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\section*{Blog - El Niño project (part 1)}

This is a [[Blog articles in progress|blog article in progress]], written by [[John Baez]]. To see discussions of the article as it was being written, visit the \href{http://forum.azimuthproject.org/discussion/1368/blog-el-nino-project-part-1/}{Azimuth Forum}.

If you want to write your own article, please read the directions on \href{http://www.azimuthproject.org/azimuth/show/How+to#blog}{How to blog}.

A bunch of Azimuth Project members like to program, so they started the  has been around for a while\ldots{} but now it's getting more lively! We're trying to understand and predict the climate phenomenon known as .

Why? Several reasons:

$\bullet$ It's the biggest source of variability in the Earth's climate on times scales between a year and a decade. It causes weather disturbances in many regions, especially near the Pacific Ocean. The last really big one happened in 1997-1998, and we're waiting for the next.

$\bullet$ It's hard to predict for more than 6 months in advance. It's not periodic: it's a  phenomenon that occurs across the tropical Pacific Ocean every 3 to 7 years.

$\bullet$ It matters for global warming. A lot of heat gets stored in the ocean, and a lot comes back into the atmosphere during an El Ni\~n{}o. So, the average surface air temperature of the Earth may reach a new high when the next El Ni\~n{}o comes.

$\bullet$ In February 2014,  in  caused a stir by claiming to be able to predict the next El Ni\~n{}o more than 6 months in advances using ideas from network theory. Moreover, it claimed an El Niño would start in late 2014 with a 75\% probability.

$\bullet$ The math involved in this paper is interesting, not too complicated, and maybe we can improve on it. At the very least, it raises a lot of questions worth studying. And it's connected to network theory, one of the Azimuth Project's specialties!

We are already  on this project. We could use help from computer programmers, mathematicians, and physicists: there is lots to do! But it makes sense to start by explaining the issues and what we've done so far. We'll do that in a series of posts here.

This first post will not get into many details. Instead, I just want to set the stage with some basic information about El Ni\~n{}o.

This animation produced by the  shows how the cycle works:

During  years, trade winds blow across the Pacific Ocean from the Americas to Asia in a strong way. So, warm surface water gets pushed toward Asia. Warmer oceans there create more clouds and rain there. The other side of the Pacific gets cooler, so there is less rain in many parts of the Americas.

During  years, trade winds in the tropical Pacific weaken, and blobs of warm surface water move back toward the Americas. So, the eastern part of the Pacific warms up. We generally get more rain in the Americas\ldots{} but less in Asia.

The cycle of El Ni\~n{}os and La Ni\~n{}as is often called the  or . Why? Because this cycle is linked to the : an oscillation in the difference in air pressure between the eastern and western Pacific:

The top graph shows variations in the water temperature of the tropical eastern Pacific ocean: when it's hot we have an El Ni\~n{}o. The bottom graph shows the air pressure in Tahiti minus the air pressure in Darwin, Australia --- up to a normalization constant, this called the , or . If you stare at the graphs a while, you'll see they're quite strongly correlated---or more precisely, , since one tends to go up when the other goes down. So, remember:

There are other ways besides the SOI to tell if an El Ni\~n{}o is happening. We'll talk later about these quantities, how they're defined, how you can get the data online, what we've done with this data, and what we want to do.

To conclude now, I just want you to watch this short movie. NASA's Jason-2 satellite has detected blobs of hot water moving east toward America! This has made some scientists---not just those using network theory---suspect a big El Ni\~n{}o is on its way, perhaps a repeat of the one that started in 1997.

link: {\colorbox[rgb]{1.00,0.93,1.00}{\tt \char60object\char32width\char61\char34\char53\char54\char48\char34\char32height\char61\char34\char51\char49\char53\char34\char62\char60param\char32name\char61\char34movie\char34\char32value\char61\char34\char47\char47www\char46youtube\char46com\char47v\char47zaxPwASV\char50kY\char63hl\char61en\char95US\char38amp\char59version\char61\char51\char34\char62\char60\char47param\char62\char60param\char32name\char61\char34allowFullScreen\char34\char32value\char61\char34true\char34\char62\char60\char47param\char62\char60param\char32name\char61\char34allowscriptaccess\char34\char32value\char61\char34always\char34\char62\char60\char47param\char62\char60embed\char32src\char61\char34\char47\char47www\char46youtube\char46com\char47v\char47zaxPwASV\char50kY\char63hl\char61en\char95US\char38amp\char59version\char61\char51\char34\char32type\char61\char34application\char47x\char45shockwave\char45flash\char34\char32width\char61\char34\char53\char54\char48\char34\char32height\char61\char34\char51\char49\char53\char34\char32allowscriptaccess\char61\char34always\char34\char32allowfullscreen\char61\char34true\char34\char62\char60\char47embed\char62\char60\char47object\char62}}

On the other hand, on June 17th the National Oceanic and Atmospheric Administation (NOAA) said that trends are now running . So we'll have to wait and see\ldots{} and meanwhile, try to predict!

If you can't wait to dive in, start here:

$\bullet$ , Azimuth Forum.

To join this conversation, join the forum by following these instructions:

$\bullet$ .

This is the paper that got us excited:

$\bullet$ Josef Ludescher, Avi Gozolchiani, Mikhail I. Bogachev, Armin Bunde, Shlomo Havlin, and Hans Joachim Schellnhuber, Very early warning of next El Niño, , February 2014.

It's not yet freely available, but a lot of the methodology comes from this free paper:

$\bullet$ Josef Ludescher, Avi Gozolchiani, Mikhail I. Bogachev, Armin Bunde, Shlomo Havlin, and Hans Joachim Schellnhuber, , , 30 May 2013. (For more discussion, .)

category: blog, climate

[[!redirects Blog - El Nino project (part 1)]] [[!redirects El Nino project (part 1)]]



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