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23

First, to describe El Niño as a Pacific Ocean event seems overly simplistic. The effects of El Niño are felt worldwide as can be seemed by a principal component (EOF) analysis (e.g., Alexander et al., 2002). Also, using the term "El Niño" to describe the entire oscillation (ENSO, El Niño Southern oscillation) can lead to confusions as the term "El Niño" ...


10

All season forecast systems are subject to uncertainty. The uncertainty arises from an imperfect initial state, such as initial conditions, and from imperfect models, such as uncertainty due to, numerical methods, parametric models, data sampling. Forecasting systems utilize ensembles and their spread to quantify uncertainty. See the spread in forecasts ...


10

Great question. These features are mesoscale Eddies and they are akin to hurricanes in the atmosphere. They are the ocean’s high or low pressure systems and are the result of instabilities. The cyclonic eddy (counterclockwise direction in the northern hemisphere) is called a cold-core eddy and the anti-cyclonic eddy is called a warm-core eddy. Unlike ...


10

Here is a nice picture from Ashok & Yamagata (2009): It seems like the Kelvin wave is held back for some reason that I am not familiar with. From the figure below it looks analogous to a standing wave vs a freely propagating wave. Interestingly, some authors argue that the frequency of these events has increased in recent years for anthropogenic ...


8

There is a case study from Environmental Science entitled El Niño: A Link among Atmospheric, Oceanic, and Crustal Circulation? that discusses the correlations between seismic activity and El Niño cycles in certain areas of the world, that have been documented: A geophysicist, Daniel A. Walker, hypothesizes that a different sequence of events produces an ...


6

I think it is important to think of the El Niño as just one of the components of a large scale global atmospheric-oceanic phenomenon known as the El Niño and the Southern Oscillation (ENSO). ENSO takes shape as fluctuations of the rainfall, wind, ocean currents and waves. They are by nature very irregular. The Southern Oscillation (SO) was first discovered ...


6

The large scale modes of variability present in the atmosphere are also found in the ocean. There is a strong feedback between the two systems with wind, heat flux and atmospheric pressure modifying ocean surface conditions and with parameters such as sea surface temperature altering atmospheric conditions. A lot of studies have explored teleconnections in ...


6

I'm not sure if it's correct to say that El Niño enhances the jet stream, reading NWS they seem to state that the affect is more of a shift in the position of the jet stream over the Pacific and North America. I guess any enhancement would be due to a greater temperature contrast between the poles and equator.


5

One issue here is whether El Niño (ENSO) is chaotic in nature. There is a fair amount of literature on the chaotic and deterministic nature of ENSO (e.g., https://www.sciencemag.org/content/264/5155/72.abstract, http://onlinelibrary.wiley.com/doi/10.1029/97GL53639/full). Under the chaotic assumption, the posted question might not have a clear answer. Then ...


5

During El Niño heat is transferred from ocean to atmosphere. If atmosphere gets warmer, yes, it generates more radiation and more heat escapes into space. The same about land surface - if it's warmer, it radiates more heat. Of course that's all with assumption that there are no other factors influencing it - like e.g. greenhouse gases.


5

If you look at the ENSO index record, you can see many instances of El Niño or La Niña occurring multiple times in a row. For instance, the period 1977-1983 and even after that is a succession of El Niño events with normal conditions in between and no La Niña period. Multivariate ENSO Index (MEI) from NOAA


4

I'm posting this as an answer rather than a comment to expand a bit on the excellent answer from Isopycnal Oscillation and note some minor differences I observed. I had actually looked for temperature and temperature anomaly differences in the middle of the eddies and didn't see them prior to posting the question so it didn't look like upwelling at first. ...


4

Just to expand on the answer by @Siv: Previous studies have indeed suggested teleconnections between the jet stream and ENSO (for example: Horel 1981). Recall that, at a fundamental level, the jet stream (a westerly geostrophic wind pattern) is driven by horizontal North-South temperature gradients across cold and warm air masses (thermal wind). Thus, it ...


3

The best article about the 1789-1793 El Niño is probably Grove (1998) Nature study. There is also a lot more information in Grove's 2007 paper. In the second paper, he explores the global consequences of the El Niño event (some evidence is mostly circumstantial), which he describes as being quite severe: famine ("By November 1792 over 600,000 deaths were ...


2

By definition, El Niño and La Niña cannot occur at the same time. They are instead opposite extreme phases of the El Niño Southern Oscillation. El Niño conditions occur when the average temperature of the Niño 3.4 region is a half degree or more over the average for three consecutive months or more. La Niña conditions occur when the average temperature is a ...


1

First, based on the ONI, there are El Niño and La Niña periods, not necessarily years. For example, 2016 was El Niño during the first half and La Niña during the second half. On the flip side, From summer 1998 to early 2001 was one continuous La Niña period. Second, The The wording that the NOAA gives for official classification of El Niño and La Niña ...


1

Still undetermined, though a number of papers on the subject suggest global warming will increase the variance in both of the climate systems you mention. They suggest more research and more refined models are needed to narrow down the uncertainties. Some definitions: The Madden-Julian Oscillation (MJO) is the major fluctuation in tropical weather on ...


1

Central Pacific El Niños have different effects than Eastern Pacific El Niños. For example, Modoki El Niño tends to have more hurricanes in Atlantic and Gulf of Mexico regions. Modoki El Niños may have been around going back to the 13th century, possibly before. The El Niño which developed in 2015 is a Modoki version of the phenomenon.


1

As explained on slide 9 of Dr. William S. Kessler's talk The warm water pool in the western (Asian) pacific drains eastward and toward the poles. This causes the thermocline in the western pacific to get closer to the surface, which in turn cools the surface temperature in the western pacific, ending the El Niño.


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