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The 2024 Heatwave

A Complex Disaster Triggered by Rising Sea Surface Temperatures, High-Pressure Coupling, and Climate Change

The 2024 Heatwave and Tropical Nights

Causes of the 2024 Heatwave and Tropical Nights

In the summer of 2024, the Korean Peninsula experienced record-breaking heatwaves and tropical nights.
This was the result of a combination of complex meteorological factors, including rising sea surface temperatures, the coupling of high-pressure systems, and climate change.

1 ) Climatic Factor
    : End of El Niño →
     Transition to La Niña 

  • A strong El Niño in 2023 dissipated by the spring of 2024, transitioning into La Niña by summer.

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  • As trade winds strengthened, warm surface waters were pushed westward, leading to a rise in sea surface temperatures in the western Pacific.

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  • This triggered active convection, causing upper-level divergence, which in turn led to the northwestward expansion of the North Pacific High.

2) Rising Sea Surface Temperatures

  • In the summer of 2024, the average sea surface temperature reached 23.9℃ — the highest in the past 10 years and 1.1℃ above the average.

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  • The West Sea was particularly warm, with temperatures 2.1℃ higher than usual, becoming a major source of heat inflow.

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  • In August, sea surface temperatures exceeded 28℃, making nighttime cooling difficult and contributing to the occurrence of tropical nights.

3) Coupling of High-Pressure Systems

  • The North Pacific High extended farther north than usual, while the Tibetan High expanded from northwestern India, together forming a dual high-pressure system over the Korean Peninsula.

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  • This pushed the upper-level jet stream northward, resulting in prolonged clear skies, accumulation of radiative heat, and rising surface temperatures.

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  • This structure can be interpreted as a “heat dome” phenomenon.

4) Southwesterly Winds and Moisture Inflow

  • Along the edges of the North Pacific High, hot and humid southwesterly winds continuously flowed into the region.

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  • A large amount of water vapor was carried into the Korean Peninsula by the southwesterly winds, supplying moisture to the stationary front—resulting in increased rainfall and intensifying tropical nights.

5) Weather Characteristics During Monsoon and Typhoon Seasons

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  • Late June to Mid-July: A combination of meteorological factors brought heavy rainfall, high temperatures, and tropical nights.

During this period, sea surface temperatures in the tropical western Pacific were higher than average, leading to intensified convective activity. The rising air then descended over the subtropical region near Taiwan, causing the North Pacific High to expand farther northwest than usual.

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Along the edges of this high-pressure system, southwesterly winds frequently blew, continuously bringing hot and humid air into Korea—becoming a major driver of rising temperatures.

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Especially in western Korea, stagnant moisture was funneled narrowly along the edge of the high, feeding the stationary front and resulting in frequent, brief but intense localized downpours.

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However, even during rainfall, the continued inflow of warm and humid air at night prevented temperatures from dropping, leading to frequent occurrences of tropical nights.

  • Late July to Late August: Low Precipitation and Possibility of a Heat Dome Due to High-Pressure Coupling

Later, convective activity intensified over the northwestern Pacific due to typhoons, causing the North Pacific High to extend further north. At the same time, increased convection over northwestern India led to the development of the Tibetan High, which expanded northeastward toward the Korean Peninsula.

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As a result, two high-pressure systems settled simultaneously over the region, and the upper-level jet stream was pushed further north.

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This pressure configuration trapped hot, stagnant air over the Korean Peninsula, forming a heat dome. With reduced rainfall and continuous accumulation of solar radiation during the day, the intense heat persisted.

  • Late August: Impact of Typhoons Jongdari and Sanba

As Typhoons Jongdari and Sanba passed near the Korean Peninsula, they brought a large influx of hot and humid air, prolonging heatwaves and tropical nights into late summer.
Rather than causing direct damage, the typhoons contributed by intensifying the thermal conditions.

  • September: Prolonged Late-Summer Heatwave and Tropical Nights Due to Dual High-Pressure Systems

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In the lower atmosphere, moisture continuously flowed in from the south along the edge of the North Pacific High, maintaining hot and humid conditions. As a result, tropical nights persisted through mid-September.

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From early to mid-September, convective activity intensified over the northern Indian Ocean and near the Philippines, further strengthening the Tibetan High and the North Pacific High, respectively.

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Although a period of heavy rainfall occurred in September, which temporarily weakened the upper-level high-pressure systems and slightly eased the heat, the influence of a mobile high-pressure system in the lower atmosphere led to continued clear skies. Consequently, average temperatures remained high.

6) Reduced Radiative Cooling Effect

  • The increase in atmospheric water vapor hindered radiative cooling, making it difficult for temperatures to drop sufficiently at night — resulting in the continued occurrence of tropical nights.

7) The Impact of Climate Change and Human Activities

  • July 2024 was an unusual month marked by the simultaneous occurrence of strong southerly winds and high humidity levels.
    This phenomenon cannot be fully explained by natural causes alone and is interpreted as being influenced by climate change.

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