• 한국수산과학회지
• /
• 제51권3호
• /
• pp.313-320
• /
• 2018

Chub mackerel Scomber japonicus is an economically important pelagic species in the western North Pacific. In the last 50 years, the annual total catch in Korean waters showed large fluctuations, ranging from 100 to $420{\times}10^3tons$. To provide a biological reference point for management of chub mackerel, we applied a simulation-based yield-per-recruit (Y/R) model that considered both temperature-dependent growth and size-dependent mortality. We estimated the fisheries yield with respect to varying biological reference points and environmental conditions, including 1) the instantaneous rate of fishing mortality (F), 2) length of fish at first capture ($L_c$), and 3) water temperature. The result of our analysis showed that the Y/R could be greatest when the $L_c$ ranges from 19-27 cm and F ranges from $1.48-2.00yr^{-1}$. Y/R increases with increased water temperature between 15 and $23^{\circ}C$. We suggest targeting an $L_c$ of 17 cm (age=0.6 years) under the assumed current of $F=0.48yr^{-1}$ for maximizing the chub mackerel harvest. Further analysis considering spawning and recruitment processes are required to provide biological reference points to ensure the sustainability of chub mackerel fisheries in Korean waters.

• 한국해안·해양공학회논문집
• /
• 제24권3호
• /
• pp.166-178
• /
• 2012

서해안에 영향을 미치는 폭풍해일 모의를 위해 비대칭 태풍바람장, 조석 및 파랑의 복합적 현상이 동시에 고려되어 북서태평양까지 확장된 동일한 상세유한요소격자상에서 수행되었다. 비대칭형 태풍 경도풍은 JTWC에서 제공하는 Best track의 4분면 풍속반경 자료 등이 조석유동모형 pADCIRC에 입력되고 파랑모형 unSWAN과 동적 결합되어 병렬클러스터에서 계산된다. 태풍 곤파스(TY1007)에 적용한 모의실험에서 이어도 관측기지의 파랑자료 및 우리나라에 근접한 시간에 관측된 주요 검조소에서의 해수면자료와 매우 잘 일치하는 만족스러운 결과가 도출되었다. 비대칭형 경도풍 고려로 태풍상륙 이남에서 국부적인 해일고 상승이 두드러지게 모의되어 본 연구에서 제안한 방법은 폭풍해일로 인한 해안저지대 및 주요시설물 범람대비 등 연안재해관리에 유용하게 활용될 수 있다.

• Fisheries and Aquatic Sciences
• /
• 제21권4호
• /
• pp.9.1-9.7
• /
• 2018

To establish a comprehensive management strategy, as part of the optimization of cultural practice for an oyster rack culture system, we used a numerical model to estimate the primary production in the waters on the eastern coast of Wando island, South Korea. The estimated primary production ranged from 17.12 to $1052.55mgC\;m^{-2}day^{-1}$ ($204.22{\pm}224.75mgC\;m^{-2}day^{-1}$ in average). Except for the times of peak phytoplankton blooms, the estimated primary production (PP) was consistently under $200mgC\;m^{-2}day^{-1}$, which is more similar to the value of PP measured off the western coast of South Korea than the southern coast. No clear relationship was observed between nitrogen content and rainfall with the exception of heavy rainfall events, indicating that precipitation might not be the main source of nutrients in these waters. No clear influence was observed from Doam tidal discharge, located 24 km north from these waters due to main tide comes in this area from the channel between Gunwe-myeon in Wando island and Pukpyeong-myeon in Haenam-gun. Because of the shallow water depth and strong tidal current, resuspension of sediments, which causes an input of nitrogen into the system, could be easily caused by even mild wind and the infrequent passing of ships. Microscopic examination of the phytoplankton composition showed additional contribution of benthic species such as Paralia sulcata into the waters, which increase the productivity of oyster farms in the waters. The availability of nitrate and phosphate for primary production was temporarily limited throughout most of the spring and autumn blooming season.

• 대기
• /
• 제21권1호
• /
• pp.45-55
• /
• 2011

A definition on the tropical cyclone (TC) that influenced the Korean Peninsula (KP), the KP-influence TC, is widely used in the TC communities, but its criterion is not clear mainly due to the ambiguity and subjectiveness of the term such as 'influence', which led to the inconsistent TC statistical analysis. This study suggests a definition and criterion on the TC approaching to the KP (KP-approach TC) additionally, which is more obvious and objective than the KP-influence TC. In this study, the criterion on the KP-approach TC is determined when the TC's center from the RSMC best track data encounters the box areas of $28^{\circ}N{\sim}40^{\circ}N$ and $120^{\circ}E{\sim}138^{\circ}E$. The range is chosen by finding a minimum area that includes all official KP-influence TCs except three TCs that affected the KP as a tropical depression (TD). Statistical analysis reveals that, among total 1,537 TCs that occur in the western North Pacific during 1951-2008, the KP-approach TC was 472, the KP-influence TC was 187, and the KP-landfall TC was 87. August was the month that the largest TCs approach and influence to the KP. Finally, this paper suggests to determine the KP-influence TC by the strong wind and heavy rain advisories in the KP based on the observation after the storm's passage.

• 대기
• /
• 제20권2호
• /
• pp.111-130
• /
• 2010

An uncertainty assessment for precipitation datasets simulated by Atmosphere-Ocean Coupled General Circulation Model (AOGCM) is conducted to provide reliable climate scenario over East Asia. Most of results overestimate precipitation compared to the observational data (wet bias) in spring-fall-winter, while they underestimate precipitation (dry bias) in summer in East Asia. Higher spatial resolution model shows better performances in simulation of precipitation. To assess the uncertainty of spatiotemporal precipitation in East Asia, the cyclostationary empirical orthogonal function (CSEOF) analysis is applied. An annual cycle of precipitation obtained from the CSEOF analysis accounts for the biggest variability in its total variability. A comparison between annual cycles of observed and modeled precipitation anomalies shows distinct differences: 1) positive precipitation anomalies of the multi-model ensemble (MME) for 20 models (thereafter MME20) in summer locate toward the north compared to the observational data so that it cannot explain summer monsoon rainfalls across Korea and Japan. 2) The onset of summer monsoon in MME20 in Korean peninsula starts earlier than observed one. These differences show the uncertainty of modeled precipitation. Also the comparison provides the criteria of annual cycle and correlation between modeled and observational data which helps to select best models and generate a new MME, which is better than the MME20. The spatiotemporal deviation of precipitation is significantly associated with lower-level circulations. In particular, lower-level moisture transports from the warm pool of the western Pacific and corresponding moisture convergence significantly are strongly associated with summer rainfalls. These lower-level circulations physically consistent with precipitation give insight into description of the reason in the monsoon of East Asia why behaviors of individually modeled precipitation differ from that of observation.

• 대기
• /
• 제26권1호
• /
• pp.159-183
• /
• 2016

On 31 July 2014, there was a localized torrential rainfall ($58.5mm\;hr^{-1}$) caused by a strong convective cell with thunder showers over Daegwallyeong. In the surface synoptic chart, a typhoon was positioned in the East China Sea and the subtropical high was expanded to the Korean peninsula. A WRF (Weather Research and Forecasting) numerical simulation with a resolution of 1 km was performed for a detailed analysis. The simulation result showed a similar pattern in a reflectivity distribution particularly over the Gangwon-do region, compared with the radar reflectivity. According to the results of the WRF simulation, the process and mechanism of the localized heavy rainfall over Daegwallyeong are as follows: (1) a convective instability over the middle part of the Korean peninsula was enhanced due to the low level advection of warm and humid air from the North Pacific high. (2) There was easterly flow from the coast to the mountainous regions around Daegwallyeong, which was generated by the differential heating of the insolation among Daegwallyeong and the Yeongdong coastal plain, and nearby coastal waters. (3) In addition, westerly flow from the western part of Daegwallyeong caused a strong convergence in this region, generating a strong upward motion combined by an orographic effect. (4) This brought about a new convective cell over Daegwallyeong. And this cell was more developed by the outflow from another thunderstorm cell to the south, and finally these two cells were merged to develop as a strong convective cell with thunder showers, leading to the record breaking maximum rainfall per hour ($58.5mm\;hr^{-1}$) in July.

• 대기
• /
• 제27권2호
• /
• pp.199-211
• /
• 2017

The cold surges over East Asia can be grouped to two types of the wave-train and the blocking. Recently, the observational study proposed new dynamical index to objectively identify cold surge types. In this study, the dynamical index is applied to the simulations of 10 climate models, which participate in the Coupled Model Intercomparison Project Phase 5 (CMIP5). Focusing on assessment of cold surge simulation, we discuss characteristic of the wave-train and blocking cold surges in the climate models. The wave-train index (WI) and the blocking index (BI) based on potential temperature anomalies at dynamical tropopause over the subarctic region, the northeast China, and the western North Pacific enable us to classify cold surges in the climate models into two types. The climate models well simulate the occurrence mechanism of the wave-train cold surges with vertical structure related to growing baroclinic wave. However, while the wave-train in the observation propagates in west-east direction across the Eurasia Continent, most of the models simulate the southeastward propagation of the wave-train originated from the Kara Sea. For the blocking cold surges, the general features in the climate models well follow those in the observation to show the dipole pattern of a barotropic high-latitude blocking and a baroclinic coastal trough, leading to the Arctic cold surges with the strong northerly wind originated from the Arctic Sea. In both of the observation and climate models, the blocking cold surges tend to be more intense and last longer compared to the wave-train type.

• 대기
• /
• 제29권5호
• /
• pp.627-637
• /
• 2019

Severe and long-lasting heat waves over Korea and many regions in the Northern Hemisphere (NH) during the 2016 summer, have been attributed to global warming and atmospheric teleconnection coupled with tropical convective activities. Yet, what controls subseasonsal time scale of heat wave has not been well addressed. Here we show a critical role of two dominant boreal summer intraseasonal oscillation (BSISO) modes, denominated as BSISO1 and BSISO2, on modulating temporal structure of heat waves in the midst of similar climate background. The 2016 summer was characterized by La Nina development following decay of strong 2015/2016 El Nino. The NH circumglobal teleconnection pattern (CGT) and associated high temperature anomalies and heat waves were largely driven by convective activity over northwest India and Pakistan during summer associated with La Nina development. However, the heat wave event in Korea from late July to late August was accompanied by the phase 7~8 of 30~60-day BSISO1 characterized by convective activity over the South China Sea and Western North Pacific and anticyclonic circulation (AC) anomaly over East Asia. Although the 2010 summer had very similar climate anomalies as the 2016 summer with La Nina development and CGT, short-lasting but frequent heat waves were occurred during August associated with the phase 1~2 of 10~30-day BSISO2 characterized by convective activity over the Philippine and South China Sea and AC anomaly over East Asia. This study has an implication on importance of BSISO for better understanding mechanism and temporal structure of heat waves in Korea.

• 한국해안·해양공학회논문집
• /
• 제24권5호
• /
• pp.352-365
• /
• 2012

대표적 연안재해인 폭풍해일을 기상예보와 연동하여 신속하게 모의하고 즉각 예보하기 위한 초기 연구가 2012년 8월과 9월 서남해안으로 상륙한 태풍 Bolaven, Tembin 그리고 Sanba에 대해 수행되었다. JTWC 태풍경보에 근거한 신속모의는 반자동화된 방법을 통해 SLOSH 및 ADCIRC 모델에서 수행되었으며, 그 결과가 동화되고 웹에 게시되었다. SLOSH는 PC에서 1시간, ADCIRC로는 57,000개의 절점으로 구성된 북서태평양해역을 64 core의 병렬컴퓨터에서 태풍경보 발효부터 웹 게시까지 전 과정에 2시간이 소요되어 준실시간적인 즉각 예보의 기틀을 마련할 수 있었다. Bolaven에 대해 사후 관측된 해수면과 비교하면 주요 검조소에서 최대해일고는 2개 모형이 RMS 오차 0.17~0.19 m에서 만족하고, 최대해일고 발생시각도 1시간 이내에서 잘 일치하고 있어 상당히 만족스러운 결과로 판단된다.

• 통합자연과학논문집
• /
• 제4권1호
• /
• pp.44-57
• /
• 2011

In general, heavy rainfall in Korea is mostly associated with inflow of 850hPa low-level jet. It transports abundant heat and moisture flux to the Changma front. In this study, synoptic characteristics of heavy rainfall in Korea from a case study is examined by classifying heavy rainfall cases with synoptic patterns, in particular distribution of upper- and low-level jets, western North Pacific high, and moisture flux. The surface and upper-level weather charts including auxiliary analysis chart and radar and satellite images obtained from the Korea Meteorological Administration, and 500hPa geopotential heights from NCEP/NCAR are used and then KLAPS is applied to understand the local atmospheric structure associated with heavy rainfall. Results show that maximum frequency in 60 heavy rainfall cases with more than 150mm/day appears in the Changma type of 43 cases (a proportion in relation to a whole is 52%) including the combined Changma types with typhoon and cyclone. As indicated in previous studies, most heavy rainfall cases are related to inflow of low-level jet. In addition, synoptic characteristics based on the analyses of weather charts, radar and satellite images, and KLAPS in heavy rainfall case of 12 July, 2009 reveal that the atmospheric vertical structure in particular equivalent potential temperature favorable for effective inflow of warm and moist southwesterly into the Changma front is linked to large potential instability and the strong convergence accompanied with low-level jet around Suwon contributes to atmospheric upsliding along the Changma front, producing heavy rainfall.