Although two typhoons passed near Japan in late June without making landfall on the Korean Peninsula, they were analyzed as contributing factors behind the subsequent heat wave and torrential rain.
This is a case in which it is difficult to determine the connection with our weather based solely on whether a typhoon caused damage.
Through what process did typhoons far from the Korean Peninsula alter the seasonal rain front and the North Pacific high?
3-Line Summary
1. Even typhoons that do not make landfall can change the weather
2. The average temperature rose 4.1℃ in 6 days
3. Their impact cannot be determined solely from typhoon tracks
Typhoons Near Japan Changed the Atmospheric Flow
On August 31, the Ocean Climate Prediction Center of the Korea Institute of Ocean Science and Technology (KIOST) said that typhoons that skirted the Korean Peninsula this summer changed the surrounding atmospheric circulation and affected the heat wave in South Korea. The analysis focused on Typhoon No. 7 Mekkhala and Typhoon No. 8 Higos, which passed one after another near Japan in late June.
Although the two typhoons did not directly approach the Korean Peninsula, they were analyzed as having strengthened the activity of the seasonal rain front and precipitation by supplying warm, humid air. At the same time, they pushed the North Pacific high—which has a major influence on summer heat—eastward, temporarily suppressing its expansion toward the Korean Peninsula.
As a result, in early July the Korean Peninsula briefly moved outside the influence of the North Pacific high, and temperatures fell. The explanation is not a simple progression in which it became hot immediately after the typhoons passed far away; rather, the position of the high and the activity of the seasonal rain front changed first. According to a ZDNet Korea report, at the time of the analysis the two typhoons were approximately 847~1051㎞ from the Korean Peninsula.
Heat Released by Torrential Rain Added to the High’s Expansion
Heat was released into the atmosphere during the process of condensation, in which water vapor changes into water droplets. The Prediction Center’s analysis found that the precipitation heating effect produced when large amounts of water vapor condensed and torrential rain fell under the influence of the typhoons strengthened the North Pacific high and created conditions for it to expand its influence toward the Korean Peninsula.
The Prediction Center said that, after applying this effect to a weather analysis model, it confirmed that the North Pacific high strengthened at an altitude of about 5.5㎞ above the area near Japan and expanded again toward the Korean Peninsula. This means that although typhoons, the seasonal rain front, and the high are distinguished by separate names, they can be connected in the actual atmosphere through water vapor, precipitation, and released heat.
An analysis of data from 60 Automated Surface Observing System (ASOS) stations operated by the Korea Meteorological Administration found that the nationwide average temperature on July 1 was 1.3℃ below normal, but on July 7 it was 2.8℃ above normal. The difference from normal amounted to an average increase of 4.1℃ over 6 days. This temperature change was presented as an example from an analysis that examined both the atmospheric influence of a distant typhoon and the precipitation heating effect.
The Fact That a Typhoon Did Not Make Landfall Is Not Enough
More than 20 typhoons formed over the western Pacific this summer, but none made landfall on the Korean Peninsula. Whether a typhoon makes landfall is important information for assessing damage from strong winds and heavy rain, but the key point of this analysis is that it cannot be said that a typhoon had no effect on weather over the Korean Peninsula based on that fact alone.
Kim Seong-hun, director of the Ocean Climate Prediction Center, said that the cause of this year’s heat wave cannot be attributed definitively to a single typhoon based on this case alone. However, he explained that it was a case showing that even typhoons that did not directly approach the Korean Peninsula can affect temperatures by changing the seasonal rain front and the North Pacific high.
The influence left by a typhoon may not remain only in areas reached by its winds. The point to note in this analysis is the sequence in which a typhoon over distant waters first intensified rain, and the heat released by that rain was then connected to changes in the strength of the high. This is why, when understanding heat waves and torrential rain on the Korean Peninsula, it is difficult to isolate atmospheric changes based solely on records of typhoon landfalls.
References
Tags #KoreanPeninsula #Typhoon #HeatWave #TorrentialRain #Mekkhala #Higos #NorthPacificHigh #SeasonalRainFront #PrecipitationHeatingEffect #KoreaInstituteofOceanScienceandTechnology #KIOST #Climate #Weather