every 1C sea surface temperature rise, atmospheric moisture over the oceans increases by 6-8%. Also in general, as more energy and moisture is put into the atmosphere [by warming], the likelihood of storms, hurricanes and tornadoes increases."
The country is in the in the grip of an unusually strong periodic climate phenomenon that brings heavy rains