Korea Institute of Ocean Science and Technology (KIOST, president Kim Woong-seo) has confirmed the rapid intensification (RI)¹⁾  of no. 2 Typhoon Surigae. With such timely and accurate prediction of large typhoons, storm damage will be minimized.

1) Rapid intensification of typhoons (RI) refers to the wind speed of a typhoon increasing to over 15.3m/s within 24 hours. Inflow of excessive thermal energy shortly after the formation of a typhoon, the possibility of rapid intensification of typhoon rises. Generally, in waters at high temperatures, coupled with a large difference in humidity between the sea surface and the atmosphere, water vapor moves from the ocean to the atmosphere, increasing the supply of thermal energy, which strengthens a typhoon.

On April 6, a KIOST research team led by principal research scientist Kang Sok-kuh embarked aboard the research vessel Isabu to conduct research supported by Ministry of Oceans and Fisheries on the ocean-atmosphere interaction and rapid intensification in the Northeast Pacific, and arrived at Jangmokhang Port in Geoje on May 3. Upon the occurrence of Typhoon Surigae on April 13, the team moved to the western Philippine Sea to monitor the rapid intensification of the typhoon. Typhoons are more likely to intensify rapidly when they receive an excessive amount of thermal energy in a short period. To confirm this, the team conducted a site investigation. 
  Observation results showed that sea surface temperature rose above 29°C, a level producing five times as much thermal energy as 26°C, the minimum sea surface temperature at which thermal energy creates a typhoon under the sea-atmospheric condition at the time of observation. In addition, 80 meters below the ocean surface, water temperature was above 26°C, optimal conditions for sending warm sea water to the surface layer. Further, while the exosphere was humid, the mesosphere was dry, with relative humidity of about 20%.

Based on the results of their investigation, KIOST researchers determined that both the ocean and the atmosphere were contributing to the RI of the typhoon. The maximum wind speed of Typhoon Surigae doubled in only 36 hours. On April 16, 15:00 (KST), maximum wind speed was at 41m/s, but surged to 83m/s by 03:00 on April 18.

Typhoon Surigae, the strongest prior to May of this year, became extinct at the northeastern Philippines as it encountered strong west winds during its journey north, fortunately missing the Korean peninsula;  storms that strike the peninsula usually originate in the Philippine Sea. KIOST researchers have noted that a long-term change may have occurred, given that Typhoon Goni, the strongest-ever typhoon (typhoon no.19 in 2020,) and Typhoon Surigae evolved through RI into larger storms during the spring.

Typhoons are accompanied by localized heavy rain, gale-force winds, and tsunamis, causing devastating damage. Climate volatility associated with global warming tends to increase the frequency of large typhoons. To prevent natural disasters, precision in marine climate prediction is essential. KIOST has strived to enhance the accuracy of its marine climate forecasting by accessing marine environmental data collected from the Ocean Research Station and Chollian Satellite 2B through time-series data analysis and date interpretation, as well as by conducting on-site investigation of the Northwest Pacific to study the RI of typhoons.
  KOIST president Kim stated that “In terms of damage from natural disasters, Korea is most heavily impacted by typhoons, but they occur in seas where on-site observation is difficult. By monitoring natural marine phenomena and closely analyzing the data collected, KIOST is dedicated to increasing the accuracy of marine climate forecasts to safeguard both the nation and its assets.”