• Journal of the Korean earth science society
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• v.28 no.7
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• pp.947-956
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• 2007

In this article, the extratropical transition (ET) of tropical cyclone (TC) was investigated based on the case study covering the latest three TCs (Shanshaa Yaki, and Soulik) associated with ET evolution (onset and completion) using the objective 37 diagnostics of Evans and Hart (2003) and Hart (2003). At 500-hPa level, on an onset of ET, all three TCs entered the baroclinic zone. In a vertical cross-section analysis, three TCs before and at an onset of ET kept warm and humid throughout all levels around the TC center. However, these TCs after ET onset became relatively cold and dry over the western part of TC as the typical characteristics of ET concept model. Although our case study was not sufficient, it is concluded that the diagnostics of the ET onset and atmospheric structure change associated with Evans and Hart (2003) and Hart (2003) will be useful in ET operational forecast.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.3
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• pp.168-174
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• 2015

Characteristics of high waves occurred in winter season on the west coast of Korea were investigated by analyzing the wave data observed at five observation locations. Records of four different high waves were subjected to the analysis together with the corresponding meteorological data during those time periods. The significant wave height reached its maximum of 6.42 m on December 4th, 2005. It was clarified that the high waves occurred due to strong wind fields that were formed over the west sea of Korea when the extra-tropical cyclone was excessively developed. Characteristics of the high waves generated in the west sea seemed to be predominantly wind sea as the temporal variation of the wave height at the coast were closely related to those of the wind speed measured at neighboring weather stations.

• Journal of the Korean earth science society
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• v.31 no.4
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• pp.322-334
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• 2010

Spatiotemporal characteristics of precipitation in Korea, associated with the weakening of Tropical Cyclones (TCs) around the Korean Peninsula ($32-36^{\circ}N$, $122-132^{\circ}E$) over the last 30 years (1979-2008), were investigated. Weakened TCs are classified as WEC (Weakened to Extratropical Cyclone) and WTD (Weakened to Tropical Depression). In WEC, precipitation was evenly distributed all over the Korean Peninsula and the greater precipitation was recorded in the southern coast. In WTD, the most precipitation was recorded in the southern coast but low precipitation was recorded in the central and inland areas of Korea. The difference of precipitation between WEC and WTD was not statistically significant in Region 2 (Jeollanam-do, Gyeongsangnam-do, southeastern part of Gyeongsangbuk-do, Jeju-do); however, the precipitation resulting from WEC was greater than that resulting from WTD in Region 1 (central area of Korea, Jeollabuk-do, inland of Gyeongsangbuk-do). In WEC, the developed upper-level potential vorticity (PV) and low-level temperature trough shifted to the northwest of TCs approaching Korea. In addition, an upper-level jet stream and strong divergence field were observed to the northeast of the TCs. It was assumed that these meteorological factors had induced baroclinic instability and diabatic process, which created a large precipitation area around the TCs. However, the intense PV, temperature trough, jet stream were not observed in WTD, which created a small precipitation area around the TCs.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.29 no.4
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• pp.206-216
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• 2017

The temporal distribution of the turbulence kinetic energy (TKE) and the vertical component of Reynolds stresses ($-{\bar{u^{\prime}w^{\prime}}}$) was measured during one wave period under high wave energy conditions. The wave data were obtained at Hujeong Beach in the east coast of Korea at January 14~18 of 2017 when an extratropical cyclone was developed in the East Sea. Among the whole thousands of waves measured during the period, hundreds of regular waves that had with similar pattern were selected for the analysis in order to give three representing mean wave patterns using the ensemble average technique. The turbulence properties were then estimated based on the selected wave data. It is interesting to find out that $-{\bar{u^{\prime}w^{\prime}}}$ has one clear peak near the time of flow reversal while TKE has two peaks at the corresponding times of maximum cross-shore velocity magnitudes. The distinguished pattern of Reynolds stress indicates that vertical fluxes of such properties as suspended sediments may be enhanced at the time when the horizontal flow direction is reversed to disturb the flows, supporting the turbulence convection process proposed by Nielsen (1992). The characteristic patterns of turbulence properties are examined using the CADMAS-SURF Reynolds-Averaged Navier-Stokes (RANS) model. Although the model can reasonably simulate the distribution of TKE pattern, it fails to produce the $-{\bar{u^{\prime}w^{\prime}}}$ peak at the time of flow reversal, which indicates that the application of RANS model is limited in the prediction of some turbulence properties such as Reynolds stresses.