After a week of extreme heat reaching nearly 40 degrees Celsius, from the night of the 3rd, extreme heavy rain with hourly precipitation exceeding 140 mm began pouring down starting in the South Jeolla Province, then spreading to the Gyeongsang region and North Chungcheong Province. The Korea Meteorological Administration forecasted that heavy rain would continue in the metropolitan area this week.
Experts suspect that the severe heavy rain following the heat wave was due to moisture added by the vapor left behind as a powerful high pressure system formed over the Korean Peninsula and the typhoon dissipated. However, some argued that it may only be after this summer ends that the precise analysis of the connection between the heat wave and the heavy rain can be conducted.
On the 4th, Professor Kim Baek-min from Pukyong National University's Department of Environmental Atmospheric Sciences cited the extremely strong high pressure system as a reason the pattern of heat wave followed by heavy rain occurs frequently. He noted, "The North Pacific high pressure system, which has been strongly formed due to global warming, has expanded, causing sea temperatures to rise," adding, "In particular, the sea surface temperature in the southern waters of the Korean Peninsula has risen sharply."
The North Pacific high pressure system is a hot and humid subtropical high that significantly influences the weather in Korea during the summer. Originating from the North Pacific, it affects the Korean Peninsula while causing hot weather due to high temperatures and southwest or southeast seasonal winds.
Professor Kim Baek-min said, "The reason heavy rain pours down after a heat wave in Korea is due to rising sea temperatures," explaining that when the North Pacific high pressure system expands, cold and dry air from the north descends and collides strongly with the high pressure, resulting in heavy rain.
Professor Kim compared this summer to the hottest summers of 1994 and 2008. He explained, "When we look at times of severe heat waves in Korea, we can see that in addition to the North Pacific high pressure, a Tibetan high pressure system forms to the west," noting, "The presence of these two high-pressure systems covering the Korean Peninsula tends to maintain their strength more forcefully, leading to more severe heat waves."
In particular, Professor Kim noted, "The extreme heavy rain that fell last weekend was also influenced by the remnants left behind when Typhoon No. 8, 'Kkomai,' dissipated." He stated that the tropical moisture left behind as Kkomai dissipated over China was carried to the Korean Peninsula by southern winds and fell as a deluge.
When a powerful high pressure system forms, it usually influences the path of typhoons. Professor Kim explained, "The high pressure acts as a sort of barrier, preventing the typhoon from proceeding," but added, "This time, the remnants of the typhoon entered the Korean Peninsula during a moment when the North Pacific high pressure weakened briefly."
Some believe that the phenomenon of intense rain falling in a short period during a heat wave, known as a squall, has appeared in Korea as well. A squall often occurs when the surface is heated up extremely high in tropical regions, causing atmospheric instability and resulting in sudden showers. It generally appears in the afternoon when the humidity is high and strong sunlight is present.
However, Woojin Kyu, a spokesperson for the Korea Meteorological Administration, stated, "A squall is a phenomenon where strong rain falls temporarily, so it is limited to describe the prolonged heavy rains following a heat wave in Korea as merely a squall."
Some opinions also indicated that it will be necessary to wait until summer is over to accurately ascertain whether this summer's heat wave-heavy rain pattern is truly a reality and what its causes are.
Woojin Kyu noted, "To understand what changes are happening on Earth and to analyze the heavy rain-heat wave pattern from a climatic perspective, it is difficult to rely solely on data from a few weeks," adding, "It requires analyzing several months to over a year of data." He stated, "Since summer still has a long way to go, we will be able to analyze the causes after observing trends for another month and compiling statistics."
Recently, there has been a chilling joke circulating on social networks (SNS) suggesting that "this summer will be the coolest summer yet." Professor Kim Baek-min asserted, "Extreme heat waves like this year may become commonplace in the future," while also stating, "We need to prepare for extreme heat, but it is unlikely that temperatures will continue to rise at this rate, so there is no need for excessive fear."