On the EL NIÑO/SOUTHERN OSCILLATION (ENSO) page of the U.S. Oceanic and Atmospheric Administration, the outlook for la Niña is continuous:
- The probability for the period from June to August 2022 is 59%;
- The probability of outlook for the entire fall of 2022 is 50-55%;
On the page of the Japan Meteorological Agency, the outlook for la Niña is more "radical".
- Patterns in the atmosphere and oceans suggest that la Niña in the equatorial Pacific ocean continues;
- La Niña is more likely to persist (60%) until the end of the northern spring than not to continue (40%);
- During the northern summer, la Niña phenomenon is more likely to shift to ENSO neutral (70%);
I believe that you should have a deep memory of the cold winter of La Niña in 2020, the La Niña phenomenon that began in the summer and autumn of 2020 lasted until 2021, the summer had a brief change to neutral, the autumn began to be La Niña, everyone continued to live a La Niña winter, to the spring and summer of 2022, La Niña is still continuing, how will the climate change in 2022?
How much does La Niña really have to do with climate?
La Niña is a very complex weather pattern, and although the deep causes have diverged so far, it is recognized that the water temperature in the equatorial Pacific region changes abnormally:
In November 2007, the sea surface temperature was abnormal, indicating la Niña phenomenon
During la Niña, the sea surface temperature in the eastern equator of the Central Pacific Ocean will be 3-5 °C lower than normal (the general temperature difference is more than 0.5 °C for more than 6 months, then the La Niña phenomenon can be considered to have occurred), it will last for at least 5 months, that is, autumn, then it will continue to last until the following spring.
It has a wide impact on global weather, even affecting the Atlantic and Pacific hurricane seasons, where more tropical cyclones occur in the Atlantic Ocean due to low wind shear and rising sea surface temperatures, while reducing the formation of tropical cyclones in the Pacific.
The La Niña phenomenon and the southern oscillation
When seeing La Niña, you usually see SOUTHERN OSCILLATION (ENSO) at the same time, because there is a correlation between these phenomena, and the southern oscillation itself refers to the sea surface temperature in the equatorial region of the eastern Pacific Ocean (warming during el Niño events, cooling during la Niña events) and changes in sea surface pressure in the equatorial region of the western Pacific Ocean:
The warm ocean phase of the eastern Pacific, known as El Niño, is accompanied by high air pressure on the surface of the western Pacific;
The cooling phase of the eastern Pacific, la Niña, is accompanied by low air pressure on the sea surface in the western Pacific;
As mentioned above, La Niña and El Niño are just the opposite, La Niña is the west side of the central Pacific ocean is warm, while El Niño is the east side of the central Pacific Ocean is warmer:
The driving force behind this imagination is the Walker Circulation over the equatorial Pacific Ocean, a large-scale circulation formed by warm water vapor and the rotation of the Earth.
Normal year Walker circulation
La Niña Vintage Walker Circulation
El Niño Year Walker Circulation
La Niña and climate change
La Niña phenomenon enhances the temperature of the sea level in the western Pacific Ocean, will enhance the water vapor cycle closely related to the climate, it will definitely change the regional climate, summer is coming, affecting the continent's climate is mainly three: plum rain, summer floods and typhoons, so how does the La Niña phenomenon change the continent's summer and autumn climate?
Rainy Season: What's the Rainy Trend?
Plum rain is a slow-moving rainfall zone formed from south to north in the south of the continent under the squeeze of the western Pacific subtropical high-pressure zone, which forms a slow-moving rainfall belt from south to north in the south of the continent with the cold air flowing northward with the southwest monsoon in the southwest, and the cold air retreating northward in the north direction, which depends on three factors:
- Northern cold air strength;
- Southwest monsoon strength;
- Strength of the subtropical high-pressure zone;
Is the cold air in the north strong or weak?
The strength of the cold air in the north is related to the Arctic vortex (there are also eddies in the south pole), which is a continuous and large-scale cyclone born in the polar region, between the middle and upper stratospheres of the troposphere and the stratosphere. The Arctic is heavily mountainous, and the Rosbi wave causes the vortex to rupture, and there are two centers of the Arctic vortex, one over Siberia and the other over the Canadian island of Baffin.
Divided Arctic vortex
The strength of the Arctic vortex is also related to the Polar Oscillation (the South Pole also has oscillations), when the North Pole oscillates, the Arctic Vortex intersects with the warm and humid air flow in the mid-latitudes to form a relatively normal weather, but when the Negative Arctic Oscillation causes extreme cold winters, such as during the Negative Arctic Oscillation in 2010, two major blizzards in Western Europe, icy weather and cold temperatures have caused serious damage in most parts of the region.
On April 7, 2022, air with a higher temperature than normal year was located in the uppermost part of the atmosphere
The above figure shows that the temperature of the Upper Arctic atmosphere is higher than in previous years, which means that the Arctic vortex may rupture and dissipate earlier, reducing the impact of Arctic oscillations on the climate of the lower latitudes, that is, cold air may be weak in the rainy season, but the problem remains, affecting the continental climate only requires local cold currents, even if the ruptured Arctic vortex can also cause the continent's cold air to strengthen in a certain period of time.
What exactly is the southwest monsoon like?
The strength of the southwest monsoon depends on the Indian Ocean dipole phenomenon, which is somewhat similar to the La Niña phenomenon, when the positive dipole occurs, the sea surface temperature on the west side of the Indian Ocean continues to warm abnormally, so that east Africa will produce greater rainfall, the east side will reduce the water temperature, the water vapor will decrease, the southwest monsoon is weak, and vice versa.
However, due to the relatively small size of the Indian Ocean, it does not last that long, usually starting around May and June, peaking between August and October, and then decaying rapidly when the monsoon reaches the southern hemisphere at the end of spring. Overlapping with the rainy season in the mainland, the interval between the end of May and the end of June, the initial impact of development is not large.
Is the subtropical high-pressure zone strong?
One thing is certain, La Niña weakens the subtropical high pressure zone, because the subtropical high pressure zone is a descending high pressure, and the water temperature too high in the west will form an updraft and weaken this subtropical high pressure.
The vice-high is weak, the northern cold air invades the south, the southwest monsoon does not have a sub-high squeeze, it may stay in the south for a long time, the result should be an increase in rainy days in the south, but the cold air in the north is uncertain, if the cold air is weak, then the rain belt should be north, and the rainy season time in the south will be shortened.
At least the rainy season is really unpredictable, and there is still considerable uncertainty.
What will the weather look like this summer?
The impact of la Niña on the summer climate is more complex, because this is when the temperature of the Ocean in the West Pacific gradually increases, and the temperature rise caused by La Niña will be relatively weakened from the Eastern Pacific, so most of the la Niña summer is relatively neutral, but there will still be an impact, such as 1998, which is a special year by a strong El Niño phenomenon but within a month to lanina:
Around June 1998, summer has arrived, the rain belt has moved north, the flood season in the Yangtze River Basin should end, La Niña appeared within a month, the air in the south became cold and sinking, and the warm and humid currents that had moved north were returned to fill in, resulting in frequent rainfall in Jiangnan and South China, serious floods in the Yangtze River Basin and the two lake basins, the water level of some rivers exceeded the alert water level for a long time, the rainfall in parts of Liangguang and Yunnan was also more than 50%, and there were also waterlogging in parts of North China and Northeast China (98 flood rescue).
At that time, Vice Gao had reached 30 degrees north latitude on July 10, but then suddenly retreated south to 18 degrees north latitude, chao Jiping, academician of the Chinese Academy of Sciences and honorary director of the National Marine Environment Forecasting and Research Center, said that he had never seen such a strange phenomenon in history.
1998 is a year in which a strong El Niño phenomenon was transformed into a La Niña, which may not be of much reference, but 2008 is a medium-intensity Year of La Niña, which is somewhat similar to this year's situation, and can be compared with some references:
The above figure is the distribution of water temperature in the west and east pacific waters of the equatorial Pacific Ocean from March to April 2008, the maximum difference is about 1 °C, although it is still in the range of La Niña phenomenon, but it is already relatively low, so what about the continental summer in 2008?
- In January 2008, the mainland suffered a rare snow disaster, which is estimated to be remembered by everyone, but it is not among the summer weather discussed in this article, and since the spring of 2008, the average continental temperature has been 1.8 °C higher than the same period in previous years, and 0.6 °C higher than that of 2007 rice cake.
- By the end of July, heavy rain to heavy rain fell in Huanghuai, Jianghuai, Jianghan and other places in the Sichuan Basin, with rainfall reaching 100 to 180 mm, and heavy rain and flood disasters occurred in parts of Hubei, Sichuan, Jiangsu, Shandong, Anhui and Chongqing.
- At the end of August, Shanghai experienced the strongest rainstorm weather after the flood, and the maximum precipitation in Xuhui District was 117.5 mm in one hour, which was unprecedented since meteorological records were recorded in 1872.
Since the beginning of summer, the north has begun to have a relatively large-scale drought, and by late October, Henan Province has had no effective rainfall for more than 100 consecutive days, and the drought-stricken area of the province has reached 63.1%, suffering from extreme drought since 1951.
Basically in line with the state of the south flood and the northern drought La Niña year, and in 2021 the La Niña year is somewhat different, originally last year was relatively close, but also more reference significance, but last year's June-August is a neutral year, it is not much to introduce.
Are there more or fewer typhoons this year?
The answer is that the probability will increase! Because La Niña will raise the water temperature in the lower latitudes of the Western Pacific, which is the "old nest" of typhoons, the generation of typhoons in the Western Pacific will increase in the La Niña year, and another problem is that the vice-high of the La Niña year will be further north, blocking the typhoon's way to the Pacific Ocean and Japan's eastward progress!
The country's coastline facing the Pacific Ocean is the longest, so the probability of typhoons making landfall on the continent will also increase, which is not good news, because typhoon data since 1949 show this:
- From 1949 to 1996, the annual average number of typhoons generated in the northwest Pacific Ocean and the South China Sea was 28, and the average number of typhoons that made landfall on the mainland was 7.
- The average number of El Niño typhoons generated 26.4 and the average number of landfalls was 6.2, and the number of years with normal or low number of generations and landings accounted for 67% and 80% of the number of El Niño years, respectively.
- The average number of typhoons generated in La Niña is 31.3 and 8 are landfalls, accounting for 73% and 64% of the annual number of la Niña years, respectively, with normal or partial number of landfalls.
From this point of view, the summer and autumn of 2022 will not make you feel better, and in the summer, everyone should pay attention to when the first typhoon comes, and it is likely that in 2022, there will be an early typhoon in the summer.
What is the current state of La Niña?
At the end of the article, the La Niña phenomenon of the United States Oceanic and Atmospheric Administration and the Japan Meteorological Agency will be given, and there are very detailed icons attached to the text, which you can understand if you are interested.
The above figure has been a continuous GIF of the water temperature change in the Equatorial Pacific since January 2022, and it can also be seen in this picture that the "hot water" is really blown into the Western Pacific, while the cold water below the Eastern Pacific is flooded, and the average temperature is about 0.7 °C lower than that of the Eastern Pacific, and the standard of La Niña is higher than 0.5 °C, so it is still in the State of La Niña.
The above figure is more in line with everyone's viewing habits, the gray area on the left is China, the lower left is Australia, and the gray on the right is the Americas region, which is more intuitive. According to the latest CPC/IRI projections, there is a 59% chance that the La Niña phenomenon will last until the winter in the Southern Hemisphere, and a 50% to 55% chance of continuing into the spring in the Southern Hemisphere, which means that it will continue until this year's winter (Northern Hemisphere winter).
Long-wave radiation emitted in March 2022 compared to the 1991-2020 average
For the third consecutive year, it has basically reached the highest record of three consecutive years in the La Niña year! So what exactly is this La Niña phenomenon trying to do?
In fact, the answer is not too worried, La Niña is just a climatic phenomenon, it has no purpose! However, we should be more worried about the increase in extreme weather, because as the global temperature rises, a large amount of water vapor enters the atmosphere, these increased water vapor carries a lot of energy, there needs to be a catharsis, extreme rainstorms, droughts and typhoons and more fires may occur, you should be careful that it is extreme weather.
reference:
https://www.cpc.ncep.noaa.gov/products/analysis_monitoring/enso_advisory/ensodisc.shtml
https://ds.data.jma.go.jp/tcc/tcc/products/elnino/outlook.html
https://www.weatherzone.com.au/news/la-nina-holding-on-in-pacific-ocean-but-for-how-long/537153
http://zwgk.cma.gov.cn/kppd/kppdqxwq/kppdjckp/201212/t20121217_197508.html