hankyoreh

July 27.

By Ryu Seon-hee

Climatologically speaking, it was a flood that combined all the worst possible elements. The monsoon season finished on July 17, but now Seoul has been hit by a deluge due to a strange distribution of air pressure.

The main cause of this downpour was unstable air in the skies above the central region of South Korea. Generally, warm, light air stays in the upper layer of the atmosphere and cold, heavy air in the lower layer. This time, however, warm air from a northern Pacific anticyclone flowed into the mid and lower layers, causing further instability. When this happens, heavy rain falls for a short period in specific areas. Because of this, new hourly precipitation records were set in several areas.

On the morning of July 27, an automatic weather station in Seoul’s Gwanak District measured 110.5mm of rain per hour (4.4 inches per hour), although this was not included in the Korea Meteorological Administration’s (KMA) official statistics.

Such powerful banks of rain clouds normally pass by in a few hours. This time, however, a cold anticyclone near Russia’s Sakhalin blocked their way. As this configuration of air pressure persists, heavy rain continues to fall.

In South Korea, the pattern of a monsoon season followed by a period of sweltering weather is being broken. Even after the monsoon front dies out, heavy and localized downpours, like the current one, resulting from atmospheric instability continue until September. There is no longer a long-term forecast of when the monsoon will begin and end.

“Since 2000, especially, such heavy local downpours after the monsoon have occurred frequently,” said Jeong Gwan-yeong, a forecast analyst at the KMA. “The phenomenon of increasing regional and temporal discrepancies in rainfall, too, can be seen, in a broad sense, as a consequence of climate change.”

Indeed, levels of precipitation differed even within Seoul itself. On July 26, 171mm of rain fell on Seoul, while 16.5mm fell on Incheon, barely 30km away. From July 26 until 5pm on July 27, cumulative rainfall upon Seoul was well more than twice that upon Incheon.

The phenomenon whereby rainfall is concentrated into a specific period of time, too, is becoming more pronounced. In Seoul, in the 24 hours between 4 p.m. on July 26, when rain began falling, and 4 p.m. the next day, the amount of rain that fell was 433.5mm. This was equivalent to more than half the 802mm that fell during the entire 26 days of the monsoon season. As of 4 p.m. on July 27, the total rainfall since the first day of the monsoon, just over one month ago, stands at 1235.5mm, or 85 percent of Seoul’s annual average of 1450.5mm.

It appears that this rain will continue in the central regions of South Korea and only stop in the afternoon of July 29. Up to 250mm more is set to fall in some regions of Seoul, Gyeonggi Province and the western part of Gangwon Province, while in some areas cumulative rainfall since July 26 will surpass 600mm.

Meanwhile, it has come to light that the people that lost their lives in a landslide in the Chuncheon area were 10 university students from an Inha University inventors‘ society called “Idea Bank.” The students, who traveled to the region on July 25 in order to work voluntarily at an “invention camp” for students at a local elementary school, had finished their volunteer activity and were resting in a pension when the disaster struck.

Founded in 2002, Inha University’s Idea Bank is a society that all students interested in invention can join, regardless of major. Since then, it has consistently performed well at competitions such as the “Invent Korea” tournament for students, and is said to have run a four-day invention and science camp at a rural school in July of last year, too. 35 of its 80 members took part in this year‘s event. In addition to the ten that were killed, four suffered heavy, including spinal, injuries, while 16 others were injured to various extents.

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