• Journal of Navigation and Port Research
• /
• v.31 no.9
• /
• pp.793-799
• /
• 2007

The effect of seasonal wind on the tidal circulation in Jeju harbor was examined by using a numerical shallow water model. A finite element for analyzing shallow water flow is presented. The Galerkin method is employed for spatial discretization. Two step explicit finite element scheme is used to discretize the time function, which has advantage in problems treating large numbers of elements and unsteady state. The numerical simulation is compared with three cases; Case 1 does not consider the effect of wind, Case 2 and Case 3 consider the effect of summer and winter seasonal wind, respectively. According to result considering effect of seasonal wind, velocity of current vector shows slightly stronger than that of case 1 in the flow field. It can be concluded that the present method is a useful and effective tool in tidal current analysis.

• Proceedings of KOSOMES biannual meeting
• /
• 2003.11a
• /
• pp.163-166
• /
• 2003

The seasonal mean wind direction and wind speed in a greater coasting area are investigated using the ECMWF(European Centre for Medium-Range Weather Forecasts) data for 11 years from 1985 to 1995. In winter, the main wind direction in Korea and vicinity, Taiwan and vicinity, and the North Pacific Ocean of middle latitudes is a northwesterly wind, northeasterly wind, and westerly wind respectively. The wind speed is strongest in the East China Sea, the South China Sea, and the North Pacific Ocean of low latitudes(Beaufort wind scale 5-6). A distribution pattern of wind direction in spring and fall is similar to that in winter. Seasonal mean wind speed is strongest in winter and the next is fall. The wind speed in summer is generally weak. However, that in the Indochina and vicinity is strong by the influence of Asian monsoon.

• Nuclear Engineering and Technology
• /
• v.55 no.1
• /
• pp.261-269
• /
• 2023

During a nuclear power plant (NPP) accident, radioactive material may be released into the surrounding environment in the form of a radioactive plume. The behavior of the radioactive plume is influenced by meteorological factors such as wind direction and speed. If the residents are evacuated to a shelter in the direction of the flow of the radioactive plume, the radiation exposure of the residents may increase, contrary to the purpose of the evacuation. To avoid such an undesirable outcome, this paper applies a big data analysis to evaluate the suitability of the shelter locations near 5 NPPs in the Republic of Korea in terms of the seasonal wind direction frequency in those areas. To this end, the wind data measured around the NPPs from 2016 to 2020 were analyzed to derive the seasonal wind direction frequency using a big data analysis. These analyses results were then used to determine how many shelters around NPPs locate in areas with prevailing wind direction per season. Then, suggestions were made on the direction for residents not to evacuate, if possible, that is, the prevailing seasonal wind directions for 5 NPPs, depending on the season in which the accident occurs.

• Atmosphere
• /
• v.17 no.4
• /
• pp.421-433
• /
• 2007

We have investigated the seasonal characteristics of surface turbulent fluxes observed at Ieodo Ocean Research Station from 2005 to 2006. Both 10Hz and 30 minutes flux data are quality controled, and tilt correction is performed in 10Hz data before quality control. The turbulent fluxes of open sea shows clear seasonal variations, though diurnal variations are barely shown. The seasonal ratio of stable and unstable conditions are closely related to the temperature difference between sea surface and air. In stable and semi-stable condition, latent and sensible heat fluxes have very small values without any relationship with wind speed. Though friction velocity shows slightly increasing trend with wind speed, it has many outliers. In unstable condition, turbulent fluxes increased with wind speed. Especially, latent heat flux increased rapidly during DJF. The latent heat flux at high wind speeds is more scatter.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.49 no.12
• /
• pp.963-969
• /
• 2021

The wind data measured from local meteorological masts is used to evaluate wind speed distribution and energy production in the specified site for wind farm However, wind data measured from meteorological masts often contain missing information or insufficient desired height or data length, making it difficult to perform wind turbine control and performance simulation. Therefore, long-term continuous wind data is very important to assess the annual energy production and the capacity factor for wind turbines or wind farms. In addition, if seasonal influences are distinct, such as on the Korean Peninsula, wind data with seasonal characteristics should be considered. This study presents methodologies for generating synthetic wind that take into account fluctuations in both wind speed and direction using the hidden Markov model, which is a statistical method. The wind data for statistical processing are measured at Maldo island in the Kokunnsan-gundo, Jeonbuk Province using the Automatic Weather System (AWS) of the Korea Meteorological Administration. The synthetic wind generated using the hidden Markov model will be validated by comparing statistical variables, wind energy density, seasonal mean speed, and prevailing wind direction with measurement data.

• Ocean Science Journal
• /
• v.42 no.2
• /
• pp.89-102
• /
• 2007

The surface circulation of northern South China Sea (hereafter SCS) for the period 1987-2005 was studied using the data of more than 500 satellite-tracked drifters and wind data from QuikSCAT. The mean flow directions in the northern SCS except the Luzon Strait (here after LS) during the periods October_March was southwestward, and $April{\sim}September$ northeastward. A strong northwestward intrusion of the Kuroshio through the LS appears during the $October{\sim}March$ period of northeasterly wind, but the intrusion became weak between April and September. When the strong intrusion occurred, the eddy kinetic energy (EKE) in the LS was $388cm^2/s^2$ which was almost 2 times higher than that during the weak-intrusion season. The volume transport of the Kuroshio in the east of the Philippines shows an inverse relationship to that of the LS. There is a six-month phase shift between the two seasonal phenomena. The volume transport in the east of the Philippines shows its peak sis-month earlier faster than that of the LS. The strong Kuroshio intrusion is found to be also related to the seasonal variation of the wind stress curl generated by the north easterly wind. The negative wind stress curl in the northern part of LS induces an anticyclonic flow, while the positive wind stress curl in the southern part of LS induces a cyclonic flow. The northwestward Kuroshio intrusion in the northern part of LS happened with larger negative wind stress curl, while the westward intrusion along $20.5^{\circ}N$ in the center of the LS occurred with weaker negative wind stress curl.

• Proceedings of the KSRS Conference
• /
• 2008.10a
• /
• pp.340-343
• /
• 2008

The Soya Warm Current (SWC) is a coastal boundary current, which flows along the coast of Hokkaido in the Sea of Okhotsk. Seasonal and subinertial variations in the SWC are investigated using data obtained by high-frequency (HF) ocean radars, coastal tide gauges, and a bottom-mounted acoustic Doppler current profiler (ADCP). The HF radars clearly capture the seasonal variations in the surface current fields of the SWC. The velocity of the SWC reaches its maximum, approximately 1 m/s, in the summer, and becomes weaker in the winter. The velocity core is located 20 to 30 km from the coast, and its width is approximately 50 km. The almost same seasonal cycle was repeated in the period from August 2003 to March 2007. In addition to the annual variation, the SWC exhibits subinertial variations with a period from 10-15 days. The surface transport by the SWC shows a significant correlation with the sea level difference between the Sea of Japan and Sea of Okhotsk for both of the seasonal and subinertial variations, indicating that the SWC is driven by the sea level difference between the two seas. Generation mechanism of the subinertial variation is discussed using wind data from the European Centre for Medium-range Weather Forecasts (ECMWF) analyses. The subinertial variations in the SWC are significantly correlated with the meridional wind component over the region. The subinertial variations in the sea level difference and surface current delay from the meridional wind variations for one or two days. Continental shelf waves triggered by the meridional wind on the east coast of Sakhalin and west coast of Hokkaido are considered to be a possible generation mechanism for the subinertial variations in the SWC.

• Journal of Environmental Science International
• /
• v.20 no.6
• /
• pp.737-753
• /
• 2011

The typical characteristics of seasonal winds were studied around the Pohang using two-stage (average linkage then k-means) clustering technique based on u- and v-component wind at 850 hpa from 2004 to 2006 (obtained the Pohang station) and a high-resolution (0.5 km grid for the finest domain) WRF-UCM model along with an up-to-date detailed land use data during the most predominant pattern in each season. The clustering analysis identified statistically distinct wind patterns (7, 4, 5, and 3 clusters) representing each spring, summer, fall, and winter. During the spring, the prevailed pattern (80 days) showed weak upper northwesterly flow and late sea-breeze. Especially at night, land-breeze developed along the shoreline was converged around Yeongil Bay. The representative pattern (92 days) in summer was weak upper southerly flow and intensified sea-breeze combined with sea surface wind. In addition, convergence zone between the large scale background flow and well-developed land-breeze was transported around inland (industrial and residential areas). The predominant wind distribution (94 days) in fall was similar to that of spring showing weak upper-level flow and distinct sea-land breeze circulation. On the other hand, the wind pattern (117 days) of high frequency in winter showed upper northwesterly and surface westerly flows, which was no change in daily wind direction.

• Atmosphere
• /
• v.18 no.3
• /
• pp.171-182
• /
• 2008

In this study, we analyzed the spatial and temporal distribution of wind resources over Korea based on hourly observational data recorded over a period of 5 years from 457 stations belonging to Korea Meteorological Administration (KMA). The surface and 850 hPa wind data obtained from the Korea Local Analysis and Prediction System (KLAPS) and the Regional Data Assimilation and Prediction System (RDAPS) over a period of 1 year are used as supplementary data sources. Wind speed is generally high over seashores, mountains, and islands. In 62 (13.5%) stations, mean wind speeds for 5 years are greater than $3ms^{-1}$. The effects of seasonal wind, land-sea breeze, and mountain-valley winds on wind resources over Korea are evaluated as follows: First, wind is weak during summer, particularly over the Sobaek Mountains. However, over the coastal region of the Gyeongnam-province, strong southwesterly winds are observed during summer owing to monsoon currents. Second, the wind speed decreases during night-time, particularly over the west coast, where the direction of the land breeze is opposite to that of the large-scale westerlies. Third, winds are not always strong over seashores and highly elevated areas. The wind speed is weaker over the seashore of the Gyeonggi-province than over the other seashores. High wind speed has been observed only at 5 stations out of the 22 high-altitude stations. Detailed information on the wind resources conditions at the 21 stations (15 inland stations and 6 island stations) with high wind speed in Korea, such as the mean wind speed, frequency of wind speed available (WSA) for electricity generation, shape and scale parameters of Weibull distribution, constancy of wind direction, and wind power density (WPD), have also been provided. Among total stations in Korea, the best possible wind resources for electricity generation are available at Gosan in Jeju Island (mean wind speed: $7.77ms^{-1}$, WSA: 92.6%, WPD: $683.9Wm^{-2}$) and at Mt. Gudeok in Busan (mean wind speed: $5.66ms^{-1}$, WSA: 91.0%, WPD: $215.7Wm^{-2}$).

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.6 no.3
• /
• pp.309-325
• /
• 1994

Ocean circulation in the Gulf of Alaska is remarkably constant throughout the year despite of being forced by one of the largest seasonal wind stresses in the world. To explain the small seasonal changes in the transport of Alaska Stream. a set of numerical models is employed. First a diagnostic approach is applied to reproduce circulation from the observed density structure. The results reveals the very small seasonal changes in the Alaska Stream transport. Next a series of the prognostic models is used: a barotropic model. a flat bottom baroclinic model, and baroclinic model with topography. These models reveal the influence of topography and baroclinicity on the ocean's response to the seasonal wind forcing. The intercomparisons of the various model results suggest that the seasonal response of the baroclinic ocean is primary barotropic and the resultant barotropic circulation is weakened by the scattering effect of the bottom topography.