Heatwave & Tropical night
Summer 2024: Record-High Temperatures Driven by Complex Weather Factors
1. Causes of the Heatwave
Heatwave
A heatwave is a natural disaster characterized by abnormally high temperatures lasting from several days to weeks, causing harm to both lives and property.
Causes of the Heatwave
Heatwaves occur due to a combination of various meteorological and climatic factors. The main causes are as follows:
Climate Change
It is the fundamental background of heatwaves.
As global warming raises average summer temperatures, heatwaves are becoming more intense.
Climate experts predict that by the end of the 21st century, the global average temperature could rise by 1.8°C to as much as 6.4°C.
Rising Sea Surface Temperatures in the North Atlantic & Influence of the Tibetan High
High-pressure systems form, concentrating solar radiation in the affected area.
El Niño Phenomenon
The amount of water vapor in the atmosphere increases, leading to higher perceived temperatures (heat index).
Stagnation of the North Pacific High
In summer, when the North Pacific High settles over the Korean Peninsula and remains stationary for an extended period, it generates descending air currents.
These suppress cloud formation, allowing solar radiation to reach the surface directly, which rapidly increases ground temperatures.
Weak Winds Under High-Pressure Systems
Under high-pressure systems, winds weaken and atmospheric stagnation occurs, causing hot air to remain in place. This creates a vicious cycle where accumulated heat cannot dissipate, and solar radiation continues to build up at the surface.
Inhibition of Nighttime Radiative Cooling Due to Greenhouse Gases
During the day, the heated surface emits heat in the form of infrared radiation, but this heat is reabsorbed by greenhouse gases such as carbon dioxide and water vapor.
As a result, the surface does not cool sufficiently at night, leading to the occurrence of tropical nights.
Heat Dome Phenomenon
A heat dome is a phenomenon where a strong high-pressure system forms a dome-shaped thermal barrier, trapping hot air near the surface.
It occurs due to the coupling of multiple high-pressure systems.
Urban Heat Island (UHI) Effect
During the day, the heated ground emits heat in the form of infrared radiation. However, this heat is reabsorbed by greenhouse gases such as carbon dioxide and water vapor.
As a result, the surface does not cool sufficiently at night, leading to the occurrence of tropical nights.
* Heat Dome Phenomenon
A phenomenon in which a strong high-pressure system forms a dome-shaped heat barrier, trapping hot air near the ground.
1. Conditions for Formation
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Clear, cloudless skies
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Intense solar radiation at the surface
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Blocked air circulation → Rapid temperature rise
2. Korean Peninsula Case
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Northward expansion of the North Pacific High (oceanic) + Southward movement of the Tibetan High (continental)
→ Formation of high-pressure coupling → Dome-shaped atmospheric cover
3. Meteorological Mechanism
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Descending air under high pressure → Compression and heating of air
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Concentrated solar radiation + Suppressed emission of surface heat → Heat accumulation
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Weakening of jet stream → Prolonged stagnation of high pressure → Persistent heatwave
2. Tropical Night
Tropical Night
A hot night when the minimum temperature stays above 25°C.
It occurs when the daytime heat extends into the night without sufficient cooling.
Causes of Tropical Nights
Expansion of the North Pacific High
As the North Pacific High expands, hot and humid air flows into the Korean Peninsula. When humidity levels rise, the radiative cooling effect weakens significantly at night, preventing surface temperatures from dropping.
As a result, high temperatures persist through the night, leading to the occurrence of tropical nights.
Urban Heat Island Effect
Urban areas accumulate a large amount of heat during the day due to surfaces like asphalt and concrete. At night, this heat is released slowly, preventing temperatures from dropping sufficiently.
Additionally, structural issues such as artificial heat sources, reduced ventilation, and a lack of green spaces further inhibit radiative cooling, increasing the likelihood of tropical nights.