Kongju University links stronger Korean downpours to climate change, increased water vapor

Localized heavy rain is a phenomenon where a large amount of rain falls intensively over a narrow area. Since 2019, summer precipitation has increased mainly in the central and Chungcheong regions rather than the south, leading to more cases of extreme downpours. Getty Images Bank

In recent years, damage from localized summer downpours has been increasing, particularly in the central and Chungcheong regions of South Korea. This has been attributed to a combination of climate change, which has strengthened the monsoon formation mechanism over the central Korean Peninsula, and an increased flow of water vapor from the peninsula’s southwest.

Jang Eun-chul, a professor in the Department of Atmospheric Sciences at Kongju National University, explained during a Korea Meteorological Administration press lecture on the 8th, “A clear change has been identified recently, where the expansion of the North Pacific High has intensified the monsoon formation mechanism in the central and Chungcheong regions as it meets warm air from the south of the Korean Peninsula.”

An analysis suggests that the increased supply of water vapor, the key ingredient for precipitation, has also influenced the intensity of localized downpours in the country. The “atmospheric river,” a stream of water vapor flowing into the Korean Peninsula from the Western Pacific and the South China Sea, has also been found to have a stronger impact recently.

Localized downpours are a phenomenon where a large amount of rain falls intensively over a narrow area. Since 2019, summer precipitation has increased, centered on the central and Chungcheong regions rather than the south, leading to a rise in cases of extreme downpours.

The reason localized downpours are drawing attention is their high potential for causing damage. Indeed, damage is more closely related to hourly precipitation than total rainfall. Urban flooding is directly linked to drainage capacity, and river flooding is tied to the river’s water discharge volume.

Atmospheric phenomena have a characteristic where their time and spatial scales are linearly proportional. Localized downpours, which are small in spatial scale, also have a small time scale from their start to dissipation. This means it is difficult to identify their precursor signs.

Professor Jang emphasized, “For phenomena with small spatiotemporal scales like localized downpours that can end within 30 minutes, it is virtually impossible to observe precursor signs with enough lead time to make a prediction.”

He added, “A perfect observation network theoretically means continuous observation at all points with a spacing of at least 2-3 km, including on the ground and in the upper atmosphere. It also requires measurements at one-minute intervals, which is practically impossible.”

Although it is difficult to fully predict localized downpours with current technology, analysis suggests that intensive monitoring is needed to secure a “golden time” through emergency alerts before these downpours lead to damage.

Professor Jang explained, “There is definitely a time buffer before actual damage occurs, such as the time it takes for river water to accumulate and flow downstream after rainfall. If we can immediately detect and report the phenomenon’s occurrence, we can secure that golden time. This is why we must focus on monitoring.”

The need for a larger-scale interpretation to explain localized downpours was also raised. This is because energy transfer within the atmosphere mostly proceeds from large scales to small scales.

Professor Jang stated, “There is a tendency to perceive the monsoon and showers as unrelated events. Even when dealing with localized downpours, it’s important to view them as a system tied to global and Asian-scale phenomena.”

He further explained, “Cases where mesoscale weather phenomena like localized downpours occur like ‘cells’ within the large-scale monsoon front, causing concentrated heavy rain, have always existed. It’s just that their intensity has recently increased.”

Professor Jang said, “South Korea’s ground observation network is relatively well-maintained and dense. However, since the majority of the network is concentrated in Seoul and the metropolitan area, it would be beneficial to fill in the gaps in mountainous regions to avoid missing events like landslides.” He expressed hope that innovative progress could be made if observation equipment capable of real-time monitoring of the upper atmosphere is eventually established.

Meanwhile, an analysis suggests it is difficult to jump to conclusions about the domestic impact of the recently highlighted ‘Super El Niño.’ The Korea Meteorological Administration explained, “The influence of hot winds from the Indian Ocean or cold, dry air from the north has a higher correlation with domestic heatwaves and heavy rain than El Niño and La Niña do.”