What is the El Nino phenomenon?
October 14, 14:38
"It's cold today" or "it's starting to rain", we live every day feeling the small changes in the weather.
This time, it is an entrance examination question about a slightly longer-term meteorological phenomenon.
Challenge the problem!
Problem
(1) What do you call the phenomenon that the water temperature near the sea surface off Peru rises abnormally for about a year?
(Senzoku Gakuen Junior High School 2020)
The correct answer is "El Nino phenomenon".
Off the coast of South America, it often happens that the water temperature near the sea surface rises around Christmas time.
This is the origin of the name, which is locally called "El Nino, Son of God" after Christ in Spanish.
The problem continues.
Problem
(2) What is the tendency of this phenomenon in Japan compared to normal years?
Select the most appropriate one from the following and answer with a symbol.
A. The temperature is low in both summer and winter.
B. The temperature is low in summer and high in winter.
C. The temperature is high in summer and low in winter.
D. The temperature is high in both summer and winter.
(Senzoku Gakuen Junior High School 2020)
It's a little difficult.
The correct answer is a, "The temperature is low in summer and high in winter."
Why is it a cold summer / warm winter when the El Nino phenomenon occurs?
Mechanism of the El Nino phenomenon
Mr. Hiroshi Nakamikawa of the Climate Information Division of the Japan Meteorological Agency taught me.
Let's check from the mechanism of the El Nino phenomenon.
Mr. Nakamikawa
"Under normal conditions, the easterly wind, which is said to be a trade wind, is almost always blowing on the equator."
The point is near the equator of the Pacific Ocean.
It is a view of it in cross section from the south side.
First, in normal times.
The wind that blows from east to west causes warm seawater near the surface of the sea to flow to the west and gather.
And here is when the El Nino phenomenon is happening.
If the easterly wind weakens for some reason, warm seawater will not be blown.
Warm water does not collect on the west side, and the sea surface temperature drops below normal.
Looking at this state from the sky, it looks like this.
Near the equator on the west side of the Pacific Ocean, the sea surface temperature drops, making cumulonimbus clouds less likely to form.
The difficulty of forming cumulonimbus clouds affects the flow of air around them.
For example, summer.
The "Pacific High" often heard in the weather forecast.
When this is normal, it overhangs north enough to cover Japan ...
This overhang weakens when cumulonimbus clouds are less likely to form due to the El Nino phenomenon.
In other words, Japan is less likely to be covered by the Pacific High, so it doesn't get hot.
Mr. Nakamikawa
"I think it's good to think that the strongest position of the high pressure shifts. The mechanism is that the Pacific high pressure does not become so strong and it tends to be a cold summer tendency."
And winter.
When cumulonimbus clouds are less likely to form, the westerlies that meander from north to south in the sky also change.
The width of the meandering will increase, and in the vicinity of Japan, it will pass further north.
This makes it difficult for cold air from Siberia to flow over the north of Japan, resulting in a mild winter.
When the El Nino phenomenon occurs due to various other factors, it is easy for Japan to have a cold summer or a warm winter.
"Ocean observation" to capture changes
By the way, how do you think you know if the El Nino phenomenon has happened?
Roughly speaking, when the water temperature near the equator off South America has been higher than normal by 0.5 degrees or more for 6 months or more.
This is the El Nino phenomenon.
Isn't it surprising that the weather is affected at just 0.5 degrees?
This is Nara Tax from the Marine Meteorological Division of the Japan Meteorological Agency.
Mr. Nara
"Even a slight difference will affect our weather, climate, and daily life."
An observation device called "Argofloat" captures slight changes in seawater temperature.
Data is sent by measuring temperature and water pressure at various depths while automatically ups and downs.
As an international project, more than 3,900 units are currently in operation in the oceans around the world.
Mr. Nara
"Ocean fluctuations are slow in the long run, but they are causing big fluctuations and have a great impact on us. What will happen in the future generation of children is still the ocean. If you don't know what's inside, you won't be able to respond correctly. I think it's a necessary observation over a long period of time. "
In order to think about the global environment, it is essential to observe seawater widely and deeply.
"Reverse tendency" is the La Nina phenomenon
So far, we have looked at the El Nino phenomenon, but the Japan Meteorological Agency has announced that the opposite, the "La Nina phenomenon," in which winter temperatures tend to be lower, is likely to occur (October 2020). Current).
Mr. Nakamikawa of the Japan Meteorological Agency, who visited this time, said about this winter, "Due to global warming, the temperature of the atmosphere is high, and the effect of the La Nina phenomenon on the temperature may be limited. There are other factors that can affect it, so be prepared for heavy snow and low temperatures. "
In the winter when the La Niña phenomenon occurred in 2017, heavy snowfall occurred in various places.
Stay alert and check the weather information.
In "Migake, Curiosity!" Of "Weekly Maru-Knowledge News" (broadcast at 9:00 am on Saturday), we will delve into the news every week on the subject of current affairs presented in the entrance examination.
Let's think of "why?" And "in the first place" that you really want to know as Kamakura casters!
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https://www3.nhk.or.jp/news/special/maruwaka-migake/