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We've heard a great deal about El Nino of late .... possibly because those of us here in the Northeast have experienced two fairly severe winters after several mild ones. And without going into personal opinions, I tend to think that the subject has gained attention in part because the debate over climate change (or global warming, if you prefer) simply no longer resonates as strongly as was previously the case.
Before going any further, I want to add that I had one non-technical college Meteorology course, in the winter of 1967-68; neither El Nino, nor any serious discussion of long-term climate change was raised at that time; I first heard the term itself in the winter of 1976-77, which was characterized by a prolonged period of cold in the Northeast and a mild winter on the West Coast. At that time, El Nino was "described" essentially as a strong warm current in the Eastern Equatorial Pacific that was believed to affect the severity of seasonal climate variances ... but not much more; at least in terms of what could be easily explained to a non-technical public.
The occasional mention of El Nino continued for several years, and I think that several other notably-cold winters through the mid-1980's may have been a factor. But as time wore on, the incidence of such references continued to decline -- particularly notable, from my viewpoint, because the emergence of 24/7 cable weather channels should have inveighed in favor of greater public exposure. (And it's also interesting to me that a perusal of the historical origins of the term can trace it back to the 1890s, although another severe winter in 1982-83 is cited as fueling a resurgence in interest within the scientific community).
It's perhaps fitting that the often-used observation that "Everybody talks about the weather, but nobody does anything about it." is usually attributed to Mark Twain, and occasionally to Benjamin Franklin, when it was actually a contemporary of Twain's, fellow author Charles Dudley Warner, who actually coined the phrase. And the point I really want to make here is that one only needs to spend a few minutes with the Weather Channel to recognize that its managers know that subtle-but-constant insecurity is a more effective salesman than "business as usual".
So with the onset of another winter now only days away, and with the last major surge of interest in the phenomenon of El Nino now several decades behind us, I'd like to see some serious input from the professionals among us as to how much of this year's discussion can be viewed in the light of fact, particularly those facts which have come to light since the late Seventies ... and how much might be just hot air (or warm water)?
Last edited by 2nd trick op; 11-08-2015 at 08:01 PM..
Do you want an explanation of what El Niño is and its effects or is there a more specific question? The second half of your OP is rather rambly and not all that weather related.
The last major mention of El Niño was the 1997-1998, which was the last major one. It was all over the news. In any case, it's late but I'll write my own summary of what El Niño does if someone doesn't beat me to it.
the winter of 1976-77, which was characterized by a prolonged period of cold in the Northeast and a mild winter on the West Coast. ?
Seems more and more that is just always the case. They never seem to have to deal with strongly negative temp anomalies in winter, while we get hammered in the East. Their drought will only get worse the more mild winters they get while we get clobbered.
I'm so sick of us on the East Coast getting hit year after year, and the West Coast always seems mild. When are they going to take a hit and give us a break in the East?
A bit late, but here's the answer to your question. You could probably look up the details yourself, but hopefully this post might further discussion for those unfamiliar with El Niño. El Niño is a change in the sea temperatures of the equatorial Pacific. The usual pattern is:
1) Trade winds blow from east to west
2) These trade wind push the warm surface water towards the western Pacific
3) Western Pacific has much warmer sea surface temperatures than the eastern Pacific
4) The warmth of the western Pacific waters extend very deep below the surface, meanwhile on the eastern side cooler deep water rises or upwells to the surface to replace the surface waters pushed to the west.
So there's a large chunk of very warm water sitting behind the surface of the western Pacific, while the surface of the eastern Pacific is relatively cool (22°C or so cool for the tropics). The air above hotter water tends to rise, producing low pressure and precipitation in areas near the western Pacific Ocean. Conversely, the eastern Pacific side tends to be relatively dry with sinking air. In El Niño the pattern reverses
1) Trade winds weaken or even reverse
2) Warmer surface waters are no longer pushed westwards by trade winds
3) A wave in the deeper ocean sends of the warm water in the subsurface western Pacific eastward
Now, the eastern Pacific waters are much warmer. The low and high pressure systems shift, areas facing the western Pacific (such as Australia and Indonesia) get much drier while the eastern Pacific gets wetter. In the midllatitude winter, the jet stream or its subtropical branch (called the "subtropical jet") gets stronger. From I've read, this is caused by the Hadley Cell getting stronger. The Hadley Cell is a circulation zone in the tropics/subtropics (from about the equator to 30°), warm, moist air rises on the equator side sinks on the poleward side. The subtropical jet forms on the poleward side of the Hadley Cell. The stronger subtropical jets means a more consistent prevailing weather flow from west to east. The southern US, this means wetter and milder in the winter.
A strong El Niño influence weather globally by rearranging the usual atmospheric circulation, other weather oscillations aren't as strong. And while El Niño can't create heat, by moving heat from below the surface of the ocean to the surface it increases the average sea surface temperatures of the ocean. Oceans hold a lot of heat; that warm water heats and moistens the atmosphere above, increasing the overall average temperature of the earth during the duration of the El Niño. So, El Niño years are warmer than otherwise.
As for attention, the last El Niño of similar size was 1997-98, earlier than that 1982-83. It doesn't happen that often, and it has a big impact on weather globally. And there's additional interest in California, as the strengthened subtropical jet should mean a wet winter there — very wanted after a long drought. My explanation might be incomplete but hopefully it gives a general idea.
A bit late, but here's the answer to your question. You could probably look up the details yourself, but hopefully this post might further discussion for those unfamiliar with El Niño. El Niño is a change in the sea temperatures of the equatorial Pacific. The usual pattern is:
1) Trade winds blow from east to west
2) These trade wind push the warm surface water towards the western Pacific
3) Western Pacific has much warmer sea surface temperatures than the eastern Pacific
4) The warmth of the western Pacific waters extend very deep below the surface, meanwhile on the eastern side cooler deep water rises or upwells to the surface to replace the surface waters pushed to the west.
So there's a large chunk of very warm water sitting behind the surface of the western Pacific, while the surface of the eastern Pacific is relatively cool (22°C or so cool for the tropics). The air above hotter water tends to rise, producing low pressure and precipitation in areas near the western Pacific Ocean. Conversely, the eastern Pacific side tends to be relatively dry with sinking air. In El Niño the pattern reverses
1) Trade winds weaken or even reverse
2) Warmer surface waters are no longer pushed westwards by trade winds
3) A wave in the deeper ocean sends of the warm water in the subsurface western Pacific eastward
Now, the eastern Pacific waters are much warmer. The low and high pressure systems shift, areas facing the western Pacific (such as Australia and Indonesia) get much drier while the eastern Pacific gets wetter. In the midllatitude winter, the jet stream or its subtropical branch (called the "subtropical jet") gets stronger. From I've read, this is caused by the Hadley Cell getting stronger. The Hadley Cell is a circulation zone in the tropics/subtropics (from about the equator to 30°), warm, moist air rises on the equator side sinks on the poleward side. The subtropical jet forms on the poleward side of the Hadley Cell. The stronger subtropical jets means a more consistent prevailing weather flow from west to east. The southern US, this means wetter and milder in the winter.
A strong El Niño influence weather globally by rearranging the usual atmospheric circulation, other weather oscillations aren't as strong. And while El Niño can't create heat, by moving heat from below the surface of the ocean to the surface it increases the average sea surface temperatures of the ocean. Oceans hold a lot of heat; that warm water heats and moistens the atmosphere above, increasing the overall average temperature of the earth during the duration of the El Niño. So, El Niño years are warmer than otherwise.
As for attention, the last El Niño of similar size was 1997-98, earlier than that 1982-83. It doesn't happen that often, and it has a big impact on weather globally. And there's additional interest in California, as the strengthened subtropical jet should mean a wet winter there — very wanted after a long drought. My explanation might be incomplete but hopefully it gives a general idea.
This is a very good write up on El Nino. Thank You.
Thanks. Here's a good webpage that says some of the things I was but with figures. Go up to slide 15 or so, the rest of the slides is part of a more technical presentation on monitioring El Niño by sea level changes using satellite data. Ancient, from 1998. 90s internet!
Comparison of sea surface temperatures this October with October of the last big El Niño (1997). The eastern Pacific isn't as warm as the 97 one, but there's a lot of warm water in other spots.
All that warm water in the North Pacific has led to discussion the effects of El Niño on the western US won't be the same as usual. The warm water could mean the storms pulled in by the subtropical jet going over the warm water would be moister, leading to more rain over California. Or it could mean high pressure in the area deflecting storms. I think the former will be correct, the effects of El Niño should be strong enough to swamp over the pressure changes in the Pacific. The hot spot further north in the Pacific "the blob" is starting to disappear and the permanent ridge (deflecting storms that would otherwise hit the west coast) we've seen in the west previously winters isn't stuck over there anymore.
This El Niño compared to previous ones. The only two that were bigger were the 82/83 and 97/98 ones. This ones not over yet, so it could get a bit stronger. The El Niños in the 50s to 70s except for maybe the mid 70s one weren't that strong, so their influence wasn't that obvious globally (still important if you lived in say, Peru) but just one influence out of many more in most of the world.
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