Abstract
The long-term trend of swell-like waves invading the east coast of Korea was identified by using observations and hindcast data from 1979 to 2016. We defined a swell-like wave as a wave with a height of 2 m and a peak period of 10 s on the basis of a literature review of human casualties and property damage in the region. In total, 179 swell-like wave cases were detected from 1979 to 2016, with 132 cases caused by extratropical cyclones (ETCs). The track density analysis indicated that the ETCs were mainly generated on the east coast of China, over the East/Japan Sea, and over the Kuroshio-Oyashio extension region and then moved northeast. This reflects the prevailing wind direction, which was the most significant factor in generating the swell-like waves. The number of swell-like waves has been significantly increasing since the 2000s. This increasing trend of swell-like waves is linked with the synoptic eddy activity with a correlation of 0.53. They were associated with the reversed meridional gradient of surface air temperature and the consequent negative vertical wind shear anomaly near 40° N.
Highlights
High wind waves, mainly generated in the East/Japan Sea (EJS), frequently occur due to extratropical cyclones (ETCs) passing through the EJS during autumn and winter [1,2,3,4]
The damage to human life and property caused by swell-like waves on the east coast of Korea was investigated in the period of October 2005–August 2018
ETCs in winter are essential for the generation of swell-like waves, we only considered the wave heights and periods that can affect the coast as swell-like waves to examine their occurrence and determining factors
Summary
High wind waves, mainly generated in the East/Japan Sea (EJS), frequently occur due to extratropical cyclones (ETCs) passing through the EJS during autumn and winter [1,2,3,4]. Kitaide [1] demonstrated that abnormal high swell waves (or a Yorimawari Waves) are generated due to the solid north-easterly winds formed by a quasi-stationary low-pressure system. Jeong et al [10] and Oh et al [11] demonstrated that these waves, called swell-like waves, frequently occur under clear weather conditions over the coastal region because they originate from the central or eastern EJS. These swell-like waves usually last two to three days in winter and can cause property damage and human casualties in coastal areas
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