여름철 양자강 저염수의 유입과 그 원인

문재홍,방익찬 濟州大學校 海洋硏究所 2003 해양과환경연구소 연구논문집 Vol.27 No.-

관측자료분석결과 여름철 제주도 주변해역에 출현하는 저염수는 저염현상이 강한 경우에 수직혼합이 약화되어 수온이 주변해역보다 상승하는 특징을 보이고. 우리나라로 유입될 때 제주해협을 지나거나 제주도 남부해역을 지나는 등의 다양한 경로를 나타내기도 한다. 또한 양자강 저염수는 양자강 입구와 제주도 사이에서 보다 고염의 해수에 의해서 분리되어 분포하기도 하는데 이러한 현상은 지속적으로 나타나는 특징으로 보인다. 제주도 주변해역에 나타나는 양자강 저염수의 염분은 제주도 주변의 강수량보다는 오히려 양자강 주변의 강수량과 관련이 있으며 태풍, 바람 등의 기상요인들과도 관계를 보인다. 여름철에 양자강 저염수가 우리나라 해역으로 유입되는 역학을 이해하기 위해서 그 원인으로 알려져 있는 양자강 유출수의 증가, 대만난류의 증가. 바람의 변화를 중심으로 수치모델(ROMS)을 사용하여 실험하였다. 모델결과에 의하면 양자강 유출량과 대만난류의 증가만으로는 양자강 저염수의 유입을 설명하기는 어려우며. 바람이 양자강 저염수의 이동을 결정적으로 지배하고 있는 것으로 나타났다. 그 이유는 양자강 저염수가 흐르는 해역이 비교적 수심이 얕고 해류가 강하지 않아서 바람의 영향이 크게 미치기 때문이다. 그러므로 1996년과 1998년도의 실측바람을 사용한 모델실험에서 양자강 저염수의 유입경로가 정확하게 재현될 수 있었다. 인공위성부이의 궤적을 재현하기 위한 모델결과는 실제부이의 궤적을 아주 비슷하게 재현하였다. 아직은 실제와 다르게 나타나는 부분이 있으며 그 이유가 모델이 강한 대마해류를 잘 재현하지 못하고 있어서 인지 아니면 사용된 일 바람자료보다 더 작은 규모의 강한 바람의 영향 때문인지는 분명하지 않다. 하지만 부이궤적과 같은 작은 규모의 이동이 수치모델을 통해서 재현이 된다는 사실은 앞으로 모델이 보안이 될 경우에 양자강 저염수의 예측이 상당히 정확하게 예측될 수 있음을 의미하는 것이다. 이밖에도 모델결과들은 몇 가지 중요한 결과를 보여주는데, 여름철에 서해안을 따라 북상하는 흐름이 바람에 의한 것이라는 것과 양자강 저염수의 대부분이 지금까지 알려져 왔듯이 남해안을 통해 동해로 흘러가는 것이 아니라 황해로 유입되고 있으며 그 저염수는 황해에서 계절에 따른 바람에 의해 반 시계 방향으로 순환한다는 것이다. The analysis of hydrographic data shows that Yangtze coastal water in the adjacent seas of Cheju Island during summer has a little higher temperature than adjacent water due to weak vortical mixing and various routes such as flowing to the Cheju Strait or to the south of Cheju Island. The distribution of Yangtze coastal water is frequently observed to be separated with more saline water between Yangtze river mouth and Cheju Island showing a disconnection of salinity. This disconnection seems to be persistent. The salinity value of Yangtze coastal water appeared in the adjacent seas of Cheju Island in summer shows closer relation with the precipitation around Yangtze river than around Chtju Island and some relation with meteorological factors such as Typhoon and monsoon wind. In order to understand what drives Yangtze coastal water to the adjacent seas of Korean Peninsula in summer. numerical experiments with ROMS are performed using the factors which are known as its cause such as the increase of Yangtze coastal water. the increase of Taiwan Current. and the change of wind direction. As a result. the Phenomenon can not be driven only by the first two factors but decisively driven by the last one(wind) The reason is because the areas in which Yangtze coastal water flows is shallow and not influenced by strong current so that the wind effect can be dominant. Therefore. the flow of Yangtze coastal water can be satisfactorily simulated by the numerical experiment with the satellite wind stress in 1996 and 1998. We can closely reproduce the trajectories of satellite-tracked drifters released in June 2003 by the numerical model. However. some of model trajectory are still different from the buoy trajectory specially in the area of strong current expected. It is not clear the reason is whether the model does not reproduce strong Tsushima Current well or the large or (1°×1°) scale wind stress used in the model does not represent small scale strong wind stress well. In spite of such a discrepancy. we can have a confidence to expect a sufficiently accurate prediction by some improvements in the future from the success of reproducing small scale movement such as buoy trajectory in numerical model. Besides. the model results show another important facts as follows: the northward flow along the west coasts of Korean Peninsula In summer is caused by wind. most of Yangtze coastal water flow into the Yellow Sea instead of to the East Sea. and the low salinity water rotates counterclockwise in the Yellow Sea by monsoon wind.

Shifts in Multi-decadal Sea Level Trends in the East/Japan Sea over the Past 60 Years

문재홍,이준호 한국해양과학기술원 2016 Ocean science journal Vol.51 No.1

Data derived from altimetry shows that since 1993 the mean sea level over the East /Japan (EJS) Sea is increasing at a rate of ~3 mm/year, but tide gauge records indicate that a multidecadal reversal trend occurred prior to the early 1980s. We here characterize and quantify the multi-decadal trend of mean sea level in the EJS from the reconstructed sea levels and the in-situ ocean profiles over the past 60 years. Our analysis shows that sea level trends have undergone a shift, revealing a declining trend before the early 1980s, followed by a rising trend from the early 1980s onward with a near basin-wide sea level fluctuation. The trend reversal strongly corresponds to changes in the upper-ocean heat content over the EJS, revealing a negative correlation with the Pacific Decadal Oscillation (PDO) index that correlates negatively with wind stress curl (WSC) in the subtropical North Pacific. The PDO-related WSC, which changes the transport of the western boundary current in the subtropical gyre, may account for the observed trend reversal in the EJS sea level on a multi-decadal time scale.

자아 이미지 유형별 펜션의 선택속성과 ?⊙럿?

문재홍(Jae-Hong Moon),최용복(Yong-Bok Choi) 제주대학교 관광과경영경제연구소 2019 産經論集 Vol.39 No.4

Purpose – The purpose of this study is to identify the optional attributes that are important factors in visiting the pension after segmenting the market by self-image type for tourists who visited the pension in Jeju Island. The relations between with the demographic characteristics, tourism patterns, and the degree of satisfaction are analyzed. In addition, through this, the direction of Jeju pension business are offered for proper marketing establishment of future pension business. Research design, data, and methodology - The data was collected by convenience sampling method. The survey was conducted for pension lodge visitors among Jeju tourists. The questionnaire was designed and distributed to the visitors by self-administered questionnaire (SAQ) .The survey was proceeded from August 16, 2019 to August 23, 2019. A total of 330 copies were distributed and 313 copies were used for analysis. Frequency analysis was performed to identify the general characteristics of the sample. Factor analysis and reliability analysis were conducted to verify the reliability and validity of the attractive factors of tourist destinations. Results – According to the cross-analysis between selfimage type and demographic characteristics, there was a significant difference between groups by sex, age and occupation, but there was no difference between groups by household monthly average income. According to the location of tourist attractions, beautiful building design, and various accommodations, there was a significant difference (p <0.05) through the one-way dispersion analysis and post-assessment among the tourist attraction selection attributes by the self-image type of Jeju tourist visitors. In terms of facilities, colorful event shows, good access, historical attractions, and friendly staff, there were significant differences among the communities. Conclusions - This study was performed a cluster analysis on factors by self-image type for tourists visiting Jeju Pension, and tried to grasp the intention of revisit according to the demographic characteristics, pension selection attributes, and visitor s satisfaction. In order to increase satisfaction, efforts should be made to enhance the selectivity, perceived value, and self-efficacy of tourism. Most of the factors that are shown to be important to the tourists can be used for policy and marketing planning for Jeju tourism development in the future.

온천관광지의 선택속성과 만족에 관한 연구

문재홍(Moon Jae Hong),최용복(Choi Yong Bok) 제주대학교 관광과경영경제연구소 2015 産經論集 Vol.35 No.-

봄철 제주도 서부해역의 수괴 분포와 수온역전 특징

강소영,문재홍 한국해양과학기술원 2022 Ocean and Polar Research Vol.44 No.3

Using the results of CTD casts made in Spring from 2017 to 2021, in this study we investigated the water mass distribution and occurrence of temperature inversion in the western seas of Jeju Island in spring. The distribution of water masses was characterized by cold and fresh water in the northwest and warm and saline water in the southeast, forming a strong thermohaline front running in the southwest-to-northeast direction. Strong temperature inversion mainly occurred in the frontal boundary when the cold water intrudes beneath the warm water at depths of 30–50 m. Analysis of the mixing ratio demonstrated that Jeju Warm Water is dominantly distributed in the western seas of Jeju Island, but its ratio can be modified depending on the southward extension of Yellow Sea Cold Water (YSCW). Results of in situ measurement showed that in 2020, the YSCW largely expanded to the western seas of Jeju Island, occupying approximately 40 % of the mixing ratio. Due to the expansion of YSCW, a strong thermohaline front was formed in the study area, thereby causing thick and strong temperature inversion. On the other hand, in 2018 the mixing ratio of YSCW was minimum (~18%) during the study period of 2017–2021, and thus a relatively weak frontal boundary was formed, without the occurrence of temperature inversion. The observational results also suggest that the interannual changes of water mass distribution and the associated temperature inversion in the western seas of Jeju Island are closely related with wind-driven Yellow Sea circulation in spring, which is the summer monsoon transition period.

고해상도 해양순환모델을 활용한 제주도 주변해역의 해수유동 특성

차상철,문재홍 한국해양과학기술원 2020 Ocean and Polar Research Vol.42 No.3

With the increasing demand for improved marine environments and safety, greater ability to minimize damages to coastal areas from harmful organisms, ship accidents, oil spills, etc. is required. In this regard, an accurate assessment and understanding of current systems is a crucial step to improve forecasting ability. In this study, we examine spatial and temporal characteristics of current systems in the adjacent seas of Jeju Island using a high-resolution regional ocean circulation model. Our model successfully captures the features of tides and tidal currents observed around Jeju Island. The tide form number calculated from the model result ranges between 0.3 and 0.45 in the adjacent seas of Jeju Island, indicating that the dominant type of tides is a combination of diurnal and semidiurnal, but predominantly semidiurnal. The spatial pattern of tidal current ellipses show that the tidal currents oscillate in a northwest-southeast direction and the rotating direction is clockwise in the adjacent seas of Jeju Island and counterclockwise in the Jeju Strait. Compared to the mean kinetic energy, the contribution of tidal current energy prevails the most parts of the region, but largely decreases in the eastern seas of Jeju Island where the Tsushima Warm Current is dominant. In addition, a Lagrangian particle-tracking experiment conducted suggests that particle trajectories in tidal currents flowing along the coast may differ substantially from the mean current direction. Thus, improving our understanding of tidal currents is essential to forecast the transport of marine pollution and harmful organisms in the adjacent seas of Jeju Island.

Modeling the Largest Inflow of Changjiang Freshwater into the Yellow Sea in 2012 with Particle-Tracking Experiment

홍지석,문재홍,이준호,방익찬 한국해양과학기술원 2016 Ocean science journal Vol.51 No.4

Abnormally low-salinity water originating from the Changjiang River (CR) was observed at the central Yellow Sea (YS) in 2012, which was quite unique compared to other years. In this study, the intrusion process of the Changjiang Diluted Water (CDW) into the YS interior was examined using a hindcast simulation (2003–2012) with particle-tracking experiments. The particles representing the behavior of the CDW were released at the CR mouth from May to August, and then tracked. The simulated salinity patterns coincide fairly well with those derived from observations, particularly showing a large low-salinity structure around the central YS in 2012. A substantial intrusion of freshwater into the YS occurred in 2012, and this accounted for approximately 16% of all the released particles in 2012 which is twice as high as the mean average covering the 10 years. According to the trajectories in 2012, the particles took less than 50 days to travel from the mouth to the YS interior and followed mainly two paths toward the YS. One pathway traveled northward to the central entrance of the YS and then reached the western coast of Korea. This pathway was attributed to the strong easterly winds in late June and early August when three consecutive typhoons passed through the YS, which was a unique pattern that is rarely found in other years. The other pathway involved particles trapped along the Jiangsu coast drifting farther to the north up to the Shandon Peninsula against the anticyclonic tidal residual circulations during the passage of typhoons.

위성 고도계와 해수면 재구성 자료를 이용한 기후변동성에 따른 태평양 해수면 변화

차상철,문재홍 한국해양과학기술원 2018 Ocean and Polar Research Vol.40 No.1

Previous studies have indicated a great regional difference in Sea Level Rise (SLR) in the Pacific and it has been suggested that this is linked to climate variability over the past two decades. In this study, we seek to identify the possible linkage between regional sea level and Pacific climate variability from altimetry-based sea level data (1993−2012) and further investigate how the Pacific sea level has changed spatially and temporally over the past 60 years from long-term sea level reconstruction data (1953−2008). Based on the same method as Zhang and Church (2012), the Inter-annual Climate Index (ICI) associated with the El Niño-Southern Oscillation (ENSO) and the Decadal Climate Index (DCI) associated with Pacific Decadal Oscillation (PDO) are defined and then the multiple variable linear regression is used to analyze quantitatively the impact of inter-annual and decadal climate variability on the regional sea levels in the Pacific. During the altimeter period, the ICI that represents ENSO influence on inter-annual time scales strongly impacts in a striking east-west “see-saw mode” on sea levels across the tropical Pacific. On the other hand, the decadal sea level pattern that is linked to the DCI has a broad meridional structure that is roughly symmetric in the equator with its North Pacific expression being similar to the PDO, which largely contributes to a positive SLR trend in the western Pacific and a negative trend in the eastern Pacific over the two most recent decades. Using long-term sea level reconstruction data, we found that the Pacific sea levels have fluctuated in the past over inter-annual and decadal time scales and that strong regional differences are presented. Of particular interest is that the SLR reveals a decadal shift and presents an opposite trend before and after the mid-1980s; i.e., a declining (rising) trend in the western (eastern) Pacific before the mid- 1980s, followed by a rising (declining) trend from the mid-1980s onward in the western (eastern) Pacific. This result indicates that the recent SLR patterns revealed from the altimeters have been persistent at least since the mid-1980s.

태풍 경로에 따른 제주 우도수로에서의 해류와 파랑 특성 변화

홍지석,문재홍,윤석훈,윤우석 한국해양과학기술원 2021 Ocean and Polar Research Vol.43 No.4

A shallow channel between Jeju and Udo Islands, which is located in the northeastern Jeju Island, is influenced by storm- or typhoon-induced currents and surface waves as well as strong tidal currents. This study examines the typhoon-induced current and wave patterns in the channel, using Acoustic Doppler Current Meter (ADCP) measurements and an ocean-wave coupled modeling experiment. Three typhoons were chosen - Chaba (2016), Soulik (2018), and Lingling (2019) - to investigate the responses of currents and waves in their pathways. During the pre-typhoon periods, dominant northward flow and wave propagation were observed in the channel due to the southeasterly winds before the three typhoons. After the passage of Chaba, which passed over the eastern side of Jeju Island, the northward flow and wave propagation were totally reversed to the opposite direction, which was attributed to the strong northerly winds on the left side of the typhoon. In contrast, in the cases of Soulik and Lingling, which passed over the western side of Jeju Island, strong southerly winds on the right side of the typhoons continuously intensified the northward current and wave propagation in the channel. The model-simulated current and wave fields reasonably coincided with observational data, showing southward/northward flow and wave propagation in response to the right/left side of the typhoon pathways. Typhoon-induced downwind flows, and surface waves could enhance up to 2m/s and 3m due to the strong winds that lasted for more than 12 hours. This suggests that the flow and wave patterns in the Udo channel are highly sensitive to the pathway of typhoons and accompanying winds; thus, this may be a crucial factor with regard to the movement of seabed sediments and subsequent coastal erosion.

앙상블 경험적 모드 분해법을 사용한 태평양의 지역별 해수면 변화 분석

차상철,문재홍 한국해양과학기술원 2019 Ocean and Polar Research Vol.41 No.3

Natural variability associated with a variety of large-scale climate modes causes regional differences in sea level rise (SLR), which is particularly remarkable in the Pacific Ocean. Because the superposition of the natural variability and the background anthropogenic trend in sea level can potentially threaten to inundate low-lying and heavily populated coastal regions, it is important to quantify sea level variability associated with internal climate variability and understand their interaction when projecting future SLR impacts. This study seeks to identify the dominant modes of sea level variability in the tropical Pacific and quantify how these modes contribute to regional sea level changes, particularly on the two strong El Niño events that occurred in the winter of 1997/1998 and 2015/2016. To do so, an adaptive data analysis approach, Ensemble Empirical Mode Decomposition (EEMD), was undertaken with regard to two datasets of altimetry-based and in situ-based steric sea levels. Using this EEMD analysis, we identified distinct internal modes associated with El Niño-Southern Oscillation (ENSO) varying from 1.5 to 7 years and low-frequency variability with a period of ~12 years that were clearly distinct from the secular trend. The ENSO-scale frequencies strongly impact on an east-west dipole of sea levels across the tropical Pacific, while the low-frequency (i.e., decadal) mode is predominant in the North Pacific with a horseshoe shape connecting tropical and extratropical sea levels. Of particular interest is that the low-frequency mode resulted in different responses in regional SLR to ENSO events. The low-frequency mode contributed to a sharp increase (decrease) of sea level in the eastern (western) tropical Pacific in the 2015/2016 El Niño but made a negative contribution to the sea level signals in the 1997/1998 El Niño. This indicates that the SLR signals of the ENSO can be amplified or depressed at times of transition in the low-frequency mode in the tropical Pacific.