KOR
▲ Heatwave
The Korea Meteorological Administration (KMA) has analyzed that the "extreme heatwave" in Yangsan—which broke the national record again today (the 2nd) by hitting a daytime high of 42.5°C (109°F)—and other inland areas of South Gyeongsang Province is due to a combination of conditions that created the "optimal environment for temperature increases."
First, the KMA pointed to the dual pressure system of the North Pacific high and the Tibetan high blanketing the Korean Peninsula as the primary cause of the heatwave in the inland areas of South Gyeongsang Province.
A hot and humid North Pacific high stagnated in the mid-lower layers of the atmosphere near South Korea, leading to a continuous inflow of hot and humid westerly and west-northwesterly winds along the edge of the high-pressure system in the lower layers.
After the end of the monsoon season, the Tibetan high expanded into the upper atmosphere, adding a "temperature-raising effect within the high-pressure zone."
Air currents descend within high-pressure zones. As air descends in an adiabatic state (isolated from heat exchange with the outside), an increase in pressure reduces the volume of the air mass and increases its density, causing the temperature to rise.
The hot and humid northwesterly winds blowing from the lower layers particularly drove up temperatures in South Gyeongsang Province because they blew in even hotter after crossing mountain ranges such as the Yeongnam Alps.
This phenomenon, known as the föhn effect, occurs when air becomes hot and dry as it crosses a mountain.
As moist air ascends a mountain slope, the temperature drops by 0.5 to 0.6°C for every 100-meter increase in altitude.
As the temperature falls, water vapor in the air condenses and falls to the ground.
When the dried air, having lost its moisture, descends the mountain slope, the temperature rises by about 1.0°C for every 100-meter decrease in altitude.
Consequently, the region where the wind blows after crossing the mountain—the leeward side—experiences hot and dry winds.
Furthermore, because Yangsan is a basin surrounded by mountains such as Mount Gaji, Mount Shinbul, Mount Maebong, Mount Cheonseong, and Mount Geumjeong, the heat once trapped inside could not easily escape.
The eastern region of South Korea also experienced a large amount of solar radiation as clear weather persisted during a season when the sun's altitude is high.
Last month's total solar radiation in Yangsan reached 582.49 MJ/m², which was about 36% higher than the average July solar radiation of 428.7 MJ/m².
The fact that South Gyeongsang Province received little rain during the monsoon season, leaving the ground dry, was another factor that fueled the temperature rise.
Soil moisture data from the agricultural observation station in Jinju, South Gyeongsang Province, near Yangsan, showed it remained at just 26.3% of normal levels.
Yangsan's daily high temperature had exceeded 40°C (104°F) starting on the 29th of last month, and rose to 41.4°C (107°F) on the 31st of last month and 41.6°C (107°F) yesterday, continuously breaking the record for the highest temperature in the 122-year history of modern meteorological observations in South Korea across 97 climate statistics observation points managed by the KMA for two consecutive days.
(Photo: Yonhap News)
※ Please note: This article was translated by AI and may contain errors.
