The blizzard continues.

There is hope that it will slow down as there is a rain forecast this weekend, but it seems that it will not be enough to beat the heat.

Even if the temperature is slightly lower than during the week, the humidity is high and the perceived temperature is highly likely to exceed the heat wave standard.

The average high temperature in July in Seoul was 32 degrees, the second highest on record after 1994.

On the 29th, the Korea Meteorological Administration predicted that the daytime high of 34 degrees and the low of 26 degrees in Seoul will continue in the first week of August.

When the minimum temperature exceeds 26 degrees Celsius, it means not only that it is hot during the day, but that the tropical night continues.



[What is that?] How hot does it have to be for a 'heat wave'?

How hot do you use the word 'heat wave'? The Korea Meteorological Administration issues a heat wave advisory if the sensible temperature of 33°C or higher lasts for more than two days from May to September. If the sensible temperature rises further and it stays above 35℃ for more than 2 days, a heat wave 'alarm' is issued. According to the government meteorological data open portal, the number of heatwave days in July this year in Seoul and Gyeonggi was 11.8 days, whereas in July last year, when the rainy season was long, the number of heatwave days was only 0.2. It is natural to feel that it is much hotter than last year (the number of heatwave days in July 2018, which was recorded as an all-time heatwave, was 13.3 days).



It is not only hot in Korea. Europe and the United States are already suffering from heatwaves exceeding 40-50 degrees Celsius since last June, to the extent that the World Meteorological Organization describes it as an 'extreme summer'. Some media also introduced social media photos of tires, traffic lights, and plastic trash cans melted in the heat in these countries (the photos in question are below.... Facebook capture).





As a result of fact-checking by media outlets from around the world, it was revealed that these photos were not due to a heat wave, but because the car was driven on asphalt or melted in a fire. .



The mid-latitude region has historically experienced relatively little extreme climate change, and is a region where countries where people can live and live have developed.

But, why does it rain here?

Global warming has had a major impact.

As the Arctic temperature has risen recently, the temperature difference between the equator and the equator has narrowed and the jet stream has weakened.

The weakening of the jet stream causes polar air to flow from places to lower latitudes, obstructing east-west airflow.

High pressures created throughout the mid-latitude regions stagnate and heat build-up.

A typical example of this is the heat wave that caused large-scale wildfires in North America.



[WHY?] How is this year's heatwave different from the heatwave in 2018?

In Korea this year, additional regional factors are at work.

First, the rainy season ended early and with less energy.

This year, the rainy season front caused great damage to the Jeollanam-do region, but relatively little rain was applied to the rest of the region.

According to the Korea Meteorological Administration, this year's rainy season ended from July 3 to 19, the third shortest period in history.

The rainy season front gave up the Korean peninsula to the North Pacific high pressure without enough rain to cool it down.

Hot air also came from inland areas such as northern China and Mongolia.



The 'heat dome' phenomenon occurs when the heat, which is generally called a heat wave, makes people hard in the summer.

A thermal dome refers to a state in which hot air is covering a certain area like a round dome roof of a building, so that the heat does not escape and stagnates.





The summer of 2018 was typically such a case.

At that time, the North Pacific high pressure developed strongly and covered the Korean Peninsula, and the Tibetan high pressure in the western inland of Asia also expanded over the Korean Peninsula.





The North Pacific high pressure, filled with the moisture of the hot sea, was located on the land of Korea, and on top of that, the Tibetan high pressure containing the hot air from the inland was piled up to form a ten dome.



So this year?

July of this year was also very hot, but many people felt that it wasn't as bad as in 2018.

There is a reason.

In early to mid-July this year, the North Pacific high pressure developed in the form of a shorter north-south length and a longer east-west direction.

It was different from the one that covered Taiwan, the eastern coast of China, and all of Japan during the great heatwave in 2018 (it's a little different now, at the end of the month).





Meanwhile, the Tibetan high pressure, which supplies hot and dry air from the inland west of China, was originally predicted to cover the Korean Peninsula as in 2018, but in reality it did not grow to the Korean Peninsula.

Instead, it indirectly affected the heat of the Korean Peninsula through the airspace over northern China and Mongolia.

Myung-in Lee, director of the Center for Heatwave Special Meteorology Research Center at Ulsan Institute of Science and Technology, predicted on the 27th that this heatwave would not be as fierce as the heatwave in 2018. I heard the point.


Why was it less sticky for a heatwave?

In general, the heatwave in July was not as humid as the heatwave in 2018.

This is related to the pattern of the North Pacific high pressure described above.

Since the North Pacific high pressure is a mass of air that is large and strong enough to repel any typhoon, the wind stream coming to the Korean Peninsula flows along the boundary of the North Pacific high pressure.

In 2018, the North Pacific high pressure was so large and strong that the winds coming into the Korean Peninsula brought in a lot of hot and humid air from Southeast Asia and the South China Sea (the figure below shows a comparison between 2018 and 2021 if you wait a little bit).





On the other hand, during July of this year, the North Pacific high pressure was elongated from east to west and short from north to south, so the winds tended to come in from the southeast toward the east coast of Korea.



The water temperature in the eastern sea of ​​Korea is colder than that of Southeast Asia.

So this wind holds less water vapor (the air can hold more moisture at higher temperatures).

In the central part of the country, a phenomenon was also observed.





It is a phenomenon in which the wind blowing from the east coast passes over a mountain range over 1,000 meters above sea level, condensing it into raindrops and dropping it, and as it descends to the west, it turns into a hot and dry wind.



Thanks to this, in July of this year, there were many days that were not like a wet sauna even though it was a heat wave, and were closer to 'baking heat' than 'steaming heat'.

In late July of normal years, the humidity soared to 80-90%, and it was common for people to complain, 'If that's the case, it's better to pour it down with rain'.

This year, there were many days when the midday humidity was in the 50-60% range.

The figure below compares the sensible temperature on July 24, 2018 and on the same day this year (red is over 35 degrees, green is below 30 degrees).





However, since the second half of this week, the pattern of high pressure in the North Pacific has changed again, and hot and humid winds from the southwest have increased.

As a result, rain is forecast for the weekend in some areas.

It seems to be changing to a 'wet heat wave' that is somewhat different from the pattern seen this month.

The weather is always changeable, and it doesn't move as people expect it to.


[Don't be vigilant] Heat illness...

can be life threatening

Even if it's not as hot as in 2018, it's hot.

On the 30th, ahead of the weekend, the Korea Meteorological Administration lowered the heat wave warning for the metropolitan area from a warning to a warning, but the heat wave is the same.

The heat wave continues to cause people to collapse and even lose their lives.

According to statistics from the Korea Centers for Disease Control and Prevention, between May 20 and July 29, 910 people were admitted to the emergency room due to heat illness, and 12 of them died.

For workers who have to continue working in hot places or energy-poor people living in poor air-conditioning environments, heat is a life-threatening risk factor.




(Picture = Captured from the website of the Ministry of Environment) It



is important how severe weather phenomena such as heat, rain, and cold are, but how long they last has a big impact on people.



So when will this storm end?

As the forecast was introduced at the beginning of the article, it is highly likely that the current heat wave will continue until at least the beginning of August. Statistically, after the second week of August in Korea, the influence of the North Pacific high pressure gradually weakens and the tropical cyclone moves northward and the scorching heat is fading. It means that people's rule of thumb, 'After Liberation Day, it becomes a little more affordable', will not be too wrong this year.



There was no typhoon that directly affected the Korean Peninsula in July of this year. In July of the previous year, it was different from the one that had an effect. So what about August-September? There is no correlation between the number of typhoons coming to the Korean Peninsula in July and the number of typhoons coming in August-September. This is even more so due to the wide range of weather fluctuations due to global warming. Even if a typhoon comes, I just hope that it will cool the heat without causing any damage.



(Composition: Senior Correspondent Lee Hyun-sik, Reporter Jang Seon-i, Editor Kim Hwi-ran / Designer: Myung Ha-eun, Lee Ji-soo / Advisor: Jung Gu-hee, SBS Weather Reporter)