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Data Assimilation
in Climate and Energy
Systems Engineering

 Gangnam, Seoul, 
 Heavy rain in August 2022 

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Overview

  • An example of large-scale flooding damage that occurred in the Gangnam-gu, Seocho-gu, and Dongjak-gu areas of Seoul on August 8–9, 2022, due to localized heavy rain caused by a stationary front.

  • In Sindaebang-dong, Dongjak-gu, Seoul, rainfall of 141.5 mm was recorded in one hour, breaking the record for the highest rainfall in 80 years, and widespread damage occurred throughout the city center, including the flooding of the area around Gangnam Station and all stations on Line 2 and the Shinbundang Line.

Scale and period of damage

  • Deaths: 15 or more

  • Key period of damage: Around 9 PM on August 8

  • Casualties caused by basement flooding, Gangnam Station area completely submerged

Official Press Release from the Korea Meteorological Administration

The heavy rains in August 2022 occurred as atmospheric flow became stagnant due to the development of a high-pressure ridge near the Ural Mountains and the Kamchatka Peninsula. Consequently, cold, dry air flowed in from the northwest of Korea, while hot, humid air flowed in strongly from the southwest under the influence of the North Pacific High.

 

As these two air masses with different properties collided strongly near the central region, a stationary front formed, resulting in extremely heavy torrential rains accompanied by thunder and lightning.

 

In particular, in Seoul and the southern Gyeonggi region, extreme precipitation exceeding 100 mm per hour was concentrated over a short period, causing urban flooding damage to escalate rapidly.

AWS/ASOS observation data

Maximum Hourly Precipitation

  • 116 mm/hr (August 8, 2022, 9:35 PM, based in Gangnam-gu)

  • 141.5 mm/hr (August 8, 2022, 21:06, based in Dongjak-gu)

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Cumulative Precipitation

  • August 8 : 24-hour cumulative 326.5 mm (Based on AWS, Ilwon-dong, Gangnam-gu)

                         381.5 mm (Based on AWS, Sindaebang-dong, Dongjak-gu)

  • August 9 : 24-hour cumulative 137 mm (Based on AWS, Ilwon-dong, Gangnam-gu)

                         133.5 mm (Based on AWS, Sindaebang-dong, Dongjak-gu)

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Radar Observation

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(1) 2022.08.08 19:00

  • A strong convective precipitation band began to develop centered on the southern metropolitan area.

  • A linear precipitation band formed extending from southern Gyeonggi to Seoul.

  • Strong precipitation cores began to appear around Gangnam.

(2) 2022.08.08 20:45

  • A very strong precipitation core (red to purple) was concentrated in southern Seoul.

  • The precipitation band stalled in a narrow area, exhibiting a train echo pattern.

  • An event in which extreme rainfall was concentrated in the Gangnam area over a short period.

(3) 2022.08.09 01:01

  • A strong linear band of precipitation persisted over the metropolitan area for an extended period.

  • Precipitation continued to develop as water vapor flowed in continuously from the West Sea.

  • Flooding damage has expanded due to increased accumulated precipitation.

Key Causes

  • At the time, a stationary front and strong atmospheric instability had formed over the Seoul metropolitan area. Strong convection developed as hot and humid air continuously flowed in from the West Sea and the southern seas.

  • Atmospheric instability was maximized as strong updrafts were further intensified by the influence of the upper-level jet stream and upper-level trough.

  • In particular, a very narrow and intense band of precipitation remained stagnant for a long time in the Gangnam area of ​​Seoul, causing severe torrential downpours in a short period.

  • A train echo* pattern appeared, where strong rain clouds repeatedly developed and moved within the same area, and heavy rain of nearly 100 mm per hour was recorded.

 *Train echo: A phenomenon where rain clouds pass continuously along the same path like a train, concentrating precipitation in a specific area.

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